Jump and Change of Direction Speed Asymmetry Using Smartphone Apps: Between-Session Consistency and Associations With Physical Performance

Relationship between lower extremity strength asymmetry and linear multidimensional running in female tennis players

Background

Tennis requires movement abilities in changing playing situations. This article investigates the relationship between lower extremity strength asymmetry ratio and linear and multidimensional running performances in female tennis players.

Methods

A total of 56 female tennis players, with a mean age of 15.44 ± 0.50 years, participated in the study-the research design involved three sessions at 48-hour intervals. In the first session, athletes performed dominant and non-dominant countermovement jump (CMJ) and board jump (BJ) tests. The second (sec) session included 10-meter (-m) and 30-m linear running performance tests, while the final session assessed multidimensional running performance with a change of direction (COD) test. The relationship between CMJ and BJ asymmetry ratios and linear and multidimensional running performances was analysed using the Pearson correlation coefficient. Bilateral asymmetry rates in linear and multidimensional running performance were determined through linear regression analysis.

Results

The dominant CMJ recorded 17.56 ± 3.47 cm, while BJ was 130.23 ± 21.76 cm, and the non-dominant CMJ measured 16.79 ± 4.51 cm with a BJ of 147.52 ± 30.97 cm. The athletes had a CMJ asymmetry rate of 12.67 ± 11.29% and a BJ asymmetry rate of 7.19 ± 5.28%. A relationship was seen between the CMJ asymmetry rate and 30-m running performance (r = 0.368, p < 0.05). There was no correlation between BJ asymmetry rate and 10-m running performance. Significant correlations were found between 30-m (r = 0.364) and COD (r = 0.529) running performances (p < 0.05).

Conclusions

It can be said that the CMJ asymmetry ratio may negatively affect 30-m and the BJ asymmetry ratio may negatively affect 30-m and COD performance.

Reliability and validity of "My Jump 2" application for countermovement jump free arm and interlimb jump symmetry in different sports of professional athletes

Background

Vertical jumping is an important evaluation tool to measure muscle strength and power as well as lower limb symmetry. It is of practical importance and value to develop and utilize a portable and low-cost mobile application (APP) to evaluate jumping. The "My Jump 2" app is an iPhone camera-based application for measuring jumping movements, which is applied to the countermovement jump (CMJ) vertical jumps of the lower limbs of athletes in different sports. The validity of this application and previous versions applied to different forms of vertical jump tests has been preliminarily demonstrated in different population, which has an obvious progress in research. Therefore, the reliability and validity of the jump height, time of flight parameters and symmetry of the CMJ vertical jump of athletes in different sports are needed to be verified by more experiments.

Purpose

The purpose of this study is to verify whether "My Jump 2" can effectively and reliably assess jump height, flight practice and lower limb symmetry in CMJAM (countermovement jump free arm) tests in fencing, swimming and diving athletes.

Methods

Seventy-nine fencers, swimmers and divers with training experience participated in this study. They completed a total of three CMJAM vertical jump and lower limb symmetry tests in 1 day, while being assessed by using the "My Jump 2" application and a force platform. The intra-group correlation coefficient (ICC) was used to verify reliability, while the Cronbach's alpha and coefficient of variation (CV%) was used to analyze the stability of the CMJAM vertical jump test over three jumps. The Pearson correlation coefficient was used to verify the strength of the relationship between methods (i.e., concurrent validity), and the Bland-Altman plot was used to represent consistency, meanwhile, the t-test was used to determine the systematic bias between methods.

Results

Compared with the force platform, the cumulative height values of the total number of jumps (r = 0.999; p = 0.000), the cumulative time to vacate (r = 0.999; p = 0.000) for the CMJAM test obtained by the "My Jump 2" application, the height (ICC = 0.999-1, p = 0.000), the time to vacate flight (ICC = 0.999-1, p = 0.000), contact time symmetry (ICC = 0.976-0.994, p = 0.000), and flight time symmetry (ICC = 0.921-0.982, p = 0.000), respectively. Showed high correlation between the results of "my jump 2" app and the force platform.

Conclusion

The "My Jump 2" application is a valid tool to assess CMJAM vertical jump and lower limb symmetry in fencing, swimming and diving athletes with training experience.

Things to keep in mind when selecting physical assessments in youth soccer: Correlations between test performances, interlimb asymmetries, and effects of maturation

A range of field-based tests have been proposed for inclusion in physical performance assessment batteries. However, there are obvious time and human resources constraints in applied settings. The knowledge of potential relationships between tests on performance, asymmetries, as well as maturation-induced changes, may help select the most informative and least time-consuming testing battery. The purposes of this study were: (1) to determine correlations in performance between different field-based tests, in interlimb asymmetry between those unilateral tests, and between asymmetry scores and test performances, and (2) to determine the influence of players' maturity status on test performances and asymmetries. A total of 309 male youth soccer players completed a nine-test battery including y-balance test, drop vertical jump, countermovement jump, single leg countermovement jump, standing long jump, single leg hop for distance, Illinois agility test, 10 m sprint, and 20 m sprint. The results revealed moderate-to-very large relationships between jump, sprint, and agility performances (r = 0.43-0.94), but weak-to-moderate correlations between these tests and balance scores (r ≤ 0.38). No relevant relationship (r ≤ 0.32) for asymmetries detected through different unilateral tests was found, nor between asymmetries and performance scores (r < 0.29). While maturity status clearly influenced players' performance, a limited impact on asymmetries was evident. Despite the mentioned relationships, the low shared variance between tests indicates that they should not be used interchangeably, and coaches should select those with the greatest specificity for the sport. Asymmetries do not influence performance, but their prevalence and unchanging nature with maturation can be seen as an opportunity for the identification of highly asymmetrical players and the application of interventions to improve the weaker limb, irrespective of the athlete's stage of development. To this end, the single leg countermovement jump might be viewed as an appropriate test in male youth soccer.

Change of Direction Asymmetry in Youth Elite Tennis Players: A Longitudinal Study

Longitudinal investigations into the development of inter-limb asymmetry in sports are scarce. This study examined the development of change of direction (COD) asymmetry magnitude in youth elite tennis players. Dominant (overall best performance) and non-dominant (best performance on the other side) scores and COD asymmetry magnitude were quantified annually (up to six years) in 323 male and 235 female players (ages 6 to13 years). Linear mixed effects regression models examined the development of COD performance and asymmetry magnitude according to players' chronological age and sex. Kappa coefficients examined the consistency for the direction of asymmetry across test occasions. Regardless of sex, COD performance significantly improved (p<0.001) while COD asymmetry magnitude significantly decreased (- 0.17±0.87% / year) with increasing chronological age. Regardless of age, males showed significantly lower COD times (- 0.111±0.091 s) and lower COD asymmetry magnitude (- 0.30±1.00%) compared to females. The slight and poor (k-value=0.02-0.00) kappa coefficients for males and females, respectively, highlight the direction specificity of functional asymmetry. These data show that whereas performance of the COD test improved, the magnitude of COD asymmetry declined across chronological age in youth tennis players.

Validity and reliability of "My Jump app" to assess vertical jump performance: a meta-analytic review

This systematic review and meta-analysis aims to investigate the validity and reliability of the My Jump smartphone application in measuring vertical jump height, specifically using flight-time-based measures. To identify potential studies for inclusion, a comprehensive search strategy was employed in PubMed, Web of Science, Scopus, and EBSCO host databases. Validity was assessed in two ways: (1) mean and standard deviations of My Jump measurements were compared to criterion methods to assess the agreement of raw scores; (2) correlation coefficients evaluated the within-group consistency of rankings between My Jump and criterion methods. Reliability was assessed using intraclass correlation coefficients (ICC). Heterogeneity was evaluated via Cochrane's Q statistic, its p-value, I2 value, and tau2 value. Publication bias was explored through funnel plot symmetry and confirmed with extended Egger's test. Following the search, 21 studies met the inclusion criteria. Results showed no significant difference in raw scores between My Jump and criterion methods, indicating high agreement. High correlation was also found for within-group rankings, suggesting consistency. The My Jump application demonstrated nearly perfect reliability scores. The My Jump application appears to be a valid and reliable tool for sports scientists and strength and conditioning practitioners, offering a cost-effective and accessible means for accurately assessing vertical jump performance in various settings. However, it should be noted that these results are specific to flight-time-based measures, and further research is needed to validate these findings against gold-standard take-off velocity methods.

Why Sports Should Embrace Bilateral Asymmetry: A Narrative Review

(1) Background: Asymmetry is ubiquitous in nature and humans have well-established bilateral asymmetries in their structures and functions. However, there are (mostly unsubstantiated) claims that bilateral asymmetries may impair sports performance or increase injury risk. (2) Objective: To critically review the evidence of the occurrence and effects of asymmetry and sports performance. (3) Development: Asymmetry is prevalent across several sports regardless of age, gender, or competitive level, and can be verified even in apparently symmetric actions (e.g., running and rowing). Assessments of bilateral asymmetries are highly task-, metric-, individual-, and sport-specific; fluctuate significantly in time (in magnitude and, more importantly, in direction); and tend to be poorly correlated among themselves, as well as with general performance measures. Assessments of sports-specific performance is mostly lacking. Most studies assessing bilateral asymmetries do not actually assess the occurrence of injuries. While injuries tend to accentuate bilateral asymmetries, there is no evidence that pre-existing asymmetries increase injury risk. While training programs reduce certain bilateral asymmetries, there is no evidence that such reductions result in increased sport-specific performance or reduced injury risk. (4) Conclusions: Bilateral asymmetries are prevalent in sports, do not seem to impair performance, and there is no evidence that suggests that they increase injury risk.

Between-session reliability of performance and asymmetry variables obtained during unilateral and bilateral countermovement jumps in basketball players

This study aimed to evaluate the between-session reliability of single-leg performance and asymmetry variables during unilateral and bilateral countermovement jumps (CMJ). Twenty-three basketball players completed two identical sessions which consisted of four unilateral CMJs (two with each leg) and two bilateral CMJs. Mean and peak values of force, velocity and power, impulse, and jump height were obtained separately for each leg using a dual force platform. All performance variables presented an acceptable reliability (CVrange = 4.05-9.98%) with the exceptions of jump height for the unilateral CMJs and mean power, peak velocity, peak power, and impulse for the left leg during the bilateral CMJ (CV≥11.0%). Nine out of 14 variables were obtained with higher reliability during the unilateral CMJ (CVratio≥1.16), and 4 out of 14 during the bilateral CMJ (CVratio≥1.32). Asymmetry variables always showed an unacceptable reliability (ICCrange = 0.15-0.64) and poor/slight levels of agreement in direction (Kapparange = -0.10 to 0.15) for the unilateral CMJ, while an acceptable reliability (ICCrange = 0.74-0.77) and substantial levels of agreement in direction (Kapparange = 0.65 to 0.74) were generally obtained for the bilateral CMJ. These results suggest that single-leg performance can be obtained with higher reliability during the unilateral CMJ, while the bilateral CMJ provides more consistent measures of inter-limb asymmetries.

Inter-Limb Jump Asymmetries and Their Association with Sport-Specific Performance in Young Male and Female Swimmers

This study aimed to examine inter-limb jump asymmetries and their association with sport-specific performance in young swimmers. Thirty-eight (male, n = 19; female, n = 19) regional/national level young swimmers (age: 12.3 ± 1.2 years; height: 159.6 ± 8.2 cm; body mass: 52.5 ± 9.2 kg) participated in this study. Inter-limb asymmetries were assessed for single-leg countermovement jump (_SLCMJ) and single-leg standing long jump (_SLSLJ). Sport-specific performance was evaluated using front crawl (i.e., 50 m and 25 m) and front crawl kick (i.e., 50 m and 25 m). The kappa coefficient revealed a "slight" level of agreement (Κ = 0.156, 0.184, and 0.197 for female, male, and all, respectively) between the direction of asymmetry for _SLCMJ and _SLSLJ, indicating that asymmetries rarely favored the same limb during both tests. A paired sample t-test showed a significant difference (p = 0.025) between asymmetry scores obtained in _SLCMJ and _SLSLJ. No significant difference was found in asymmetry scores between males and females (p = 0.099 to 0.977). Additionally, no association between asymmetry scores and sport-specific performance was observed (p > 0.05). Our findings highlight the independent nature of inter-limb asymmetries derived from _SLCMJ and _SLSLJ among young male and female swimmers. Further, our results suggest no association between jumping asymmetries and sport-specific performance.

A Technical Report on Reliability Measurement in Asymmetry Studies

ABSTRACT

Bailey, CA, Sato, K, and McInnis, TC. A Technical report on reliability measurement in asymmetry studies. J Strength Cond Res 35(7): 1779-1783, 2021-Much of the current literature on asymmetry in sport performance may be biased by evaluating reliability before quantifying the asymmetry metric. This technical report aimed to evaluate the reliability of asymmetry measurements in countermovement jumps (CMJs) by providing measures before production of asymmetry metrics, after production of scalar- and vector-based asymmetry metrics, and to analyze the resulting differences that can lead to misinformed decision making. Thirteen collegiate baseball players (19.9 ± 1.3 years, 82.2 ± 10.9 kg) participated in CMJ testing on 2 force plates to evaluate symmetry index (SI) scores as scalar (asymmetry magnitude only) and vector (asymmetry magnitude and direction) quantities. Relative and absolute reliability were evaluated for peak force (PF), scalar PF SI, and vector PF SI. Results showed that reliability measures produced on the constituent force-time variable provide much more favorable results compared with evaluating reliability of the asymmetry measure itself (coefficients of variation of 10.4-15.7% vs. 63.2-1,497.1%). Findings also showed that reliability is altered depending on whether asymmetry is quantified as a scalar or vector. Asymmetry should likely be quantified as a vector for reliability purposes because that allows variability in both magnitude and direction. These findings demonstrate that inadequate evaluation of reliability in asymmetry leads to biased results. Practitioners should use caution when considering the results of asymmetry assessments as they may not be as reliable as they are often portrayed.

Unilateral or Bilateral Standing Broad Jumps: Which Jump Type Provides Inter-Limb Asymmetries with a Higher Reliability?

This study aimed to compare the between-session reliability of performance and asymmetry variables between unilateral and bilateral standing broad jumps (SBJ). Twenty-four amateur basketball players (12 males and females) completed two identical sessions which consisted of four unilateral SBJs (two with each leg) and two bilateral SBJs. Mean and peak values of force, velocity and power, and impulse were obtained separately for each leg using a dual force platform. Inter-limb asymmetries were computed using the standard percentage difference for the unilateral SBJ, and the bilateral asymmetry index-1 for the bilateral SBJ. All performance variables generally presented an acceptable absolute reliability for both SBJs (CV range = 3.65-9.81%) with some exceptions for mean force, mean power, and peak power obtained with both legs (CV range = 10.00-15.46%). Three out of 14 variables were obtained with higher reliability during the unilateral SBJ (CVratio ≥ 1.18), and 5 out of 14 during the bilateral SBJ (CVratio ≥ 1.27). Asymmetry variables always showed unacceptable reliability (ICCrange = -0.40 to 0.58), and slight to fair levels of agreement in their direction (Kappa range = -0.12 to 0.40) except for unilateral SBJ peak velocity [Kappa = 0.52] and bilateral SBJ peak power [Kappa = 0.51]) that showed moderate agreement for both SBJs. These results highlight that single-leg performance variables can be generally obtained with acceptable reliability regardless of the SBJ variant, but the reliability of the inter-limb asymmetries in the conditions examined in the present study is unacceptable to track individual changes in performance.

Seasonal Variation of Physical Performance and Inter-limb Asymmetry in Professional Cricket Athletes

ABSTRACT

Bishop, C, Weldon, A, Hughes, J, Brazier, J, Loturco, I, Turner, A, and Read, P. Seasonal variation of physical performance and interlimb asymmetry in professional cricket athletes. J Strength Cond Res 35(4): 941-948, 2021-The aims of this study were to: (a) determine the seasonal variation of physical performance in professional cricket players and (b) determine the seasonal variation of interlimb asymmetries in the same cohort of professional players. Fifteen male professional cricket players (age: 20.60 ± 1.59 years; height: 1.82 ± 0.08 m; and body mass: 78.70 ± 11.23 kg) performed unilateral countermovement jumps (CMJs), unilateral drop jumps, 10 m sprints and 505 change of direction (COD) speed tests at pre (March), mid (June), and end (September) of the 2018 season. Interlimb asymmetry was quantified in the unilateral CMJ (jump height and concentric impulse), unilateral drop jump (jump height and reactive strength index [RSI]), and 505 (total time and COD deficit). Significant changes (p < 0.05) were evident for the following tests: unilateral CMJ (effect size [ES] range = 0.67-1.00), 505 on the right leg (ES = 0.70), 10 m (ES range = -1.39 to 0.70), and COD deficit (ES range = 0.70-0.80), with the largest changes evident for 10-m sprint. No significant differences were evident in drop jump performance throughout the season. For the magnitude of asymmetry, significant changes in jump height asymmetry from the unilateral CMJ were evident from mid to end of season (ES = 0.72). For the direction of asymmetry, levels of agreement ranged from poor to substantial in the unilateral CMJ (kappa = -0.21 to 0.72), fair to substantial in the unilateral drop jump (kappa range = 0.33 to 0.74), and slight to moderate during the 505 test (kappa range = 0.06 to 0.44), with RSI showing noticeably better results than other tests or metrics. These data show that the largest changes in performance scores throughout the season came from the 10-m test, which practitioners may wish to consider implementing if not doing so already. Furthermore, both unilateral jump tests showed their use for asymmetry interpretation, which practitioners may wish to consider implementing in to their test batteries. Specifically, jump height asymmetry during the unilateral CMJ was the only metric to exhibit meaningful changes between time points, whereas RSI was the metric that exhibited more consistent limb dominance characteristics for the direction of asymmetry.