Enhancing physical fitness in older adults: a six-month medium intensity training intervention yields significant improvements

Abstract

Background

Maintaining physical fitness in older adults is crucial for preventing functional decline. This study aimed to examine the effects of a 6-month medium-intensity training (MIT) programme on physical fitness components in older adults.

Methods

In this randomized controlled trial, 72 older adults aged 60–70 years in Indonesia were randomly assigned to either an exercise group (EG; n = 36) or a control group (CG; n = 36). The EG participated in MIT sessions (60 minutes, 3 times per week). Each session consisted of a warm-up with joint mobility and flexibility exercises, followed by 15–20 minutes of moderate-intensity walking performed at 55-70% of maximum heart rate, a strength training phase targeting major muscle groups with 8–10 repetitions per movement using bodyweight or light resistance, and a cooldown phase incorporating stretching for major muscle groups. Physical fitness was assessed using the Senior Fitness Test at baseline and post-intervention. Group × time interaction effects were analyzed using repeated measures ANOVA. Effect sizes were calculated using partial eta squared (partial η²), with 95% confidence intervals (CI) reported.

Results

Significant group × time interaction effects were observed for lower-limb strength (post-intervention: EG = 13.40 ± 3.22 vs. CG = 10.55 ± 2.20 reps; partial η² = 0.167, 95% CI [0.041, 0.296], p = 0.02, upper-body strength (15.55 ± 2.88 vs. 11.37 ± 1.71 reps; partial η² = 0.223, 95% CI [0.085, 0.352], p= 0.00), lower-body flexibility (3.69 ± 2.93 vs. 2.50 ± 4.04 cm; partial η² = 0.101, 95% CI [0.013, 0.229], p= 0.01), and aerobic endurance (468.26 ± 88.49 vs. 417.50 ± 33.72 m; partial η² = 0.325, 95% CI [0.172, 0.460], p< 0.001). No significant interactions were found for upper-body flexibility or agility (p>0.05). All values in parentheses represent post-intervention means ± standard deviations.

Conclusions

A structured 6-month MIT programme significantly improved key physical fitness domains in older adults, particularly muscular strength and aerobic capacity. These findings underscore the importance of implementing regular, moderate-intensity exercise as a practical strategy to support healthy aging and reduce functional limitations.

Trial registration

The trial was registered at Thai Clinical Trials Registry no TCTR20250407006 (date of registration on April 7, 2025).

Supplementary Information

The online version contains supplementary material available at 10.1186/s13102-025-01401-1.

Background

The global increase in the population of older adults poses a unique challenge to healthcare systems, as aging is often accompanied by declines in physical fitness, muscle strength, and functional independence. In recent years, there has been growing recognition of the importance of physical fitness in older populations to mitigate the risks associated with aging, including chronic diseases, loss of mobility, and dependency in performing activities of daily living (ADL) [1]. Lack of physical activity is a global issue for adults that can lead to sedentary behaviour and a higher prevalence of health complications and chronic diseases [2]. Regular physical activity has been shown to yield substantial benefits for older adults, such as improved cardiovascular health, enhanced muscular strength, and overall better quality of life. However, as physical capabilities tend to decrease with age, finding sustainable and safe approaches to exercise is crucial for this demographic [3]. Physical inactivity remains a significant risk factor for older adults, contributing to a range of health issues, including obesity, cardiovascular disease, and frailty. As older adults are more likely to lead sedentary lifestyles due to age-related physical limitations, addressing this issue with appropriately structured exercise programs is crucial [4]. The health benefits of regular physical activity in aging populations are clear; even moderate physical activity has been shown to reduce the risk of premature mortality and delay the onset of debilitating diseases [5]. However, despite these benefits, many older adults face barriers to exercise, including concerns about safety, physical limitations, and a lack of guidance on appropriate levels of intensity [6]. Research focusing on medium-intensity training interventions for older adults provides valuable insights into how moderate exercise programs can be feasibly implemented to improve physical health [7]. Medium-intensity training (MIT), which encompasses activities like brisk walking, moderate cycling, and low-impact aerobic exercises, is widely recognized as a suitable and effective exercise intensity for older adults. MIT is beneficial as it can be maintained over time and avoids some of the challenges associated with high-intensity workouts. For instance, evidence suggests that older men may require longer than three days to recover from a single bout of high-intensity interval training (HIIT), indicating that care should be taken when prescribing HIIT regimens to older individuals due to the prolonged recovery demands and potential risks if not appropriately supervised [8]. Nonetheless, recent evidence also highlights that HIIT can be safe and feasible for older people [9]. HIIT interventions in older adults may be effective at promoting improvements in functional movement, though it is unclear whether HIIT is superior to MIT [10]. Therefore, rather than dismissing HIIT outright, this study emphasizes MIT as a more accessible and sustainable alternative for broad community application particularly where supervision and equipment are limited. In the present study, the MIT program also integrated strength and flexibility exercises to comprehensively support the functional needs of older adults. Resistance exercise is highly effective in improving lower body strength, enhancing muscle function, balance, and overall mobility [11]. Studies have shown that moderate-intensity resistance activities typically defined as exercises performed at 50–70% of one-repetition maximum (1-RM) or involving 8–12 repetitions per set are well-tolerated by older adults and can promote notable improvements in physical health markers, including cardiorespiratory fitness, muscle mass, and metabolic health [11–13]. A six-month intervention period, as suggested in recent research, offers sufficient duration for sustainable physical improvements [14]. Recent systematic reviews have highlighted that while supervised exercise programs often yield greater improvements in physical function among older adults, unsupervised home-based programs can still offer meaningful benefits, particularly in enhancing balance and promoting autonomy [15, 16]. However, the evidence remains limited and inconsistent, underscoring the need for further investigation into the feasibility and effectiveness of unsupervised exercise interventions in this population.

This study aims to investigate the effectiveness of a six month MIT in producing measurable enhancements in key health related physical fitness components namely muscular strength, flexibility, aerobic capacity, and agility among older adults. By examining the effects of MIT on physical fitness in older adults, this study seeks to provide evidence for practical, community-based exercise programs that do not require laboratory-grade equipment or continuous supervision, making them more applicable to real-world settings. The potential outcomes of this research are highly relevant to public health, as they emphasize a feasible way to enhance physical fitness in the aging population. Given that MIT has been shown to improve key health markers, such as cardiorespiratory endurance, muscle strength, and functional independence [17, 18], this study will assess whether a six-month intervention can yield significant improvements across these areas. In doing so, it hopes to demonstrate that MIT is not only a practical but an effective method for supporting healthy aging, reducing the healthcare burden associated with age-related conditions, and ultimately enhancing the quality of life for older adults.

Methods

Participants

The study involved a total of 72 participants, comprising 33 women and 39 men, aged between 60 and 70 years, from two distinct districts in South Sumatera, Indonesia. The research was carried out over a six-month period, from May to November 2022. The required sample size was calculated using G*Power software (version 3.1.9.7) for a repeated-measures ANOVA. Assuming a moderate effect size (f = 0.25), an alpha of 0.05, and a power of 0.80, the analysis indicated a minimum of 54 participants (27 per group) to detect between-group differences. To account for possible attrition during the intervention period, 72 participants were initially enrolled. Participants were randomly assigned to either the experimental group (EG; n = 36) or control group (CG; n = 36) using a computer-generated random sequence created by an independent researcher uninvolved in participant enrollment or outcome assessment. All participants completed the intervention period, and no dropouts were recorded, as shown in the participant flow diagram Fig. 1. Adherence to the program was high, with 100% of participants attending at least 85% of the prescribed training sessions, thereby meeting the predefined adherence criterion. Allocation concealment was ensured using sealed, opaque envelopes. However, stratified randomization by sex was not implemented due to logistical constraints during recruitment, which resulted in a slight gender imbalance between the groups. This limitation and its implications are addressed in the discussion section. The study complied with the ethical standards set forth in the Declaration of Helsinki and received approval from Wuhan Sports University (ID: WHSU 2022013). This study was registered in TCTR of clinical trials (TCTR20250407006, date of registration on april 7, 2025). The reporting of this randomized controlled trial followed the CONSORT guidelines.

Fig. 1.

Participants flow diagram

Participants were recruited through collaboration with local public health centers, village authorities, and elderly community groups, with study information disseminated via posters and flyers placed at community health posts (posyandu lansia), religious centers, and administrative offices. Community health volunteers assisted in informing potential participants, who then contacted the research team and were pre-screened based on the inclusion and exclusion criteria. Those meeting eligibility requirements were invited to an in person session at a local health center or community hall, where the objectives and methodologies of the study were thoroughly explained. Informed written consent was obtained from each participant, ensuring their full understanding and agreement to take part in the study prior to baseline assessments. Inclusion criteria for participation were as follows: (1) the ability to communicate effectively; (2) a willingness to engage in the intervention program upon providing informed consent; and (3) the ability to ambulate without external assistance. Conversely, exclusion criteria included: (1) self-reported chronic diseases or mental health conditions, such as severe cardiovascular or pulmonary diseases, musculoskeletal disorders, or major depressive episodes; (2) sensory impairments, including significant visual or auditory deficits; (3) any recent fractures or surgeries involving the hip or vertebrae within the past two months; and (4) an inability to walk independently for distances exceeding 10 m. By implementing these criteria, the study ensured the selection of participants who were physically capable of engaging in the exercise interventions while excluding those with medical or physical conditions that could affect the outcomes. Participants in the control group were instructed to maintain their usual daily routines and refrain from engaging in any new structured physical activities during the study period.

Assessments

The Senior Fitness Test (SFT) is a comprehensive assessment tool specifically designed to evaluate the physical function of adults aged 60 years and older, with a focus on those who are generally in good health [19]. The primary aim of the SFT is to assess key physical fitness components that directly relate to the functional abilities required for independence in daily living activities among older adults. Recognizing the distinct physical challenges that accompany aging, the SFT comprises six targeted tests, each designed to measure an essential aspect of physical fitness. These tests include the 30-second Chair Stand Test (CST) to assess lower body strength, the 30-second Arm Curl Test (ACT) to evaluate upper body strength, the Chair Sit-and-Reach Test (CSRT) for flexibility, the Back Scratch Test (BST) to measure upper body flexibility, the 8-Foot Up-and-Go Test (FUGT) to assess agility and dynamic balance, and the 6-Minute Walk Test (6MWT) to gauge cardiovascular endurance. Each of these six tests within the SFT provides reliable and relevant data on the different dimensions of physical fitness in older adults, making it a valuable instrument for research on aging and physical fitness interventions.

Training program

Participants followed a meticulously structured warm-up regimen designed to enhance joint mobility and prepare the body for physical activity. This warm-up included a variety of range of motion (ROM) exercises that specifically targeted key areas such as the shoulders, hips, knees, ankles, and chest, ensuring comprehensive engagement of both upper and lower body joints. In addition to these ROM exercises, participants performed specific stretches aimed at improving flexibility, including knee-to-chest movements, sit-and-reach exercises, and seated forward bends, all of which focused on enhancing the flexibility of the lower back and hamstrings [20, 21].

Following the warm-up phase, participants engaged in a 15–20-minute walking session at moderate intensity. The training intensity was prescribed as moderate, corresponding to 55–70% of the heart rate reserve (HRR), which is widely recommended for older adults [22]. To calculate HRR, the maximal heart rate (HRmax) was estimated using the Gellish formula (HRmax = 206.9–0.67 × age) [23], and the resting heart rate (HRrest) was measured individually. The target training heart rate was then derived using the Karvonen formula: Target HR = (HRmax – HRrest) × %intensity + HRrest [24]. Importantly, %HRmax values were not applied in prescribing training zones, they were only considered as general reference thresholds, while the actual training prescription and monitoring relied exclusively on %HRR to ensure individualized and physiologically accurate intensity control in older adults. Resting heart rate was measured individually by each participant in a seated position, using radial pulse palpation, as recommended for accuracy in resting conditions [25]. All target heart rate values were then calculated and verified by certified exercise specialists prior to the start of the intervention. During training, heart rate was monitored manually by palpating the radial or carotid artery for 15 s and multiplying by four to obtain beats per minute (bpm). This approach allowed individualized control over cardiovascular workload during the aerobic phase of the session.

The core of each training session involved a series of strength exercises, organized into four sets per exercise. These exercises were selected to target major muscle groups and included hip extensions to strengthen the lower body, leg curls to enhance hamstring strength, and wall push-ups to develop upper body endurance and stability, The exercises were performed at home without the use of specialized devices, relying on bodyweight movements and minimal equipment, such as resistance bands or dumbbell, as needed. The exercises followed a progressive structure, gradually increasing in intensity or volume to promote strength improvements over time. Exercise intensity was set at a moderate level, approximately 60–70% of estimated one-repetition maximum (1-RM), and was monitored using the Repetitions in Reserve (RIR) approach, aiming for 2–3 repetitions remaining at the end of each set. This corresponded to a perceived exertion level of 12–14 on the Borg scale. Each exercise was performed with 8–10 repetitions, with the entire strength training routine being conducted three times per week to ensure consistent improvements in muscular strength and endurance.

Although the training was home-based, it was partially supervised through a structured hybrid monitoring approach. At the start of the program, participants attended an in-person orientation session led by a certified exercise specialist, where all movements and safety protocols were demonstrated. Thereafter, participants received weekly follow-up through scheduled phone or video calls to assess progress, ensure correct technique, and adjust the training load based on the progression plan. To enhance adherence, participants were provided with illustrated training booklets and individualized exercise logs, which they were required to complete and submit weekly. Adherence was defined as completing at least 85% of prescribed sessions. Progression strategies were standardized and included gradual increases in repetitions, resistance, or time-under-tension every two weeks. The training followed a circuit-based structure, where each session consisted of a warm-up, aerobic phase, and strength component, with 30–60 s of rest between sets and exercises. Over the 6-month period, progression was implemented in three phases: (1) familiarization and adaptation (weeks 1–4), (2) development (weeks 5–12), and (3) consolidation and maintenance (weeks 13–24), with progressive variation in exercise selection, resistance levels, and weekly volume. A summary of the training structure, sample exercises, perceived exertion targets, rest intervals, and weekly volume is presented in Table 1. These strategies were designed to address known challenges in maintaining long-term adherence to home-based resistance training programs in older adults [26]. To conclude each session, participants engaged in a series of cooldown exercises focused on flexibility and muscle relaxation. This cooldown routine included hamstring stretches, standing calf stretches, seated back extensions, and hip stretches, aimed at improving the flexibility of key muscle groups. In addition, neck and shoulder stretches, along with chest stretches, were included to release tension [27, 28]. This combination of flexibility exercises facilitated the prevention of muscle stiffness, preparing the participants for subsequent sessions [29].

Table 1.

Overview of the 6-month home based medium intensity training

Phase	Weeks	Warm-Up (10–15 minutes)	Aerobic Training (15–20 minutes)	Strength Training (4 sets per exercise)	Cool Down (10 minutes)	Target Intensity	Rest Interval
Familiarization & Adaptation	1–4	Neck rolls Shoulder circles Arm swings Hip rotations Knee lifts Ankle circles Side bends Standing hamstring stretch (8–10 reps each)	Walking at moderate intensity (55–65% HRR) for 15–20 minutes, calculated by Karvonen formula (HRmax = 206.9 − [0.67 × Age]); heart rate monitored manually by palpating radial or carotid pulse	Wall push-ups Chair squats Seated hip abductions (8–10 reps per set; intensity ~60–65%, RIR 2–3)	Seated forward bend Calf stretches Shoulder rolls neck stretches wrist stretches (hold 20–30 seconds each)	Borg 12–13; RIR 2–3	30–60 seconds between sets
Development	5–12	Dynamic chest openers Cat-cow stretches Trunk rotations Side bends Knee hugs Arm crosses Hip circles Standing calf stretches (10 reps each)	Brisk walking or grapevine steps at 60–70% HRR for 15–20 minutes; heart rate monitored manually as above	Step-ups Resistance band rows Leg curls Bird-dog (8–10 reps per set; intensity ~65–70%, RIR 2–3)	Supine twists Seated back extensions quad stretches hip flexor stretches seated spinal twists ankle pumps Chest stretches (hold 20–30 seconds each)	Borg 13–14; RIR 2–3	30–60 seconds between sets
Consolidation & Maintenance	13–24	Marching in place Thoracic spine rotations Lunges with reach Arm raises (frontal and lateral) Side leg raises Ankle circles (10–12 reps each)	Continuous walking or low-impact aerobic circuit at 65–70% HRR for 15–20 minutes; heart rate monitored manually as above	Wall push-ups Dumbbell bicep curls Hip bridges Side leg raises (8–10 reps per set; intensity ~70%, RIR 1–2)	Neck stretches Overhead reaches Hip flexor stretches hamstring stretches seated calf stretches butterfly stretch chest opener against wall (hold 30 seconds each)	Borg 13–14; RIR 1–2	30–60 seconds between sets

Statistical analyses

All data are expressed as mean ± standard deviation (SD). Prior to inferential testing, the normality of the data distribution was assessed using the Kolmogorov–Smirnov test. A repeated measures two-way analysis of variance (ANOVA) was employed to examine group (exercise vs. control) × time (pre- vs. post-intervention) interaction effects on each component of physical fitness. Where significant interaction effects were detected, post hoc comparisons were conducted using Bonferroni-adjusted paired t-tests to determine within-group and between-group differences. Effect sizes were calculated using partial eta squared (ηp²), interpreted according to Cohen’s guidelines (small = 0.01, medium = 0.06, large = 0.14), and accompanied by 95% confidence intervals (CI) to provide estimates of precision. The significance level was set at p < 0.05 for all analyses. Statistical analyses were conducted using IBM SPSS Statistics for Windows, version 22.0 (IBM Corp., Armonk, NY, USA).

Results

Participant characteristics are presented in Table 2. Both groups were comparable in terms of age, gender distribution, employment, and health status, though the CG had a slightly higher proportion of participants with college-level education. A substantial number of participants in both groups reported chronic health conditions, particularly hypertension and diabetes. Baseline values showed no statistically significant differences between the EG and CG across all outcome variables (p > 0.05; see Tables 3 and 4), confirming the initial comparability between groups. A two-way repeated measures ANOVA revealed significant group × time interaction effects in several outcome measures. In the CST, a significant interaction was observed, F(1,38) = 7.62, p = 0.009, partial η² = 0.167, indicating greater gains in the EG (13.40 ± 3.22 reps) than in the CG (10.55 ± 2.20 reps) (Fig. 2A). The ACT also showed significant improvement in the EG (F(1,38) = 10.91, p = 0.002, partial η² = 0.223; EG: 15.55 ± 2.88 reps, CG: 11.37 ± 1.71 reps) (Fig. 2B). For flexibility, CSRT demonstrated a modest but significant interaction effect, F(1,38) = 4.27, p = 0.045, partial η² = 0.101, favoring the EG (3.69 ± 2.93 cm) over the CG (2.50 ± 4.04 cm) (Fig. 2C). In contrast, BST and FUGT did not show significant group × time interactions (p > 0.05), although within-group improvements were noted (Fig. 2D and E). The 6MWT, however, revealed a strong interaction effect, F(1,38) = 18.33, p < 0.001, partial η² = 0.325, with the EG achieving superior gains in aerobic endurance (468.26 ± 88.49 m) compared to the CG (417.50 ± 33.72 m) (Fig. 2F). All post hoc comparisons were Bonferroni-adjusted, and 95% confidence intervals were calculated for effect sizes to ensure statistical accuracy and interpretability.

Table 2.

Participant characteristics

		EG	CG
Sex
	Male	75.0%	33.3%
	Female	25.0%	66.7%
Age (years)
	60–65	80.6%	66.7%
	66–70	19.4%	33.3%
Work
	Work	13.9%	11.1%
	No Work	86.1%	88.9%
Education
	Elementary School Equivalent	5.6%	5.6%
	Junior High School Equivalent	11.1%	38.9%
	High School Equivalent	80.6%	19.4%
	College	2.8%	36.1%
Disease History
	High blood pressure	61.1%	50.0%
	Diabetes	41.7%	38.9%
	Knee pain	47.2%	30.6%
	Don’t know	8.3%	13.9%

Table 3.

SFT outcomes by gender and age group in EG

Variable		Male 60–65 (Mean ± SD)	Male 66–70 (Mean ± SD)	Female 60–65 (Mean ± SD)	Female 66–70 (Mean ± SD)	Total 60–65 (Mean ± SD)	Total 66–70 (Mean ± SD)
CST (reps)	Pre	11.3 ± 2.9	11.0 ± 2.2	11.7 ± 3.1	10.5 ± 2.8	11.5 ± 3.0	10.8 ± 2.5
	Post	13.8 ± 3.3	12.5 ± 3.0	13.4 ± 3.1	12.3 ± 3.0	13.7 ± 3.2	12.7 ± 3.0
ACT (reps)	Pre	14.5 ± 2.7	13.8 ± 2.6	13.8 ± 2.8	12.8 ± 2.5	14.3 ± 2.7	13.4 ± 2.5
	Post	16.1 ± 2.9	15.3 ± 3.0	15.5 ± 2.8	14.1 ± 3.2	15.9 ± 2.8	15.0 ± 3.0
CSRT (cm)	Pre	9.2 ± 4.1	8.5 ± 4.3	8.9 ± 4.5	9.1 ± 3.8	9.1 ± 4.1	9.0 ± 4.2
	Post	3.8 ± 3.0	3.6 ± 2.8	3.5 ± 2.9	3.5 ± 3.1	3.8 ± 2.8	3.5 ± 3.0
BST (cm)	Pre	−7.5 ± 4.2	−6.8 ± 4.0	−7.3 ± 4.0	−7.1 ± 4.1	−7.4 ± 4.2	−7.3 ± 3.9
	Post	−6.3 ± 4.3	−6.0 ± 4.0	−6.5 ± 4.2	−6.5 ± 4.8	−6.4 ± 4.1	−6.5 ± 4.5
FUGT (sec)	Pre	6.3 ± 1.2	6.2 ± 1.1	6.2 ± 1.1	6.3 ± 1.0	6.3 ± 1.2	6.2 ± 1.1
	Post	6.0 ± 1.1	6.0 ± 1.0	6.0 ± 1.0	6.0 ± 1.1	6.0 ± 1.1	6.0 ± 1.0
6MWT (m)	Pre	392 ± 80	388 ± 75	389 ± 75	401 ± 80	390 ± 80	395 ± 75
	Post	470 ± 90	465 ± 85	462 ± 85	470 ± 95	470 ± 85	465 ± 95

Table 4.

Outcomes by gender and age group in CG

Variable		Male 60–65 (Mean ± SD)	Male 66–70 (Mean ± SD)	Female 60–65 (Mean ± SD)	Female 66–70 (Mean ± SD)	Total 60–65 (Mean ± SD)	Total 66–70 (Mean ± SD)
CST (reps)	Pre	11.6 ± 2.8	11.3 ± 2.6	11.5 ± 2.6	11.4 ± 2.9	11.6 ± 2.7	11.4 ± 2.9
	Post	10.8 ± 2.3	10.5 ± 2.1	10.4 ± 2.1	10.3 ± 2.0	10.7 ± 2.2	10.4 ± 2.1
ACT (reps)	Pre	13.3 ± 2.5	12.8 ± 2.5	12.7 ± 2.4	12.9 ± 2.8	13.0 ± 2.5	12.5 ± 2.6
	Post	11.7 ± 1.8	11.1 ± 1.4	11.2 ± 1.6	11.4 ± 1.6	11.4 ± 1.7	11.2 ± 1.6
CSRT (cm)	Pre	12.3 ± 4.7	11.8 ± 4.8	11.9 ± 4.9	11.6 ± 5.1	12.2 ± 4.7	11.8 ± 5.0
	Post	2.6 ± 3.9	2.3 ± 4.0	2.4 ± 4.1	2.5 ± 4.5	2.5 ± 3.9	2.6 ± 4.1
BST (cm)	Pre	−6.8 ± 4.0	−7.0 ± 4.4	−6.9 ± 4.2	−6.7 ± 4.5	−6.7 ± 4.0	−6.9 ± 4.2
	Post	−6.1 ± 4.4	−6.0 ± 4.1	−6.2 ± 4.4	−6.1 ± 4.2	−6.1 ± 4.3	−6.1 ± 4.4
FUGT (sec)	Pre	6.7 ± 1.3	6.8 ± 1.2	6.8 ± 1.2	6.7 ± 1.4	6.7 ± 1.3	6.7 ± 1.3
	Post	6.4 ± 1.2	6.3 ± 1.3	6.3 ± 1.1	6.3 ± 1.2	6.4 ± 1.2	6.3 ± 1.2
6MWT (m)	Pre	422 ± 70	418 ± 72	423 ± 71	415 ± 73	422 ± 70	421 ± 75
	Post	420 ± 34	416 ± 36	415 ± 32	413 ± 35	420 ± 33	415 ± 32

Fig. 2.

Test outcomes pre and post training. EG = Exercise-group, CG = Control-group; Panel A shows chair stand test (CST) measured in repetitions, panel B shows arm curl test (ACT) measured in repetitions, panel C shows chair sit and reach test (CSRT) measured in cm, panel D shows back scratch test (BST) measured in cm, panel E shows 8 foot up and go test (FUGT) measured in second and panel F shows 6 minutes walking test (6 MWT) measured in meter

Discussion

The primary aim of this study was to evaluate the impact of a medium intensity training program on multiple domains of physical fitness in older adults, as assessed by the Senior Fitness Test. After a six-month intervention, results revealed statistically and practically meaningful improvements in select areas of physical fitness, specifically in lower- and upper-body muscular strength, where significant group × time interaction effects and moderate effect sizes were observed. These findings support the efficacy of MIT for improving aerobic capacity and muscular strength in aging populations, although improvements were not uniformly observed across all domains.

Strength related outcomes. Lower limb strength, evaluated through the CST, demonstrated a significant group × time interaction (F(1,38) = 7.62, p = 0.009, partial η² = 0.167), indicating a meaningful differential gain favoring the EG over the CG. The EG demonstrated an 18.5% improvement in CST performance, whereas the CG experienced an 8.6% decline. This corresponds to a meaningful between-group difference of approximately 27.1%. In physical health research involving older adults, changes of 5% or more are generally considered clinically meaningful [30], reflecting improvements that can enhance functional capacity and overall quality of life [31]. Thus, the substantial gains observed in the EG are not only statistically significant but also likely to have practical relevance in improving lower limb strength and mitigating mobility-related impairments. This finding demonstrates the effectiveness of various exercises for increasing lower limb strength, which is crucial for improving mobility, functional independence, and overall quality of life among older people [32–34]. Conversely, the decline seen in the CG may reflect typical age-related muscle function deterioration, underscoring the importance of exercise interventions to preserve or improve physical fitness. The significant improvement in the Chair Stand Test following the MIT in our study is consistent with findings from previous studies [35–37] and demonstrates how exercise can increase lower limb strength through various physiological mechanisms that lead to muscle growth, neuromuscular adaptation, and ultimately improvement in muscle function. The ACT was used to assess upper body strength, also showed a statistically significant group × time interaction (F(1,38) = 10.91, p = 0.002, partial η² = 0.223), with substantial post-intervention gains in the EG compared to the CG. This moderate effect size suggests that the MIT program elicited a physiologically meaningful improvement in upper-body strength. Previous work has shown that moderate-intensity training has a significant impact on upper body strength after 12 weeks [38]. This finding consistent with previous work showing how performing exercise three times a week over a three month period can increase upper body strength among the elderly [39]. Maintaining functional upper-body strength levels is important, especially in older persons, for maintaining physical function, preventing chronic diseases, and performing everyday activities. Many typical tasks rely greatly on upper body strength, such as hand grasping, lifting, and transferring [40, 41]. Therefore, maintaining upper body strength is crucial in preventing and delaying the onset of disability, frailty, and dependence as people age, while regular evaluation may support early detection of decline and guide appropriate interventions.

Flexibility related outcomes. The CSRT was used to asses lower body flexibility. Having a good range of motion and flexible muscles is necessary to achieve the normal range scores on the test. CSRT performance was improved in the EG compared with CG, which may be attributed to using the particular stretching exercises in the intervention, in addition to the warm-up and stretching completed before the test. In the CSRT, a statistically significant group × time interaction was observed (F(1,38) = 4.27, p = 0.045), but with a partial η² of 0.101, suggesting only a small practical effect. While the EG showed a ∆20% gain, this improvement should be interpreted cautiously given the effect size is on the threshold of what is considered meaningful. The BST, assessing upper body flexibility, did not yield a significant group × time interaction, and the effect size was < 0.1. Although the EG showed a ∆21% within-group increase, the absence of significant between-group differences limits the interpretability of this change. Taken together, these results suggest that six months of MIT resulted in a considerable increase in range of motion, demonstrating that MIT can improve overall mobility in older people, even if changes in upper body flexibility were not statistically significant. This finding is consistent with previous work [42–44] and demonstrates similar increases in the range of motion in lateral bends, standing leg raises, hip extensions, and hip internal rotations in 65-year-old patients following an unsupervised flexibility exercise program. Baranda et al. [45] found that a 12-week stretching intervention led to a 15.14° gain in passive hip flexion ROM, representing approximately a 21% improvement. Although medium intensity training appears to be a useful method for improving range of motion in multiple joints, it is hard to assess the gains in flexibility improvement elicited by either resistance exercise or flexibility exercises (with or without other supplemental training modalities) due to differences in subjects, training duration, intensity, and frequency, as well as variance in the subjects’ initial fitness status. Furthermore, if older adults engage in training over an extended period, the range of motion in relevant joints may continue to improve, as shown in previous studies [46]. This research finding consistent with [47] which showed that resistance training can significantly improve flexibility when exercises are performed through the full range of motion and both agonist and antagonist muscle groups are activated. During aging, flexibility becomes increasingly important, as reduced flexibility has been linked to neuromuscular stiffness and hip joint contracture that may contribute to musculoskeletal disorders [48] and is independently associated with metabolic syndrome an established risk factor for functional decline and disability in older adults [49].

Similar research findings show how resistance exercise improved flexibility in both younger and older individuals [50]. Furthermore, regular mobilization has been seen to explain greater upper body flexibility, implying that resistance training through the whole range of motion can increase flexibility. Agility, measured via the FUGT, also did not present a significant group × time interaction (p > 0.05), and the associated effect size was below the threshold for practical relevance. Although the EG demonstrated a ∆9.4% within-group improvement, these changes should not be over-interpreted as evidence of superiority of the MIT intervention.

An improvement in agility is consistent with previous work [51]. When it comes to executing a wide range of typical mobility tasks, agility is essential. These include moving quickly to avoid dangerous objects, walking, climbing stairs, using the restroom, boarding and alighting from private and public transportation, crossing the street, and answering the door or phone. While few investigations have examined the relationship between age and measures of agility, studies using targeted agility assessments have demonstrated a clear decline with aging: MacKenzie et al. found that older age was associated with significantly reduced hop distance and increased hop length variability both valid markers of agility decline due to neuromuscular aging [52]. A cross-sectional comparison also revealed that older adults living in retirement facilities performed agility tasks (e.g., TUG, lateral stepping velocity) up to 20% slower than community-dwelling older adults, further supporting age-related decline in agility [53]. Results indicate that including particular balance and coordination exercises in older people exercise programs in addition to strength, flexibility, and aerobic activities is the best way to increase agility and lower the risk of falling [54, 55]. Based on previous research, the 8-foot up and go test may distinguish between different functional categories in older adults and can adapt to changes brought on by higher physical activity levels. However, in the absence of statistically significant interaction effects, our findings suggest that the MIT program alone may not be sufficient to enhance agility beyond natural variation or test familiarity.

The 6MWT was used to assess aerobic capacity, showed a significant group × time interaction (F(1,38) = 18.33, p < 0.001), with an effect size of partial η² = 0.325, indicating a strong practical effect. The EG increased their average walking distance from 392 m to 468 m, while the CG showed minimal change. The increases in aerobic capacity discovered in this study are comparable with the findings of Tan et al. [56] who discovered an increase in 6 min walk distance after a 6-month intervention exercise program. These findings are consistent with previous research by Machado et al. [57] who demonstrated that a six-month program combining aerobic and resistance exercises led to significant improvements in 6MWT performance, including greater walking speed and distance. Participants in the intervention group exhibited enhanced claudication tolerance and physical function, highlighting the effectiveness of moderate-intensity multimodal training in improving ambulatory capacity in older adults. These results align with previous reports [58], which showed that moderate intensity resistance training, when performed alone or in conjunction with aerobic exercise, led to an increase in 6MWT distance of approximately 15–17% after 2–6 months. Furthermore, Renaud et al. [59] indicated that following three months of aerobic exercise training in older adults, 6MWT distance increased considerably by 9% and Gudlaugsson et al. [60] proved that after six months of exercise training, older people were associated with an increase of the 6MWT distance by 14%. Aerobic capacity declines occur throughout life, accelerating much faster in later years, appearing to be declining at a rate of 5 to 15% every decade [61–63]. Medium intensity training stimulates adaptations in the cardiovascular system, including increased stroke volume (the amount of blood pumped by the heart with each beat), cardiac output (the volume of blood pumped by the heart per minute), and efficiency of oxygen delivery to the muscles [64, 65]. These adaptations result in improved circulation, allowing more oxygen-rich blood to be delivered to working muscles during exercise. Consistently undertaking medium intensity training leads to a cascade of physiological adaptations that collectively improve aerobic capacity, allowing older people to perform physical activity with greater efficiency and endurance over time.

Taken together, the MIT program appears to confer domain-specific benefits, with the largest effect observed in aerobic capacity (partial η² = 0.325), followed by upper-body strength (partial η² = 0.223) and lower-limb strength (partial η² = 0.167). These findings indicate robust improvements across multiple physical domains, supporting the effectiveness of the intervention in enhancing both cardiovascular endurance and muscular strength among older adults. Changes in flexibility and agility, while showing within-group trends, were associated with small or trivial between-group effect sizes (η² < 0.1), limiting the confidence with which such changes can be described as meaningful “improvements.” These findings suggest that MIT is most efficacious in targeting aerobic capacity and muscular strength domains in older adults. Accordingly, any characterization of “clear benefits” should be restricted to those outcome areas where statistically significant and non-trivial effects were demonstrated. This study has certain limitations. The modest sample size and single-site recruitment may limit external validity. Manual heart rate monitoring may have introduced measurement variability, and neither dietary intake nor physical activity outside the intervention were controlled. Moreover, stratified randomization by sex was not feasible due to logistical constraints, leading to a minor gender imbalance. Despite these constraints, the study’s findings are directly applicable to community health settings, particularly in low-income populations. The intervention is low-cost, requires minimal equipment, and can be feasibly implemented in non-clinical environments. Future research should employ larger, multi-center trials with objective monitoring and longer follow-up periods to evaluate the program’s scalability and long-term effects.

Conclusions

In conclusion, this research demonstrates that a six-month medium-intensity training (MIT) intervention can significantly enhance physical performance in older adults, particularly in specific domains such as lower limb strength, upper body strength, and aerobic capacity. These improvements were supported by statistically significant group × time interaction effects and moderate to large effect sizes provide strong empirical support for the outcomes. While within-group improvements were observed in flexibility and agility, the between-group effect sizes in these domains were small or trivial (η² < 0.1), and in some cases below the threshold for moderate effects (η² ≤ 0.06). Therefore, these changes should be interpreted with caution, as their statistical and practical significance appears limited. However, even modest gains in flexibility and agility may hold clinical relevance for older adults, given their potential to support functional independence and reduce fall risk. These findings suggest that MIT is most beneficial for improving strength and endurance, while its effects on flexibility and agility may require additional or complementary interventions. These results highlight the transformative potential of sustained, moderate physical activity tailored to the abilities and needs of older adults. By targeting core components of physical fitness, particularly those with demonstrated statistical and practical significance, MIT contributes meaningfully to overall mobility, functional independence, and the reduction of age-related physical decline. In summary, these findings advocate for the promotion of medium-intensity training programs within community, clinical, and rehabilitation settings, as they offer an effective and sustainable approach to enhancing key aspects of physical fitness in older adults. Future research may expand on these findings by exploring different exercise modalities, durations, and intensities to further refine exercise recommendations. Encouragingly, the outcomes of this study support MIT as a practical and essential component of a healthy lifestyle, emphasizing its role in promoting autonomy and a higher quality of life in later years.

Abbreviations

ACT

Arm curl test

ADL

Activities of daily living

BPM

Beats per minutes

BST

Back scratch test

CST

Chair sit test

CSRT

Chair sit and reach test

FUGT

Foot-up and go test

HIIT

High intensity interval training

HRM

Heart rate maximum

HRR

Heart rate reserve

MICT

Moderate-intensity continuous training

MIT

Medium intensity training

1RM

1 Repetition maximum

6MWT

6 Minute walking test

Authors’ contributions

R.H. wrote the main manuscript text, designed the study, collected data and prepared tables, D.L. and W.L. methodology and supervision, S.G. review, editing, and supervision. All authors have read and agreed to the publish version of manuscript.

Funding

This research received no external funding.

Data availability

The required data and information can be obtained by contacting the corresponding author for the article (rahmamatt@gmail.com).

Declarations

Ethics approval and consent to participate

All experimental procedures followed the principles of the Helsinki Declaration and were approved by Wuhan Sports University (ID: WHSU 2022013). This research study followed the guidelines set by CONSORT for randomized controlled trials and was duly registered in TCTR of Clinical Trials (TCTR20250407006). All participants provided their written informed consent before the study started.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.