Improvements in competition performance of national-level track and field athletes following a personalized nutrition intervention: a mixed methods approach

Abstract

Background

Personalized nutrition interventions for athletes are essential for enhancing performance and well-being, yet their effects on competition outcomes remain underexplored. This study evaluated the impact of an evidence-based, culturally appropriate personalized sports nutrition intervention on competition performance and general well-being among Sri Lankan track and field athletes.

Methods

Fourteen national-level athletes completed a 16-week nutrition intervention, during which performance data and qualitative insights were collected through face-to-face interviews at weeks 4, 8, and 16, supported by periodic telephonic follow-ups.

Results

The participants (mean age 23.0 ± 3.9 years; 57.1% male) represented sprinting, middle- and long-distance running, jumping, and throwing events. Following the intervention, participants reported reduced fatigue and enhanced performance. Many athletes also subjectively noted feeling more energetic and comfortable during training sessions, reflecting perceived improvements in general physical condition. Moreover, one athlete set a national record, six achieved personal bests, and four recorded seasonal bests during competition. They adhered to dietary recommendations and prescribed vitamins and supplements, acknowledging the importance of proper dietary habits including nutritional supplements in boosting performance. All athletes reported performance gains with respective ergogenic supplements, including caffeine (13/14), bicarbonate (3/4), creatine (3/3), beta-alanine (5/6), and beetroot juice (3/3). Five athletes reported fewer injuries and illnesses following the intervention, and two athletes reported that hydration advice enhanced their performance. Despite the positive outcomes, adverse effects were reported from the prescribed vitamins and supplements, including constipation, sleeplessness, and abdominal discomfort. Nearly all athletes expressed satisfaction with the consultation setting, intervention, assessments, and the research team.

Conclusions

This study highlights the importance of personalized, culturally specific sports nutrition interventions in improving athletic performance and general well-being.

Trial registration

The trial corresponding to this mixed-methods study was registered with the Sri Lanka Clinical Trials Registry (SLCTR/2024/013) under the Universal Trial Number (UTN): U1111-1304-8890 on 10th April 2024.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13102-025-01496-6.

Introduction

Personalized nutrition interventions tailored to athletes’ requirements have emerged as the best approach to enhancing athletic performance [1]. These strategies include practising healthy dietary habits, maintaining balanced macronutrient ratios, ensuring adequate micronutrient intake, and carefully using sports supplements and ergogenic aids. Additionally, addressing misconceptions related to sports nutrition and applying sports nutrition knowledge (SNK) to develop practical dietary patterns is crucial for fuelling physical activities, supporting recovery and repair, optimizing performance, and promoting overall health and wellness [2]. Monitoring effective nutrient timing, such as consuming carbohydrates and proteins to enhance glycogen replenishment and accelerate muscle protein synthesis, is also contingent upon maintaining proper nutrition [3]. A study by Viribay and colleagues demonstrated that consuming a high amount of carbohydrates (120 g/h) during a mountain marathon can reduce exercise-induced muscle damage, compared to carbohydrate intakes of 60 and 90 g/h [4]. Another trial reported that a whey protein supplement (25 g protein, 2.5 g fat, and 3 g carbohydrates) aids moderate improvements in acute anaerobic power and strength, indicating enhanced recovery after an intense full-body resistance training session, compared to a calorie-matched carbohydrate drink (32.5 g carbohydrates) [5]. Similarly, another randomized crossover trial involving soccer players demonstrated that pre-sleep casein protein supplementation benefits countermovement jumps recovery and reactive strength index recovery at 12- and 36-hours post-match [6]. Muscle soreness, measured using a visual analogue scale, was significantly greater in the control group (CG) compared to the casein protein group at 12 h post-match (72 ± 17 vs. 42 ± 20 mm), suggesting that casein protein supplementation may help athletes recover faster and maintain performance in subsequent training sessions or competitions [6].

In addition, vitamin supplementation has also been shown to improve sports performance. Rockwell and colleagues found that vitamin D supplementation (vitamin D3 5000 IU/day for 12 weeks) increased fat-free mass and enhanced performance in deadlift (p < 0.01) and vertical jump (p < 0.01) tests compared to controls. Baseline vitamin D status of participants was not reported, and it is unclear whether athletes were clinically deficient. Nevertheless, the observed improvements suggest that vitamin D supplementation may support strength and power performance in athletic populations [7]. A systematic review of 12 randomized controlled trials reported that iron supplementation in athletes improved performance in endurance sports [8]. Furthermore, iron supplementation may be more beneficial for athletes with ferritin levels below 20 µg/L compared to those with higher baseline ferritin levels [8].

Furthermore, dietary supplements (such as vitamins and minerals) and ergogenic aids (performance-enhancing substances such as creatine, caffeine, or beta-alanine) have been shown to enhance exercise performance and support recovery in elite athletes [9]. Various supplements and ergogenic aids have been shown to enhance exercise performance and support recovery in elite athletes [9]. For instance, a trial conducted with cyclists showed that a 6 mg·kg⁻¹ dose of caffeine consumed one hour pre-exercise significantly improved performance in 4 × 10-km time trials in the intervention group (IG) compared to the placebo group, p = 0.008 [10]. Similarly, a double-blind randomized controlled trial found that six weeks of supplementation with 4 g of creatine per day combined with electrolytes (114 mg sodium chloride, 171 mg calcium chloride, 286 mg magnesium chloride, and 171 mg potassium chloride) improved overall and repeated short-duration sprint cycling performance in male recreational cyclists [11]. The CE group showed a 4% increase in overall peak power (pre: 734 ± 75 W; post: 765 ± 71 W; p = 0.040) and a 5% increase in overall mean power (pre: 586 ± 72 W; post: 615 ± 74 W; p = 0.019;), while the placebo group exhibited no significant changes. Additionally, repeated sprint analysis revealed significant improvements in peak (pre: 737 ± 88 W; post: 767 ± 92 W; p = 0.002;) and mean power (pre: 650 ± 92 W; post: 694 ± 87 W; p < 0.001;) in the first sprint effort for the CE group [11]. In addition to caffeine and creatine, other commonly used ergogenic aids include beta-alanine. An umbrella review found that beta-alanine supplementation, with daily doses ranging from 1.2 to 7.0 g and intervention periods of 4 days to 13 weeks, generally improved exercise performance [12]. The greatest benefits were observed in exercise durations between 30 s and 10 min [12]. Furthermore, sodium bicarbonate has been shown to enhance performance in sports requiring repeated bouts of intense activity, such as sprinting, cycling, and swimming [13]. These findings are consistent with the findings of McNaughton et al., who suggest its positive effects on anaerobic capacity [14].

Although most interventions show a positive effect, they typically address only a specific component of sports nutrition practice, such as dietary modifications related to a single macronutrient or micronutrient, a sports supplement, or an ergogenic aid. However, sports performance depends on many nutritional aspects, including proper energy and macronutrient intake, addressing micronutrient deficiencies, maintaining proper hydration, and the appropriate and timely use of sports and ergogenic supplements. Furthermore, most research findings report improvements in parameters within controlled environments or focus solely on surrogate measures of athletic performance [15].

‘Real-life’ performance depends on various internal and external factors. Internal factors include physical and mental conditions, whereas external factors encompass weather and competition during the event. Consequently, quantitative parameters alone may not fully capture the impact of an intervention on a particular athlete, especially in a competitive setting. To the best of our knowledge, there are only a limited number of studies investigating the effectiveness of an evidence-based, culturally accepted, personalized sports nutrition intervention on improving sports performance during competition. Hence, our study aims to both quantitatively and qualitatively assess performance changes and explore athletes’ experiences regarding the effectiveness of an evidence-based, culturally accepted, personalized sports nutrition intervention among Sri Lankan track and field athletes.

Methods

Design and study population

This study followed a mixed-methods design, integrating quantitative performance outcomes with qualitative insights from in-depth interviews, and was guided by the COREQ reporting standards [16], as presented in Supplementary Material 1. Elite and highly trained male and female track and field athletes from the national-level athletes’ pool, who had previously completed the randomized controlled trial (RCT) of a 16-week evidence-based, culturally tailored, personalized sports nutrition intervention, were recruited for this separate study. The protocol for the original RCT has been published elsewhere [17]. Based on the calibre classification framework proposed by McKay et al. [18], all participants met the criteria for Tier 4, as they competed at the international level (international/elite). Some athletes also met the criteria for Tier 3 (national/highly trained), as they regularly competed at national championships and represented the highest competitive standard within Sri Lanka. None of the participants had received formal, individualized nutrition counselling prior to the original RCT. A total of 14 athletes successfully completed the original RCT and were therefore eligible for inclusion in this qualitative study. Informed written consent was obtained from each participant after an in-depth explanation of the study, with adequate time provided for questions and clarification. All methods were conducted in accordance with the Declaration of Helsinki. Ethical approval was obtained from the Institutional Ethical Review Committee, Faculty of Medicine, University of Peradeniya, Sri Lanka (2024/EC/21).

Intervention

The principal investigator delivered an evidence-based, culturally tailored, and personalised sports nutrition intervention adapted to each athlete’s sporting background. Cultural tailoring involved aligning nutrition advice with local dietary practices, traditional food preferences, food availability, sociocultural eating patterns, and religious dietary restrictions (e.g., vegetarianism, avoidance of beef or pork). Economic accessibility and individual preferences for meal timing and composition were also considered. For example, some athletes preferred larger lunches and lighter dinners due to late-evening training, while others required carbohydrate-rich snacks 60–90 min before training to support energy availability. Consultations additionally covered intra- and post-workout refuelling strategies appropriate for morning and afternoon training schedules. All one-on-one sessions were conducted at baseline (week 0), week 4, and week 8, with each consultation lasting approximately 15–30 min depending on the complexity of the dietary issues identified. This duration was regarded sufficient to achieve thematic depth while remaining feasible within athletes’ training commitments.

Between weeks 8 and 10, weekly sports nutrition education materials from the national sports nutrition guidelines [19] were shared via WhatsApp (WhatsApp LLC, Meta Platforms, Inc.), accompanied by regular communication to address questions and provide follow-up support. From weeks 10 to 16, athletes received a structured online sports nutrition education program, consisting of ten weekly chapters from a comprehensive guideline [19], covering both general and sports nutrition knowledge. These materials were delivered in text and PDF formats in Sinhalese and Tamil. A trained research assistant also conducted weekly checks and brief quizzes via WhatsApp to reinforce compliance and clarify uncertainties. The primary nutrition-related areas covered throughout the process included:

1. Energy intake: Athletes were advised to consume sufficient energy based on their overall energy balance. Requirements were estimated qualitatively by the principal investigator (RJ), taking into account training volume and intensity, body size, observed appetite cues, meal patterns, and performance or fatigue indicators. Portion recommendations for each food item were provided using culturally acceptable portion sizes. Formal mathematical calculations were not employed due to practical constraints; instead, adjustments were made through continuous monitoring of training load, weight stability, and athlete-reported energy levels. When energy intake needed to be adjusted, culturally familiar foods were emphasized; for example, increasing rice portions, incorporating traditional snacks, or reducing high-fat curries, ensuring that guidance was practical and contextually appropriate. In cases where dietary modifications alone were insufficient to meet energy needs, energy-containing supplements were prescribed to bridge the gap. Conversely, athletes with high adiposity and excess energy intake received culturally specific advice to reduce calorie intake [20].

2. Carbohydrate intake: Advice on carbohydrate intake was provided according to recent guidelines [21] and locally common carbohydrate sources (e.g., red rice, string hoppers, manioc, jackfruit) were recommended.

3. Protein intake: Advice was provided according to established guidelines [22], recommending culturally familiar high-protein foods such as lentils, eggs, dried fish and chicken. The recommended total daily protein intake was calculated at 1.2–1.6 g/kg of body weight, with each meal containing 0.3–0.4 g/kg of body weight, thereby necessitating four protein-rich meals per day. When athletes could not meet the recommended protein intake, whey protein supplements were prescribed.

4. Fat intake: Foods high in saturated fats, such as coconut oil, coconut milk, and coconut sambal, were discouraged, and coconut oil was substituted with healthier unsaturated oil such as extra virgin olive oil, gingelly oil, and sunflower oil. For participants consuming insufficient amounts of fish, especially those not eating oily fish at least twice per week, a daily supplementation of 1000 mg of omega-3 fish oil was prescribed. Participants were advised to limit or avoid consuming deep-fried foods, oily street foods, and high-fat sweets such as chocolate.

5. Micronutrients: Advice focused on optimising dietary intake, and micronutrient supplements were prescribed only for athletes with biochemically confirmed deficiencies. All supplements were prescribed by the principal investigator, a medically qualified consultant in clinical nutrition, under routine clinical supervision. Vitamin D insufficiency or deficiency was treated by prescribing either 60,000 IU weekly, and/or 5,000 IU, 2,000 IU, or 1,000 IU daily (Alvin Andersen Distributors, INC., based in Hialeah, Florida), depending on the blood values [23]. In cases of iron deficiency, identified through low serum ferritin or anaemia, oral iron supplements (Ferrous Fumarate BP 300 mg, equivalent to 100 mg elemental iron) were prescribed to be taken once daily. These supplements were not provided to athletes without biochemical evidence of deficiency. Additionally, multivitamin-multimineral supplements (Menuvit; Finecure Pharmaceuticals Limited) and calcium supplements (Ascal: Calcium Carbonate 450 mg, Vitamin C 40 mg, Vitamin D₃ 200 IU) were provided to all athletes. Due to financial constraints and limited laboratory resources, it was not feasible to assess biochemical deficiencies for vitamins and minerals beyond iron. Furthermore, Sri Lanka, as a lower-middle-income country, has documented low population-level intake of fruits and vegetables and disproportionately high consumption of refined starches and added sugars [24]. Considering these contextual dietary patterns and the increased micronutrient demands of athletes, empirical supplementation was implemented as a precautionary measure to support overall micronutrient adequacy.

6. Intake of fibre: Participants were encouraged to consume grains, fruits, vegetables, nuts, and legumes as part of a healthy diet [25]. However, high-fibre foods were discouraged immediately before training and competitions to minimize gastrointestinal discomfort, bloating, and potential negative effects on performance [26].

7. Hydration: Personalised hydration advice was provided based on each athlete’s hydration status, assessed using urine specific gravity (USG), urine colour, and thirst. Assessments were conducted at baseline, week 4, and week 8, with weekly monitoring via WhatsApp throughout the intervention.

8. Ergogenic supplements: Different ergogenic supplements were prescribed in accordance with the International Olympic Committee (IOC) guidelines [9], and were verified for safety and quality through product labelling and certificates of analysis provided by the manufacturer. Athletes were instructed to source supplements from reputable suppliers to ensure adequacy and minimize contamination risk. Caffeine tablets (Caffeine 200 mg, 180 Tablets; Naturheilpraxisbedarf Andrös, Germany) containing 200 mg of caffeine per tablet were recommended 30–60 min before training and competitions. Athletes generally consumed one tablet (200 mg) based on individual tolerance and session demands. Sprinters, jumpers, and throwers were advised to take 3–5 g of creatine monohydrate daily, while beta-alanine was recommended for 400 m and 800 m runners. Sodium bicarbonate was recommended before competitions for selected athletes to buffer acid accumulation and delay fatigue during high-intensity efforts. Beetroot juice was recommended for long-distance runners to enhance endurance performance through improved nitric oxide availability and oxygen efficiency. Commercial pre-workout supplements were not recommended due to their multi-ingredient formulations and the increased risk of contamination with unwanted or undeclared substances.

Data collection

Qualitative approach

Qualitative data were collected through face-to-face in-depth interviews at weeks 4, 8, and 16. Information from all three interviews was compiled into a single document for each participant. Trained research assistants conducted the interviews using a pre-designed guide (Supplementary Material 2) with open-ended, semi-structured questions to ensure consistency. The interviews covered five themes: (1) dietary changes, (2) prescribed vitamins and supplements, (3) the consultation setting, (4) changes in sports nutrition knowledge and performance, and (5) prescribed ergogenic supplements. Interviews were conducted in the participants’ native language (Sinhalese or Tamil) and recorded. Interviewers guided discussions and ensured constructive, focused responses while remaining neutral. The principal investigator was deliberately excluded to minimize bias. The study followed a directed content analysis approach, providing a structured framework for theme identification and interpretation. Data collection continued until data saturation was achieved, ensuring comprehensive coverage of participant experiences. Transcripts were not returned to participants for correction, but consistent follow-up discussions allowed clarification of key points.

Research team and reflexivity

Two trained female full-time research assistants (one with a BSc in Physiotherapy and one with an MBBS) conducted the interviews. Both had prior experience in qualitative interviewing and received project-specific training before data collection. They had no prior relationship with participants, who were informed that the interviewers were independent and had no involvement in the nutrition intervention or performance assessments. The principal investigator deliberately remained uninvolved in the interviews to avoid influencing participants’ responses, as they might have been reluctant to share negative feedback with him. The interviewers maintained neutrality throughout and followed standardised procedures to minimise bias.

Quantitative approach

In addition to in-depth interviews, telephonic conversations were conducted during and after training and competitions to gather athlete-reported feedback on training and performance outcomes. The number of these conversations varied between athletes, as follow-ups were undertaken after each individual competition and during several selected training sessions. Questions were framed to allow neutral, open responses (e.g., “Did you notice any changes in your training or competition performances?”), and athletes were free to describe positive, negative, or unchanged outcomes.

Data analysis and rigour

A directed content analysis approach was applied using pre-determined categories aligned with the study objectives, consistent with the methodology described by Hsieh and Shannon [27]. These categories guided the initial coding and organisation of themes. Two researchers independently coded all transcripts, and any discrepancies were resolved through discussion until consensus was reached. A senior researcher was consulted if disagreements persisted. Themes were developed through an in-depth examination of coded data, enabling the identification of key patterns and relationships within the dataset. The verbal responses from each participant were analysed using interview notes and audio recordings. Immediately after each interview, the research team documented key information and cross-checked their notes with the recordings. Each interview produced a detailed document that was reviewed collectively at the end of the study. After translation and transcription, participants received a brief summary of their responses for confirmation (member checking), and minor clarifications were incorporated into the final transcripts. Interviews were originally conducted in Sinhalese and Tamil, then translated into English by independent translators. The research team, with support from the translators, compared and refined the translations through an iterative consensus process to produce the final written transcript.

Results

Participants

Fourteen elite and highly trained track and field athletes (Tier 3–4 according to the McKay et al. [18] framework), representing both genders and recruited from across the country, participated in the study. The mean age of the athletes was 23.0 ± 3.9 years, with a mean sports experience of 7.2 ± 3.5 years. The sample included 57.1% males and 42.9% females. Athletes represented five track and field disciplines: six sprinters (3 M, 3 F), two middle-distance runners (1 M, 1 F), three long-distance runners (2 M, 1 F), two jumpers (1 M, 1 F), and one thrower (F). According to performance level, five athletes (35.7%) were elite, while nine athletes (64.3%) were highly trained. The highest education levels achieved by the participants included: 35.7% had completed primary education (ten years of school education), 50.0% had completed secondary education (13 years of school education), and 14.3% had completed or were enrolled in a university degree or diploma program.

Findings of the dietary assessment

After the 16-week evidence-based sports nutrition intervention, athletes demonstrated significant improvements in energy intake as well as several macro- and micronutrient parameters (Table 1). Participants showed significant increases in energy (+ 1206.9 kcal, p = 0.007), protein (+ 21.25 g, p = 0.003), polyunsaturated fatty acids (PUFA; +9.67 g, p = 0.002), fibre (+ 2.63 g, p = 0.037), vitamins A (+ 828.57 µg, p = 0.002), B1 (+ 5.00 mg, p = 0.001), B2 (+ 4.20 mg, p = 0.001), C (+ 95.91 mg, p < 0.001), and E (+ 7.21 mg, p < 0.001), as well as calcium (+ 398.09 mg, p < 0.001) and iron (+ 23.86 mg, p < 0.001). Energy and nutrient intakes increased in athletes who had previously under-consumed, while those with excess intake reduced accordingly. Individual analyses ensured that adjustments matched nutritional requirements. The observed increases in calcium and iron also reflected the prescribed supplementation protocol. Overall, body weight remained stable (mean change: +0.3 ± 0.7 kg), indicating that intake modifications supported performance goals without creating an excessive caloric surplus.

Table 1.

Pre- and post-intervention changes in dietary nutrients, vitamins, and minerals among athletes

Variable		Mean ± SD(n=14)
	Pre	Post	Change	p-value
Energy (kcal)	2766.0±494.0	3972.9±934.4	+1206.9	0.007
Carbohydrate (g)	441.2±52.1	475.3±132.9	+34.1	0.373
Carb % (%)	62.62±7.2	61.44±6.6	−1.18	0.132
Protein (g)	95.56±30.2	116.81±41.8	+21.25	0.003
Protein % (%)	13.10±2.1	15.26±3.6	+2.16	0.006
Fat % (%)	24.36±5.3	20.10±4.0	−4.26	0.477
DF (g)	16.53±8.7	19.16±11.1	+2.63	0.037
PUFA (g)	9.75±3.6	19.42±4.5	+9.67	0.002
Vitamin A (µg)	891.33±520.3	1719.90±833.5	+828.57	0.002
Vitamin B1 (mg)	3.65±1.3	8.65±5.1	+5.00	0.001
Vitamin B2 (mg)	3.88±1.8	8.08±2.3	+4.20	0.001
Vitamin B6 (mg)	2.71±1.7	7.35±4.4	+4.64	0.001
Folic Acid (µg)	92.20±30.3	221.28±84.6	+129.08	<0.001
Vitamin C (mg)	58.25±40.8	154.16±74.9	+95.91	<0.001
Vitamin E (mg)	6.15±3.9	13.36±5.9	+7.21	<0.001
Sodium (mg)	3405.8±1364.52	4325.4±1362.30	+919.60	0.021
Potassium (mg)	2501.2±942.2	5064.3±977.3	+2563.1	0.028
Calcium (mg)	586.41±260.3	1184.5±550.8	+398.09	<0.001
Magnesium (mg)	259.43±158.4	489.90±189.3	+130.47	<0.001
Phosphorus (mg)	1633.6±414.7	3711.3±563.7	+2077.7	0.017
Vitamin D (µg)	35.92±101.2	62.81±104.2	+26.89	<0.001
Iron (mg)	20.81±6.8	44.67±88.9	+23.86	<0.001
Zinc (mg)	22.25±16.7	40.94±21.4	+18.69	0.049

 IG Intervention group, SD  Standard deviation, kcal Kilocalories, g  Grams, mg  Milligrams, µg Micrograms, DF Dietary fibre,  PUFA  Polyunsaturated fatty acids, %  Percentage

Findings from the quantitative approach

The quantitative data (Table 2) indicate notable performance gains during the intervention period. One athlete set a new national record, and six of 14 athletes (43%) achieved competition personal bests (PBs), with 1RM improvements ranging from 2 to 10 kg (5–15%), depending on the exercise and individual training status. An additional four athletes (29%) recorded seasonal bests (SBs), demonstrating meaningful improvements even among those who did not achieve PBs. In training sessions, most athletes (12/14; 86%) reported achieving PBs, although some gains did not fully translate into competition outcomes. In resistance training, 11 of 14 athletes (79%) achieved clear improvements in 1RM across key exercises, with sprint and power athletes showing gains at the upper end of the range (~ 10–15%). Only three long-distance runners did not report improvements in resistance-training PBs, likely due to their predominantly endurance-focused training. Overall, all athletes (14/14; 100%) reported “feeling better,” reflecting enhanced recovery, readiness, or performance perception.

Table 2.

Summary of performance improvements observed among participants following the intervention

Participant characteristics	Competition PB achieved	Competition SB achieved	Training PB achieved	PB during resistance training achieved	Feeling better	No change
M, 23 y, 5000 m			x	NA	x
M, 25 y, 800 m			x	x	x
F, 23 y, high jump			x	x	x
M, 26 y, 5000 m, 10 000 m	x			NA	x
M, 26 y, 400 m	x			x	x
M, 20 y, 400 m hurdles		x		x	x
M, 25 y, 110 m hurdles				x	x
M, 21 y, High jump		x		x	x
M, 22 y, 800 m	x			x	x
F, 28 y, 100 m hurdles	x			x	x
F, 21 y, Hammer throw		x		x	X
F, 22 y, 5000 m, 10 000 m	x*			NA	X
F, 21 y, 400 m hurdles			x	x	X
F, 19 y, 400 m	x			x	X

F  Female,  M Male, PB Personal Best, SB Seasonal Best

* Set a new national record

Findings from the in-depth interviews

In-depth interviews designed around five themes to qualitatively explore athletes’ experiences with the effectiveness of the personalized sports nutrition intervention. Interviews lasted approximately 10–15 min per theme (total 30–45 min per athlete). This duration was considered sufficient to achieve depth while maintaining participant engagement within the constraints of athletes’ training schedules. The key findings for each theme are presented in Table 3.

Table 3.

Key qualitative themes and representative quotations describing athletes’ experiences with the sports nutrition intervention

Theme	Key findings	Illustrative quotes
1. Experience with the dietary advice	Most athletes followed the recommendations and reported positive impacts on energy, well-being, and training performance; common dietary changes included pre/post-training meals, increased protein intake, and healthier fat sources; a few faced challenges (e.g., time, taste)	-“I started eating a banana before training and drank milk after.” (M, 25)
2. Opinion on the prescribed vitamins and supplements	Athletes viewed supplements as beneficial for energy, performance, recovery, and injury prevention; some experienced side effects (e.g., constipation, gastritis) which were managed with adjustments	-“I didn’t take any vitamins earlier, but now I feel like I have more energy.” (M, 23)
3. Opinion on the consultation setting	Athletes expressed high satisfaction with consultations, advice, and medical testing; some wanted longer consultations or more detail initially, which was addressed in follow-ups	-“I haven’t followed sports-specific dietary advice like this before… my knowledge about nutrition has improved a lot.” (M, 25)
4. Opinion on changes in sports nutrition knowledge and performance	All athletes reported improved energy, recovery, reduced fatigue and injuries, better hydration practices, and enhanced performance	-“My timing has improved, I feel less tired, and I have more energy.” (M, 25)
5. Opinion on prescribed ergogenic supplements	Most athletes reported performance benefits from supplements (e.g., caffeine, bicarbonate, creatine, BA, beetroot juice); some experienced side effects like nausea, loose stools, sleep disturbances; adverse effects were managed	-“I have improved my throwing distance by 4 meters because of the caffeine.” (F, 21)

F  Female,  M  Male, BA Beta-alanine

Theme 1: experience with the dietary advice

Most athletes reported being able to follow nearly all dietary recommendations provided by the principal investigator and appreciated how these changes improved their well-being. Several athletes adopted new nutrition-related behaviours, which they felt had a positive impact on their health. One athlete shared,

“I didn’t eat anything before and immediately after training but after the sports nutritionist’s advice. I started eating a banana before my training and also drank a packet of milk after the training” (Middle-distance runner, M, 25 years).

Another participant noted,

“I didn’t take dates or ORS (Jeewani) during training before. But now, since the sports nutritionist prescribed them, I do. Only after making these changes, I have been able to fully perform my workouts with much more energy” (Long-distance runner, M, 23 years).

Similarly, another athlete stated,

“I followed all the dietary advice given by the sports nutritionist. I ate a sandwich and drank a glass of milk before training. After training, I have a banana and a protein bar” (Sprinter, M, 26 years).

In addition, many athletes reported that they had incorporated boiled eggs into their post-training meals as a convenient protein source along with their meals, especially in the morning when they can’t find any cooked fish or meat, finding it an easy way to increase their protein intake. As one sprinter mentioned,

“The sports nutritionist asked me to take eggs, which I did” (Sprinter, F, 19 years).

Another added,

“I have included eggs with rice and curry immediately after my training now.” (Long-distance runner, M, 23 years).

All the athletes reported replacing coconut oil either with extra virgin olive oil or gingelly oil, as recommended by the principal investigator. Some athletes opted for gingelly oil instead of olive oil due to financial constraints.

“I also added extra virgin olive oil to my diet.” (Jumper, M, 21 years).

A notable benefit reported by the athletes was an improved sensation of hunger due to the proper pre-training meal advice.

One athlete stated,

“I feel much more comfortable training now. I don’t feel hungry during training like I did before” (Long-distance runner, F, 22 years).

Another sprinter mentioned feeling more energetic and less lethargic during training due to the dietary changes, saying,

“I feel comfortable and fit while running. Earlier, I had body pain and tiredness, but now that’s gone.” (Sprinter, F, 19 years).

Additionally, one sprinter highlighted the improvement in her sleep quality, attributing it to the prescribed diet plan, which included taking a scoop of whey protein before bedtime. She commented,

“I feel so much better in my body. Earlier, I used to get hungry late at night because of what I ate for dinner, but that’s not the case now” (Sprinter, F, 28 years).

Moreover, a hammer thrower, who had been advised to reduce her caloric intake due to being obese (body fat 37.8%), reported feeling much more comfortable during training after losing a few kilograms. She stated,

“I feel so relaxed in my body because the sports nutritionist asked me to reduce my rice intake and increase green vegetables. This change has greatly improved my training, and I have been recording greater distances than before” (Hammer thrower, F, 21 years).

On the other hand, a few athletes noted challenges in fully complying with the dietary recommendations due to practical constraints such as time limitations.

One long-distance runner mentioned,

“The sports nutritionist also asked me to eat boiled chickpeas in the morning on some days, but I didn’t have enough time to cook that” (Long-distance runner, F, 22 years).

Another long-distance runner experienced initial discomfort when consuming extra virgin olive oil, as it was unfamiliar to him.

He shared,

“It was initially hard to take it because of the bitter taste” (Long-distance runner, M, 23 years). But subsequently, he could tolerate it.

Theme 2: opinion on the prescribed vitamins and supplements

All participants (14/14) recognized the significant importance of the recommended multivitamin, multimineral, and sports supplements in enhancing their sports performance, recovery, reducing injury risk, and overall well-being. They also expressed positive feedback regarding the prescribed vitamins and supplements, detailing the beneficial effects they experienced from the supplementation. While athletes attributed performance improvements to the recommended supplements, these benefits may also reflect improved fuelling behaviours adopted during the intervention.

One participant noted,

“I didn’t take any vitamins earlier, but with these vitamins and supplements, I feel like I have more energy. I can run so well now” (Long-distance runner, M, 23 years).

Another participant commented,

“I feel so fit. I no longer have the laziness I had earlier. I’m much quicker now, and my timing has also improved. I ran really well in the morning sessions” (Sprinter, M, 26 years).

Despite the positive feedback, some athletes experienced adverse effects from the prescribed vitamins and supplements, including constipation and abdominal discomfort. One athlete reported,

“I got a bit of gastritis from the multivitamin and iron tablets " (Hammer thrower, F, 21 years).

Another stated,

“I had constipation because of the whey protein. I couldn’t pass stools for three days straight, and because of that, I experienced bloating in my stomach” (Sprinter, F, 28 years).

Additionally, a jumper experienced vomiting after the first day of whey protein intake during training, stating,

“I vomited on the very first day of taking the whey protein during training, but I don’t feel nauseous when taking the protein now” (Jumper, M, 21 years).

The research team closely monitored athletes who reported adverse effects. They received guidance on mitigating these effects, such as consuming iron with a main meal, avoiding protein supplements early in the morning, or using medications for those with gastric discomfort. During follow-up consultations, all affected athletes (3/3) reported that they did not experience such side effects afterwards.

Additionally, upon reviewing the medical history of the sprinter who experienced abdominal bloating and constipation due to whey protein supplementation, it was found that she had milk food intolerance. Consequently, she was advised to switch to a non-dairy protein, such as a beef-based protein supplement, and the problems were resolved.

Theme 3: opinion on the consultation setting

Most respondents were satisfied with the sports nutrition intervention and valued the dietary advice provided by the principal investigator. They also appreciated the increase in their nutrition knowledge gained during the consultations.

“I haven’t followed sports-specific dietary advice like this before. After this program, I feel my knowledge about nutrition has improved a lot.” (Middle-distance runner, M, 25 years).

“The explanations are enough. Since the sports nutritionist allowed me to record his advice, I got the chance to go home and listen to the missed points.” (Middle-distance runner, M, 22 years).

This opportunity to re-listen to the recorded consultation also supported the educational component of the intervention, helping athletes reinforce and consolidate missed information. All the athletes also expressed great satisfaction with the tests and investigations they underwent as part of the sports nutrition intervention and highly appreciated the efforts made by the research team.

“Those tests were essential. From those tests, I learned that the fat percentage of my body is higher than normal.” (Middle-distance runner, M, 22 years).

Another sprinter commented that,

“Yes, those tests were really important. From them, I learned that my haemoglobin has been low.” (Sprinter, F, 28 years).

The feedback provided during these assessments contributed further to the educational aspect of the intervention, enhancing athletes’ understanding of their nutritional status and body composition.

Another athlete acknowledged the importance of the SNK he acquired through participating in the intervention.

“I got to know many important facts that I didn’t know earlier. The sports nutritionist said that I’m drinking an excess amount of water looking at my urine specific gravity values, so I stopped that practice as well.” (Sprinter, M, 20 years).

In contrast, a few participants (3/14) reported that they would have appreciated extended consultation times and more detailed explanations of the dietary advice.

“I feel it would be better if the sports nutritionist could explain more about how to take food throughout a given day.” (Sprinter, M, 26 years).

“I feel like it would be great if I could get more time for my consultation.” (Sprinter, F, 28 years).

However, this feedback was incorporated into the subsequent interviews, and consequently, they were satisfied with the duration of the following consultation.

Theme 4: opinion on the changes observed in sports nutrition knowledge and performance

All athletes (14/14) reported feeling better and experiencing reduced fatigue following the sports nutrition knowledge component, which was integrated into every personalised consultation. SNK concepts were taught throughout the entire intervention and applied directly to athletes’ diets and performance goals, with additional materials distributed via WhatsApp after Week 8.

“My timing has improved, I feel less tired, and I have more energy.” (Middle-distance runner, M, 25 years).

“Yes, I have more energy now. I can perform better compared to before.” (Jumper, F, 23 years).

Another middle-distance runner noted that his recovery had significantly improved following the implementation of the sports nutrition strategies.

“I felt a great advantage from the diet recommended by the sports nutritionist. I feel like my recovery has improved after a heavy workout.” (Middle-distance runner, M, 22 years).

A marathoner commented that the hydration and dietary advice he followed after the sports nutrition intervention enhanced his performance.

“Earlier, I didn’t drink enough water and didn’t eat properly. With this dietary advice, I see a significant improvement in energy levels.” (Marathoner, M, 23 years).

Additionally, some athletes reported experiencing fewer injuries and illnesses after following the prescribed dietary advice and supplementation. These changes were observed during the pre-competition and early competitive phase of the annual training cycle, when athletes were preparing for key national championships.

“Earlier, I used to get sick frequently, but now that’s not the case. I can do my training so well now. I feel very fit and experience less fatigue.” (Jumper, M, 21 years).

Another middle-distance runner mentioned that,

“Earlier, I had Achilles tendon pain frequently, but now it is very rare.” (Middle-distance runner, M, 22 years).

Theme 5: opinion on the prescribed ergogenic supplements

Based on the specific ergogenic supplements prescribed for each athlete, depending on their main sports event, the athletes reported mixed opinions regarding the beneficial effects and adverse side effects they experienced. Regarding the use of caffeine, nearly all athletes (13/14) reported improvements in their sports performance, particularly in terms of timing and increased energy levels.

“I have improved my throwing distance by 4 meters because of the caffeine. I also feel more energetic.” (Hammer thrower, F, 21 years).

One sprinter reported achieving his personal best during a tournament after introducing caffeine supplementation. However, this improvement reflects the athlete’s perception and may also be attributable to the overall intervention, including improved fuelling strategies and ongoing training progression.

“My timing has improved because of caffeine. Earlier, my personal best was 1:53.00 for 800 m, but I achieved 1:51.20 at the Junior National meet, and I placed first.” (Middle-distance runner, M, 22 years).

Another athlete also recorded her best performance after using caffeine before competition. While athletes linked these improvements to caffeine, the gains may also reflect concurrent progress in training, nutrition, and fuelling strategies. As she explained:

“I got my best timing for the 400 m with 59.7 seconds; initially, it was over 60 seconds. In the 800m, I ran 2:27 seconds compared to my previous time of 2:44 seconds. I won first place in both events at the zonal meet.” (Sprinter, F, 19 years).

However, some athletes reported adverse effects, including difficulty sleeping after consuming caffeine in the morning. One athlete explained:

“I couldn’t sleep on the days I took caffeine. Previously, I used to sleep around 8–9 PM, but now I’m awake until 12 − 1 AM” (Sprinter, F, 21 years).

Regarding bicarbonate use, most athletes (3 out of 4) who were advised to take it reported positive effects on their sporting performance.

“I think bicarbonate was very beneficial for me. After using it, I felt no tightness in my legs during running, and my timing improved” (Middle-distance runner, M, 22 years).

However, two athletes experienced side effects such as loose stools, bloating, and nausea following bicarbonate supplementation.

“I felt nauseous when I took bicarbonate on the first day of training. My coach advised me to take a break and try it again after a couple of days” (Sprinter, M, 26 years).

Athletes prescribed creatine (3/3) demonstrated notable improvements in explosive power compared to earlier performances. The hammer thrower reported significant performance gains following creatine supplementation, with the athlete now achieving a throw of 42 m, up from her previous seasonal best of 40 m.

“I’m now recording greater distances than before; previously, my best throw was 38 meters in my last meet, but now I have reached 42 meters during training” (Hammer thrower, F, 21 years).

Similarly, a sprinter reported improved energy levels and better performance during morning workouts, attributing these gains to the overall nutrition intervention rather than a single supplement. As he noted:

“Earlier, I felt less energetic for morning workouts. It was really hard for me to perform plyometrics and explosive exercises” (Sprinter, M, 25 years).

Regarding BA supplementation, most athletes (5/6) noted a positive impact. One sprinter reported feeling much fitter and more energetic during training, along with improved timing.

“I think the BA has started to work because my timing is perfect now.” (Middle-distance runner, M, 22 years).

Additionally, beetroot juice was recommended for three athletes. Those already consuming it were advised to improve the preparation to ensure sufficient dietary nitrate intake. This included using an adequate quantity of beetroot and enhancing the nitrate content by adding leafy greens such as spinach and celery, which are affordable and locally available sources of nitrates. One athlete shared:

“I used to drink beetroot juice, and sir asked me to mix in spinach leaves and celery. It’s easy for me since they’re readily available near my residence” (Long-distance runner, M, 23 years).

Athletes who experienced side effects from ergogenic supplementation were prescribed medications to relieve their symptoms by the principal investigator and were closely monitored for improvements.

Discussion

This study aimed to assess the effectiveness of an evidence-based, culturally specific personalized sports nutrition intervention quantitatively and qualitatively in improving the performance and well-being of professional track and field athletes in Sri Lanka. To the best of our knowledge, this is the first study to demonstrate real-life competition performance improvements following a personalized sports nutrition intervention. Our findings highlight the effectiveness of personalized nutrition advice in enhancing performance, as one participant set a national record, six achieved personal bests (PBs), four recorded seasonal bests (SBs), and all athletes reported improved well-being and reduced fatigue. Notable strength-related improvements were observed, with average increases of 5–15% in one-repetition maximum (1RM) exercises, particularly among sprinters, jumpers, and throwers, reflecting measurable physiological adaptations from combined dietary optimization and evidence-based supplementation. In line with these performance outcomes, notable improvements were also observed in strength-related measures. Most athletes demonstrated meaningful gains in their one-repetition maximum (1RM) across key resistance-training exercises, with average increases ranging from 5% to 15% over the intervention period. These improvements were particularly evident among sprinters, jumpers, and throwers, who generally reported increases at the upper end of this range. Such gains suggest that the combined dietary optimization and evidence-based supplementation not only enhanced competition performance but also contributed to measurable physiological adaptations relevant to strength and power development.

The distinctiveness of this study lies in its focus on elite athletes who had not previously received structured nutritional guidance, making it particularly relevant for resource-limited settings. Optimizing calorie intake, protein, and micronutrients can enhance both performance and general well-being, especially among athletes from low socioeconomic backgrounds with suboptimal diets. Participants were also advised on replacing high-saturated fats with unsaturated oils and limiting deep-fried foods, consistent with evidence showing benefits for musculoskeletal health and reduced inflammation.

The current study demonstrated significant performance improvements in most participants, which can be attributed to the personalized dietary advice provided. This included consuming sufficient calories, macronutrients, and micronutrients, as well as practicing evidence-based use of ergogenic supplements. Low energy availability is very common among athletes and is correlated with decreased testosterone levels, reduced bone density, and a lower resting metabolic rate, which negatively impact performance and general well-being [28]. Many Sri Lankan athletes come from low socioeconomic backgrounds and exhibit poor dietary practices [29]. Optimizing calorie intake in this population may enhance both performance and overall well-being. Additionally, adequate protein intake, along with appropriate dietary planning, has been shown to improve performance [30]. Sri Lankan diets are predominantly high in saturated fat, primarily derived from coconut [31]. Saturated fats are known to affect negatively affect musculoskeletal tissues [32]. All athletes were instructed to replace high-saturated coconut oil with high-unsaturated oil sources such as either EVOO or gingelly oil. Several studies suggest that EVOO, rich in phenolic compounds, exhibits beneficial biological effects due to its antimicrobial, antioxidant, and anti-inflammatory properties [33]. Furthermore, supplementation with EVOO has been found to improve cardiorespiratory coordination during moderate-intensity exercise compared to palm oil [34]. Participants were also advised to limit or avoid consuming deep-fried and oily street foods, as the literature indicates that trans fats increase inflammation [35]. Post-intervention dietary assessments showed a reduction in fried food consumption and improved fat quality. Athletes reported replacing fried items with healthier fats, such as nuts, seeds, and minimally processed oils, reflecting a shift toward anti-inflammatory dietary patterns.

Micronutrients are essential for athletic performance and overall health, supporting energy metabolism, protein synthesis, oxygen transport, bone health, immune function, and electrolyte balance [36]. Vitamin D deficiency is common among athletes, and supplementation can reduce post-exercise biomarkers in endurance runners [37]. In our study, vitamin and mineral supplements were prescribed only when biochemical deficiencies were identified. Iron deficiency, also common and independently linked to reduced performance [38], was treated with oral iron. All athletes received a therapeutic dose of a multivitamin, with additional supplements (e.g., vitamin D, iron) provided only when testing indicated a need. While evidence suggests that long-term multivitamin use does not consistently enhance performance in well-nourished populations [39, 40], and routine supplementation is generally not recommended, many Sri Lankan athletes face suboptimal diets due to economic and social constraints [41]. In such low-resource settings, multivitamin supplementation may help address deficiencies and support athletes in reaching their full performance potential.

Our findings on improved performance with caffeine and other ergogenic aids align with existing literature [42], which demonstrates that these supplements can enhance endurance, strength, and alertness in sport-specific contexts. This supports the role of evidence-based supplementation within personalized nutrition interventions in contributing to measurable performance gains among track and field athletes. Creatine monohydrate is another widely recognized supplement that has been shown to enhance strength, power, and high-intensity exercise performance [43]. Research suggests that creatine supplementation increases the availability of phosphocreatine in muscles, enabling athletes to sustain high-intensity efforts for longer periods, which is crucial for sprinters, jumpers, and throwers. The recommended dosage of 3–5 g of creatine monohydrate in this study follows the standard practice established in the literature [44], with numerous studies demonstrating its efficacy in improving power output and athletic performance, particularly in explosive activities. BA, another key supplement recommended in the current study for middle-distance runners (400 m and 800 m), has been shown to enhance performance by buffering lactic acid accumulation, thereby delaying fatigue. Sodium bicarbonate, prescribed for selected athletes, is also known for its ability to enhance performance by neutralizing the acid build-up during high-intensity, short-duration efforts [45]. Finally, beetroot juice, recommended for long-distance runners in the current study, has gained attention for its potential to enhance endurance performance due to its high nitrate content [46].

Previous research has demonstrated that certain physical performance indicators significantly improve among athletes following sports nutrition interventions, though not all parameters exhibit the same extent of improvement. For example, a trial conducted on elite athletes to evaluate the effects of nutritional guidance reported improvements in all one-repetition maximum tests in both groups (6–12%), but no significant changes in the 40 m sprint or countermovement jump [47]. Compared to our findings, Garthe et al. reported modest results, likely because their participants were better nourished than those in our sample, who had not previously received professional sports nutrition support and were from a developing country.

Similarly, another study reported improvements in jump and squat performance as well as 5–10−5 shuttle times among basketball players following a 90-minute sports nutrition education intervention, observed from pre- to post-intervention [48]. However, no significant differences were noted between the IG and CG. To reinforce the intervention, additional 45-minute sessions were conducted every three weeks in small groups of five players at the university dining hall [48]. Although Rossi and colleagues employed a mixed methods approach similar to our research, the observed improvements were not as significant as those in our study. The dual approach used in our intervention, which combined individualized support with online guidance, likely played a critical role in the enhanced performance outcomes. Continuous individual support, regular monitoring through online platforms, and tailored advice on both general and sports nutrition allowed athletes to actively engage with the intervention. Furthermore, enabling them to record all guidance provided by the principal investigator through their smartphones may have significantly contributed to the superior performance improvements observed in our study compared to others.

A key strength of the present study is its combination of culturally tailored, evidence-based, individualized dietary and supplement guidance, which aligns well with the needs of athletes and enhances their engagement. Additionally, the real-life assessment of this intervention allowed us to evaluate its impact on both competition performance and the general well-being of track and field athletes in Sri Lanka. Additionally, the use of both quantitative metrics (e.g., performance improvements, strength gains) and qualitative feedback provides a comprehensive view of the intervention’s impact. The study also acknowledges challenges, such as time constraints for food preparation and taste aversion, which are common in dietary interventions, highlighting the study’s realism and applicability.

A primary limitation of this study is its small sample size, which restricts the statistical power of the quantitative findings and limits the generalizability of results to broader athletic populations. The relatively short duration of the intervention also constrains the ability to observe long-term performance or health effects. In addition, the study relied heavily on self-reported dietary adherence, which introduces the likelihood of recall bias and social desirability bias, potentially affecting the accuracy of reported compliance. Micronutrient status was not reassessed post-intervention, so the effect of supplementation on biochemical outcomes could not be evaluated. Lastly, individual variability in metabolism, training load, and external stressors was beyond the scope of this study, but these factors may have influenced outcomes and warrant further investigation in future research.

Future studies should consider extending the duration of interventions and recruiting larger, more diverse cohorts of athletes across different sporting disciplines to better assess the long-term sustainability and impact of personalized nutrition on performance. Incorporating more objective measures of dietary adherence, such as biomarkers or wearable technology, could also provide a more accurate assessment of compliance. In addition, longer-duration studies should integrate objective pre- and post-intervention performance assessments (e.g., strength, power, and endurance tests such as countermovement jump, 1RM, or sprint times measured using equipment or timing systems). The inclusion of validated well-being, sleep, or fatigue scales could further strengthen the evaluation of performance improvements and athlete recovery. Moreover, future research may also explore the influence of external factors, such as training load and psychological stress, on the effectiveness of nutrition interventions, thereby providing a more holistic understanding of how personalized nutrition contributes to athlete health and performance.

Conclusions

All respondents emphasized the importance of culturally tailored, personalized nutrition interventions in enhancing competitive outcomes. While athletes reported subjective improvements in how they felt, the study did not formally measure well-being or recovery outcomes. Future research involving larger cohorts and extended follow-up, using both quantitative and qualitative approaches, is recommended to strengthen the evidence base and refine protocols for the safe and effective implementation of personalized interventions across diverse athletic populations.

Abbreviations

1RM

One repetition maximum

CG

Control group

EVOO

Extra virgin olive oil

g/kg

Grams per kilogram

IG

Intervention group

IOC

International olympic committee

IU

International units

ORS

Oral rehydration solution

PB

Personal best

RCT

Randomized controlled trial

SB

Seasonal best

SNK

Sports nutrition knowledge

SNKQ

Sports nutrition knowledge questionnaire

USG

Urine specific gravity

Authors’ contributions

RJ conceived and designed the study. RJ and KW involved in data collection. RJ and KW contributed to drafting the manuscript. IN, NSK, TM, and APH, as supervisory team members participated in the revision of the paper. Additionally, all authors carefully reviewed and approved the final version of the manuscript.

Funding

No funding was received for conducting this study.

Data availability

The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

Written informed consent was obtained from all participants prior to their inclusion in the study, and they were given the option to withdraw from the study or continue follow-up without any impact on their clinical management, in accordance with the Helsinki Declaration. Ethical approval was granted by the Institutional Ethical Review Committee at the Faculty of Medicine, University of Peradeniya, Sri Lanka (2023/EC/71). This trial is registered with the Sri Lanka Clinical Trials Registry (2024/013), with a Universal Trial Number (UTN): U1111-1304-8890.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.