Biomechanics of backstroke start in elite swimmers: examining the relationship between posture, dynamic balance, and vertical jump performance

Abstract

This study aimed to investigate the relationship between the kinematic parameters of swimmers’ backstroke start performance and their dynamic balance, vertical jump, and postural characteristics. Seven elite male (n = 9) backstroke swimmers (FINA score: 711 ± 22.51) participated in the study, which consisted of four sessions. In the first session, swimmers performed two trials to familiarize themselves with the starting platform. In the second session, backstroke start kinematics were recorded using a stabilized GoPro10 Cam System and a DACTRONICS HS-200 Starting System, and analyzed using Kinovea 0.9.5 software. In the third session, dynamic balance (DB) was measured with the TecnoBody PK200 device, and vertical jump (VJ) performance was assessed with the Microgate Witty Wireless Timer. In the fourth session, posture was evaluated using the Apecs Posture Analysis Pro Plus 8.2.6 and the New York Posture Assessment (NYPA) method. Pearson correlation analysis revealed significant associations between PT-Anterior and HIPA (r = 0.667, p = 0.035), PT-Posterior and V (r = 0.703, p = 0.023), NYPA and WEH (r = − 0.663, p = 0.037), and PL-DB and WEH (r = − 0.721, p = 0.019). However, none of these associations remained statistically significant after the Benjamini–Hochberg false discovery rate (FDR) correction. In addition, no significant associations were observed between VJ performance and any of the kinematic parameters either before or after FDR correction. In conclusion, although potential associations were observed between postural characteristics, dynamic balance, and specific components of backstroke start kinematics, these associations were not confirmed following correction for multiple comparisons. Therefore, the findings should be interpreted as exploratory in nature.

Introductıon

The start is considered one of the key determinants of performance in swimming competitions and is recognized as a specific technical skill that encompasses the efficiency of movement both prior to the swimmer’s first contact with the water and at the moment of water entry; [40, 43]). It is evident that start performance plays a critical role in competitive swimming, particularly in sprint events where race outcomes are frequently determined by hundredths of a second [17].

Backstroke, unlike the other swimming strokes, is the only style that starts from within the water, giving it a unique starting structure. This distinctive feature makes the backstroke start technically more complex and complicates the understanding of the associated movement patterns and performance determinants [5, 37]. Previous studies have reported that the start phase in sprint swimming events may contribute up to approximately 30% of total race time, whereas more recent findings indicate that this proportion is around 26%. Nevertheless, despite these differences, the 15-m start phase remains a critical determinant of overall race performance [7, 13, 29].

The backstroke start is a complex process comprising six basic stages, from the preparatory position to surfacing: preparatory position, push-off from the wall, flight, water entry, underwater dolphin kick, and breakout to the surface (Maglischo 1993). Factors influencing backstroke start performance include not only technical proficiency but also various physical, kinematic, and biomechanical parameters, as well as rule changes and structural modifications to the starting platform [25]. Effective optimization of these factors enables swimmers to enter the water as quickly and efficiently as possible, thereby gaining a significant performance advantage at the beginning of the race [7].

However, the relationship between backstroke start performance and physical components such as dynamic balance, lower-extremity explosive force, and postural characteristics has been investigated only to a limited extent in the literature [25]. Previous studies have primarily focused on the temporal and kinematic parameters of start performance [22, 43–45], whereas the effects of physical and postural characteristics during the flight and water entry phases have not been sufficiently examined. It has been reported that body alignment, trunk control, and force transmission during the flight and water entry phases may influence start performance [6, 22]. Therefore, a more comprehensive evaluation of the multidimensional structure of backstroke start performance, including biomechanical, motoric, and postural components, is warranted.

Swimming is, by its nature, a sport performed in the horizontal plane and involves diagonal movement patterns. Repetitive diagonal movements in the horizontal plane may lead to postural adaptations over time [11]. On the other hand, swimming is frequently described in the literature as a fundamental sport for the development of physical fitness and the promotion of symmetrical muscular development [1, 10]. When these two perspectives are considered together, swimming may have a bidirectional effect, both contributing to postural improvement and potentially facilitating postural alterations due to repetitive loading. In particular, the high training volume in freestyle swimming may result in load-related adaptations and potential postural deviations in the spinal and lower extremity segments [35, 50, 51]. Therefore, the present study aimed to examine the relationship between pelvic tilt variables and backstroke start performance in swimmers. Pelvic alignment is considered to have significant biomechanical effects on lumbopelvic stability, force transmission, and the lower extremity kinetic chain. In particular, the lumbopelvic region has been reported to play a critical role in trunk stabilization, hip positioning, and horizontal force production required during swimming start performance [14, 42]. Lower-extremity explosive power is considered an important physical component of swimming start performance. The start phase requires the rapid generation and effective application of force, and both the magnitude and rate of force production directly influence the swimmer’s propulsion away from the wall or starting block [48]. Previous studies have demonstrated that lower-extremity strength and power characteristics are associated with swimming start performance, particularly with 5 m, 10 m, and 15 m performance outcomes [18, 48]. The vertical jump test is one of the most widely used valid and reliable field-based assessments of lower-extremity explosive power [31]. Furthermore, vertical jump performance has been reported to be associated with swimming start performance in competitive swimmers [18]. Most previous investigations have focused on track and grab start techniques performed from the starting block, examining the relationship between lower-extremity strength and power characteristics and start performance [42, 48].

Balance is a multidimensional motor skill closely related to posture, based on the integration of visual, vestibular, and somatosensory systems and the coordinated functioning of lower extremity muscle strength [46]. In the context of swimming, and particularly backstroke start performance, maintaining stability in the starting position and controlling dynamic balance play a critical role in effective force transfer during push-off and in the mechanics of water entry. Recent studies have also shown that balance control during both underwater and start phases is associated with start performance and various kinematic variables [2, 33].

The aim of the present study is to examine the relationships between kinematic variables associated with backstroke start performance and dynamic balance, vertical jump, and postural characteristics. The investigation of these relationships stems from the limited literature suggesting that backstroke start performance may be associated not only with technical and kinematic parameters but also with physical components and postural characteristics. Current studies have predominantly focused on the temporal and kinematic aspects of the start, whereas the relationships with physical performance indicators and postural variables have not been sufficiently addressed. The findings are expected to contribute to a more comprehensive evaluation of backstroke start performance, potentially supporting the improvement of start efficiency and indirectly contributing to enhanced sprint performance.

Hypothesis

H1a

There is a significant association between backstroke start performance kinematic parameters (time on-block, flight time, flight distance, total time, hip height, hand angle, hip angle, velocity, horizontal velocity, and vertical velocity) and pelvic tilt (anterior, posterior, lateral position) angle.

H0a

There is no significant association between backstroke start performance kinematic parameters (time on-block, flight time, flight distance, total time, hip height, hand angle, hip angle, velocity, horizontal velocity, and vertical velocity) and pelvic tilt (anterior, posterior, lateral position) angle.

H1b

There is a significant association between backstroke start performance kinematic parameters (time on-block, flight time, flight distance, total time, hip height, hand angle, hip angle, velocity, horizontal velocity, and vertical velocity) and dynamic balance (AP-DB, ML-DB, PL-DB) performance.

H0b

There is no significant association between backstroke start performance kinematic parameters (time on-block, flight time, flight distance, total time, hip height, hand angle, hip angle, velocity, horizontal velocity, and vertical velocity) and dynamic balance (AP-DB, ML-DB, PL-DB) performance.

H1c

There is a significant association between backstroke start performance kinematic parameters (time on-block, flight time, flight distance, total time, hip height, hand angle, hip angle, velocity, horizontal velocity, and vertical velocity) and vertical jump performance.

H0c

There is no significant association between backstroke start performance kinematic parameters (time on-block, flight time, flight distance, total time, hip height, hand angle, hip angle, velocity, horizontal velocity, and vertical velocity) and vertical jump performance.

H1d

There is a significant association between backstroke start performance kinematic parameters (time on-block, flight time, flight distance, total time, hip height, hand angle, hip angle, velocity, horizontal velocity, and vertical velocity) and NYPA total scores.

H0d

There is no significant association between backstroke start performance kinematic parameters (time on-block, flight time, flight distance, total time, hip height, hand angle, hip angle, velocity, horizontal velocity, and vertical velocity) and NYPA total scores.

Method

Participant

This study involved (n = 9) elite male backstroke swimmers from Turkey with experience in national and international competitions. The participants’ mean age was 17.02 ± 1.81 years, mean height was 181.5 ± 8.7 cm, mean body mass was 72.01 ± 8.56 kg, and mean FINA score was 711 ± 22.51 (Table 1). None of the participants had experienced any orthopedic injuries or musculoskeletal problems in the six months preceding the study. The research protocol received ethical approval from the Health Sciences Ethics Committee of Manisa Celal Bayar University (approval number: 20.478.486). Prior to enrollment, all athletes were informed both verbally and in writing about the purpose, procedures, and potential risks of the study, and written informed consent was obtained from each participant. All procedures were conducted in accordance with the principles of the Declaration of Helsinki. This study received no financial support.

Table 1.

Description of the kinematic parameters analyzed during the backstroke start

Parameter	Description
Time on-block (s)	Time elapsed from the start signal to the moment the swimmer leaves the block [41].
Flight time (s)	Time from block departure to the moment the hand contacts the water surface [41].
Flight distance (cm)	Horizontal distance covered from the block departure to the water entry of the hand [38].
Total time (s)	Total duration from movement initiation to the moment the hand touches the water [25].
Hip height (cm)	Vertical distance between the hips and the water surface during the preparatory position [41].
Hand angle (°)	Entry angle of the hand at the moment of water contact [43–45].
Hip angle (°)	Flexion angle of the hip at the moment the feet leave the block [21].
Velocity (m/sn)	Velocity from the start signal to hand entry into the water [16].
Horizontal Velocity (Vₓ)	Velocity component in the horizontal plane from the start signal to water entry [16].
Vertical Velocity (Vᵧ)	Velocity component in the vertical plane from the start signal to water entry [16].

Experiment protocol

The experiment was conducted in a 50-m Olympic swimming pool (depth: 3 m; water temperature: 27 °C). All participants performed their backstroke starts using a backstroke start platform (BSL; Omega OBL2PRO, Swiss Timing, Corgémont, Switzerland). While the platform height and handrail positions were left to individual preference, all participants opted for the highest platform setting, positioned 40 mm above the water surface, and the handrails in their highest horizontal position.

The study comprised four sessions. During the first session, two preliminary trials were conducted to allow participants to adapt to the start platform. Data obtained from these trials were used to optimize the positioning and calibration of the measurement systems. The GoPro10 camera system (Hypersmooth stabilization mode, 1080p resolution, 60 fps frame rate, linear lens angle, and automatic ISO) was positioned (Fig. 1) 0,75 m above the water surface, 3 m from the pool edge, and 5 m from the start device [19]. The “DAKTRONICS HS-200” start system was installed at a height of 1,80 m [12, 15, 47]. Figure 1 Experimental setup used for the assessment of backstroke start performance. a Measurements were conducted in a 50-m indoor Olympic swimming pool. The tripod and camera were positioned close to lane 1. b Detailed positioning of the camera and start system used to record the swimmer’s start performance. The camera was placed 0.75 m above the water surface, 3 m from the pool edge, and 5 m from the start system. c The start system used to initiate and record the swimmer’s starting performance, positioned 1.80 m above the ground. During the second session, swimmers performed three backstroke starts using the backstroke starting platform. Data on the swimmers’ backstroke start performance were analyzed using the motion analysis software Kinovea 0.9.5 [24, 28]. For performance analysis, the software was calibrated based on the width of the starting block (74 cm). Reference markers were used to increase measurement precision, and the trial in which each swimmer achieved the highest velocity (m/sn) was included in the analysis in order to minimize the effects of technical errors or submaximal attempts and to better reflect maximal competitive performance [8, 41]. Ten kinematic parameters related to the performance of the hands-off, take-off, and flight phases were assessed in the study [25]. To ensure consistency in the measurement procedure, all kinematic analyses were performed by the same analyst.

Fig. 1.

Biomechanical output measurement layout plan and related equipment location diagram

Table 1 presents descriptive information on the kinematic parameters examined in the study on backstroke start performance. A total of 10 kinematic parameters covering the hands-off, take-off, and flight phases were analyzed.

During the third session, athletes’ dynamic balance (DB) performance was assessed using the TecnoBody PK200 device. Measurements were conducted with the athletes standing barefoot on designated reference points. To ensure that participants could follow the instructions provided by the device, the screen was positioned at eye level [27]. Arm-swing vertical jump (VJ) performance was evaluated using the Microgate Witty Wireless Training Timer [26].

During the fourth session, postural analyses of the athletes were conducted in two separate sections. In the first section, static postural assessments were performed in the anterior, posterior, and lateral views using the Apecs-AI Posture Assessment and Correction System® (Apecs Posture Analysis Pro Plus, Version 8.6). To ensure measurement standardization and enable the clear identification of anatomical landmarks on the images, all assessments were conducted with participants wearing swimsuits, barefoot, and standing in the anatomical position. For the postural analyses, the camera system was stabilized using a tripod. Recordings were obtained in 4K resolution under fixed-distance and fixed-angle conditions to ensure measurement standardization. High-resolution images were acquired to enhance the visibility of anatomical landmarks, thereby maximizing visual accuracy during postural analyses. This approach aimed to facilitate more reliable identification of landmark points and minimize measurement errors [3]. In photogrammetry-based postural assessment applications, the reliability of pelvic tilt measurements has been reported to range from moderate to good (ICC = 0.642–0.842) [52].

In the second part of the postural assessment, the New York Posture Assessment (NYPA) method was applied to evaluate postural deviations across thirteen (13) distinct body regions. Each body region was assessed and scored according to the NYPA criteria, where a score of 1 indicated severe postural impairment, 3 indicated moderate postural impairment, and 5 represented normal postural alignment. The scores obtained from all regions were summed to calculate the total NYPA score used in the statistical analyses. Total scores ranged from 13 to 65, with lower scores indicating poorer posture and higher scores reflecting healthier postural alignment [24, 30].

Statistical analysis

Within the scope of the statistical analyses, data were expressed as minimum, maximum, mean, and standard deviation (SD) values. To evaluate the distribution characteristics of the dataset, skewness and kurtosis coefficients were examined, and the Shapiro–Wilk test was applied to statistically assess normality. Skewness and kurtosis values within the range of ± 1.5 [48, 49], together with non-significant Shapiro–Wilk test results (p > 0.05), indicated that the data met the assumption of normal distribution. Accordingly, parametric methods were preferred for the analyses. Pearson correlation analysis was used to determine the relationships between variables (* p < 0.05, ** p < 0.01, *** p < 0.001). To control the probability of false-positive results arising from multiple comparisons, the Benjamini–Hochberg False Discovery Rate (FDR) correction was applied. Statistical significance was accepted at p < 0.05. All analyses were performed using SPSS version 19.0 (SPSS Inc., Chicago, IL, USA).

Sample size analysis was conducted using G*Power 3.1 software. In the a priori power analysis performed for the correlation analysis, the effect size was set at 0.68, the alpha error probability at 0.05, and the statistical power (1 − β) at 0.80. The analysis indicated that the minimum required sample size for the study was 9 athletes [32].

Findings

Descriptive statistics for all study variables are presented in Table 2. Means, standard deviations, minimum values, and maximum values were calculated for participants’ anthropometric characteristics and the kinematic parameters of backstroke start performance. Pearson correlation analyses were conducted to examine the relationships between the kinematic parameters of backstroke start performance and VJ, PT, NYPA, and DB variables. The results of these analyses are presented in the text. Following Benjamini–Hochberg False Discovery Rate (FDR) correction, none of the observed correlations remained statistically significant (all padj ≥ 0.692). The overall correlation structure among the study variables is illustrated in Fig. 2.

Table 2.

Demographic information of swimmers and descriptive information on kinematic parameters of swimmers’ backstroke start performance

	Mean(x̄)	SD	Minimum	Maximum
Age (year)	17,02	1,81	17	21
Training Age (year)	8,13	0,55	7	10
FINA Score	711	22,51	670	750
Body Weight (kg)	72,1	8,56	63	89
Height (cm)	181,5	8,7	173	195
BMI (kg/m2)	21,8	1,32	20	24
Upper Extremity (cm)	84,5	7,14	71	96
Hand (cm)	20,2	0,79	19	22
Arm Span (cm)	188,2	10,91	178	209
Lower Extremity (cm)	102,75	7,32	94	116
Foot (cm)	26,4	2,17	22	29
Limb (cm)	51,8	17,53	43	101
Time on-block (s)	0,67	0,05	0,6	0,75
Hip height (cm)	46,76	10,87	25,03	62,68
Flight time (s)	0,15	0,06	0,03	0,23
Flight distance (cm)	244,53	20,42	219,77	283,55
Hand angle (°)	31,61	6,86	16,4	42,6
Hip angle (°)	27,45	11,1	13,7	41,3
Total time (s)	0,82	0,08	0,66	0,92
Velocity (cm/s)	301,21	22,16	270,2	344,56
Horizontal Velocity (Vₓ) (cm/s)	254,84	27,21	218,07	305,51
Vertical Velocity (Vᵧ) (cm/s)	156,67	32,87	90,01	202,03

Fig. 2.

Heatmap illustrating the correlations between the kinematic parameters of backstroke start performance and vertical jump performance, pelvic tilt, NYPA, and DB performance. *AP-DB: anterior–posterior dynamic balance, ML-DB: Medial–Lateral Dynamic Balance, PL-DB: Perimeter Lenght, NYPA: NewYork Posture Assessment, PT: Pelvic-Tilt

Table 2 presents the descriptive statistics of the demographic and anthropometric characteristics of the elite swimmers (n = 9) participating in the study, as well as the kinematic parameters related to their backstroke start performance. The participants’ mean age was 17.02 ± 1.81 years, and their mean training age was 8,13 ± 0.55 years. The mean FINA score was 711 ± 22.51, indicating that the athletes exhibited a high level of performance.

Regarding anthropometric characteristics, participants’ mean body weight was 72.01 ± 8.56 kg, mean height was 181.5 ± 8.7 cm, and mean BMI was 21.08 ± 1.32 kg/m². The mean upper extremity length was 84.5 ± 7.14 cm, arm span was 188.2 ± 10.91 cm, hand length was 20.02 ± 0.79 cm, lower extremity length was 102.75 ± 7.32 cm, limb length was 51.8 ± 17.53 cm, and foot length was 26.04 ± 2.07 cm. These results indicate a relatively homogeneous distribution of anthropometric characteristics that may influence swimming performance among the participants.

Regarding backstroke start kinematics, the mean time on-block was 0.67 ± 0.05 s, hip angle was 27.45° ± 11.10°, hip height was 46.76 ± 10.87 cm, flight time was 0.15 ± 0.06 s, flight distance was 244.53 ± 20.42 cm, and hand angle was 31.61° ± 6.86°. Additionally, the mean total time was 0.82 ± 0.08 s. For velocity parameters, mean velocity was 301.21 ± 22.16 cm/s, horizontal velocity (Vₓ) was 254.84 ± 27.21 cm/s, and vertical velocity (Vᵧ) was 156.67 ± 32.87 cm/s.

Figure 2 illustrates the correlations between the kinematic parameters of backstroke start performance and VJ, PT, NYPA, and DB. In the unadjusted Pearson correlation analysis, PT-Anterior was positively associated with hip angle (r = 0.667, p = 0.035), whereas PT-Posterior showed a positive association with velocity (r = 0.703, p = 0.023). In addition, NYPA score was negatively associated with water entry height (r = − 0.663, p = 0.037), and PL-DB demonstrated a negative association with water entry height (r = − 0.721, p = 0.019). No other associations reached statistical significance in the unadjusted analyses (p > 0.05).

To control for the risk of Type I error due to multiple testing, the Benjamini–Hochberg False Discovery Rate (FDR) procedure was applied across 90 simultaneous comparisons. After FDR correction, none of the observed associations remained statistically significant (all padj ≥ 0.692; Fig. 2). Therefore, the observed correlations should be interpreted with caution, as the limited sample size (n = 10) and the large number of simultaneous comparisons may have reduced statistical power.

Discussion

Swimming performance is a multidimensional construct consisting of the start, swimming, turn, and finish phases. Among these components, start performance is considered one of the most important determinants of overall performance, particularly in short-distance events [7, 17, 39].

The backstroke start is considered an important component of performance because it constitutes the initial acceleration phase of the race. The initial velocity achieved during the start may influence the distance covered during the flight phase, the water entry angle, and the characteristics of the transition into the underwater phase [42–45]. In particular, the water entry angle and body position are important for reducing the hydrodynamic resistance encountered during the underwater phase. An appropriate entry angle and hydrodynamic body alignment may contribute to maintaining the velocity gained at the start and performing underwater movements more effectively [41, 42]. Furthermore, start performance is not limited solely to force production at wall departure; maintaining momentum during the underwater phase and transitioning into the first stroke cycle are also important components of overall performance [42]. Therefore, identifying biomechanical and physical factors that may affect start performance is important for optimizing performance.

The aim of this study was to examine the relationships between the kinematic parameters of backstroke start performance (TB, HH, FT, WEH, HA, HIPA, TT, V, HV, and VV) and static posture parameters (PT-Anterior, PT-Posterior, PT-Lateral, and NYPA total score), dynamic balance parameters (AP-DB, ML-DB, and PL-DB), and VJ performance.

Before the Benjamini–Hochberg FDR correction, a positive relationship was observed between PT-Anterior and HIPA (r = 0.667, p = 0.035). Tor et al. [41] reported that the movement patterns of the pelvis and trunk segments were associated with start kinematics in elite backstroke swimmers. Similarly, Slawson et al. [36] reported that segmental alignment and body position are important biomechanical components of start performance.

Before the Benjamini–Hochberg FDR correction, a positive relationship was observed between PT-Posterior and V (r = 0.703, p = 0.023). The literature has reported that take-off velocity is one of the most important determinants of swimming start performance [6, 33, 43, 44, 45]. In particular, higher velocities achieved at wall departure have been shown to be associated with shorter start times and better 15 m performance [42]. In addition, during the backstroke start, the pelvis is defined as one of the key segments providing a mechanical link between the lower extremities and the trunk [41].

Before the Benjamini–Hochberg FDR correction, a negative relationship was observed between NYPA and WEH (r = − 0.663, p = 0.037). WEH is a fundamental kinematic variable describing the spatial position of the body during the flight phase and may influence water-entry mechanics [41, 42]. On the other hand, it has been reported that various postural adaptations may occur in the shoulder girdle, thoracic spine, and pelvic regions as a result of long-term swimming training ([4, 20]; Cejudo et al. 2020).

Before the Benjamini–Hochberg FDR correction, a negative relationship was observed between PL-DB and WEH (r = − 0.721, p = 0.019). During the backstroke start, the transition from the wall phase to the flight phase requires coordinated control of body segments. Dynamic balance performance is considered an indicator of the interaction among the proprioceptive, vestibular, and neuromuscular systems [34]. Furthermore, postural control has been reported to be an important component in the execution of complex sport-specific movements [23].

No significant relationship was observed between VJ and any kinematic parameter of start performance either before or after the Benjamini–Hochberg FDR correction. Although the literature has reported that lower-extremity force and power characteristics assessed by the VJ test are associated with swimming start performance [9, 26, 48], the majority of these studies have focused on freestyle, grab, or track start techniques. The backstroke start differs from other start techniques due to its initiation in the water, its distinct starting position, and the direction of force applied to the wall [41, 42].

The VJ test primarily evaluates the capacity for vertical force production. In contrast, backstroke start performance results from the interaction of numerous biomechanical factors, including the horizontal and oblique components of force applied to the wall, force application time, body position, and intersegmental coordination [41, 43–45]. Recent literature in sports performance has emphasized the principle of force specificity, indicating that performance outcomes depend not only on the magnitude of force produced but also on the direction of force application and task-specific movement characteristics [54, 55]. In this context, the absence of a relationship between VJ and backstroke start performance may be associated with the inability of land-based vertical jump tests to adequately represent the unique mechanical demands of the backstroke start. Nevertheless, future studies may consider using tests that better reflect horizontal force production during the backstroke start in order to further clarify the role of lower-extremity force in backstroke start performance. However, the fact that none of the relationships remained statistically significant after the Benjamini–Hochberg FDR correction requires the findings to be interpreted as exploratory in nature. In particular, it should be considered that the limited sample size and multiple comparisons may have reduced statistical power.

Conclusıon

In conclusion, although significant relationships were observed between PT-Anterior and HIPA, PT-Posterior and V, NYPA and WEH, and PL-DB and WEH before the Benjamini–Hochberg FDR correction, none of these relationships remained statistically significant after the correction for multiple comparisons.

Nevertheless, the findings suggest that postural characteristics and dynamic balance performance may be associated with specific kinematic components of the backstroke start. In contrast, no relationship was found between VJ performance and the kinematic parameters examined. This result suggests that land-based vertical jump tests may not fully reflect the unique biomechanical demands of the backstroke start.

Considering the limited sample size and the exploratory nature of the findings, future studies with larger samples are needed to better understand the potential role of postural characteristics, dynamic balance, and lower-extremity performance in backstroke start mechanics.

Limitations

This study has several limitations. First, the limited sample size may have reduced the statistical power of the analyses and contributed to the loss of statistical significance for all observed associations following the application of the Benjamini–Hochberg FDR correction for multiple comparisons. Therefore, the findings of the present study should be interpreted as exploratory in nature.

Another limitation of this study is the absence of formal intra-rater and inter-rater reliability assessments for the kinematic variables obtained using Kinovea, the NYPA evaluations, and the TecnoBody PK200 measurements. Future studies should establish the reproducibility of these measures to strengthen confidence in their use and further support their application in swimming-related research.

Abbreviations

AP-DB

Anterior–Posterior Dynamic Balance

ML-DB

Medial–Lateral Dynamic Balance

PL-DB

Perimeter Length

NYPA

NewYork Posture Assessment

PT

Pelvic-Tilt

VJ

Vertical Jump

TB

Time on Block

HH

Hip Height

FT

Flight Time

WEH

Water Entry Height

HA

Hand Angle

HIPA

Hip Angle

TT

Total Time

V

Velocity

HV

Horizontal Velocity

VV

Vertical Velocity

Authors’ contributions

Conceptualization: EŞC, ŞŞC; Methodology: EŞC, ŞŞC, ŞŞ; Software: EŞC; Formal analysis: EŞC; Investigation: EŞC, ŞŞC, ŞŞ; Data Curation: EŞC, ŞŞC, ŞŞ; Visualization: EŞC; Supervision & Validation: ŞŞC; Project administration: EŞC, ŞŞ, ŞŞC; Writing- Original Draft: EŞC, ŞŞC, ŞŞ; Writing—Review & Editing: EŞC, ŞŞ, ŞŞC.

Funding

This study was derived from a master’s thesis conducted at the Graduate School of Manisa Celal Bayar University. No financial support was received from any institution in 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

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. The research protocol received ethical approval from the Health Sciences Ethics Committee of Manisa Celal Bayar University (approval number: 20.478.486). We confirm that all participants provided informed consent before taking part in the study. This ensures that they were fully aware of the study’s purpose, procedures, potential risks, and their right to withdraw at any time.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.