Do Lower-Body Dimensions and Body Composition Explain Vertical Jump Ability?

Association between the dry-land strength & power and the kick start kinetics in elite male and female swimmers

The aim of this research was to determine the association between dry-land exercises and the start kinetics in elite swimmers. Fourteen swimmers (eight males and six females) included in a national team took part in this study. A fixed smith-machine was used to measure the maximal full squat strength (Smax). The height of squat (SJ) and countermovement (CMJ) jumps were collected with a contact mat. The ground reaction force of the kick starts in the three-dimensional axis (Fz horizontal; Fy, vertical; Fx, lateral) was obtained by an instrumented force plate in the starting block. Overall, the Smax showed a high and significant association with Fz (r = 0.60) and Fy (r = 0.87). Moderate and significant associations were found between Fy and SJ (r = 0.51) and CMJ (r = 0.57). While Smax in males showed high association with Fy (r = 0.77), the Smax for females showed greater association with Fz (r = 0.84). As conclusion, the full back squat seems to be the dry-land exercise with higher association with the kick start kinetics. While in males the full squat defines better the vertical component, for females it defines the horizontal one.

30 Years of Change: Declining Motor Fitness and Anthropometric Shifts in Polish University Students (1994-2024)

BACKGROUND

To assess changes in the anthropometric and motor characteristics of male and female Polish university students between 1994 and 2024.

METHODS

The first study was conducted in 1994 on 712 female and 495 male university students aged 19-25 years (19.94 ± 1.09), and the second study was conducted in 2024 on 323 female and 339 male university students aged 19-25 years (19.92 ± 1.08). The participants' body mass and height were measured, and the students participated in a modified version of Pilicz's test consisting of four motor ability tests. The changes in the students' performance over time were also analyzed in the context of their socioeconomic status (SES), including the place of permanent residence and the parents' education.

RESULTS

The students' BMI values (as well as body mass and body height in female students) were significantly higher (p < 0.001) in 2024 than in 1994. The male students examined in 1994 demonstrated significantly higher strength abilities in the medicine ball forward throw test. In turn, the females studied in 1994 received significantly better scores in motor ability tests, including the zig-zag run, 1-Minute Burpee Test, and the medicine ball forward throw (29.4 s, 22 cycles, 591.3 cm, respectively) than those examined in 2024 (30.1 s, 19.3 cycles, and 463.3 cm, respectively). The variations in the results were similar when the participants' SES was considered in the analysis, which suggests that these factors had no significant effect on the analyzed characteristics over time.

CONCLUSIONS

This study revealed a greater decline in the anthropometric and motor characteristics of female than male university students over a period of 30 years. The observed changes were not influenced by SES factors such as the place of permanent residence or the parents' education.

Performance of artificial neural network compared to multi-linear regression in prediction of countermovement jump height

Previous research has used primarily linear regression models to predict jump height and establish contributors of performance. The purpose of this study was to compare the performance of artificial neural network (ANN) and multi-linear regression (MLR) in prediction of countermovement jump (CMJ) height and investigating the contribution of kinematic variables to CMJ performance. Thirty-four healthy young male athletes performed a total of 204 CMJ while eight kinematic variables (the hip, knee, and ankle angles at the begging of the concentric phase of CMJ, the hip and knee take-off angles, and the shoulder, hip, and knee maximum angular velocities) were used as inputs to ANN and MLR to predict CMJ height. The correlation coefficients between the jump height and the predicted value by the developed models indicated that ANN predict CMJ height better than MLR (R2 = 0.68 compared to R2 = 0.44). Moreover, the root mean squared error of prediction showed better performance of the ANN rather than the MLR (4.8 cm compared to 5.3 cm). The shoulder and hip maximum angular velocities were the most important contributors, and then the hip and knee take-off angles contributed to CMJ height. In conclusion, implementing ANN to identify key variables of performance may also be relevant for other sport skills.

Body fat of competitive volleyball players: a systematic review with meta-analysis

BACKGROUND

Reference values of body fat for competitive volleyball players are lacking, making it difficult to interpret measurement results. This review systematically summarized published data on the relative body fat of volleyball players and calculated potential differences between sex, measurement method, and competitive level.

METHODS

The protocol followed the Preferred Reported Items for Systematic Reviews and Meta-Analysis guidelines. The literature search was conducted using five electronic databases to retrieve all relevant publications from January 1, 2010, to July 1, 2021. The 63 studies including 2607 players that met the inclusion criteria were analyzed using random-effects models. Data were reported as pooled mean body fat with 95% confidence intervals.

RESULTS

Body fat for males and females was 12.8% (11.9-13.8%) and 22.8% (21.9-23.7%), respectively. Body fat was 18.3% (16.3-20.4%) measured via skinfolds, 18.4% (15.6-21.2%) via bioelectrical impedance analysis, 24.2% (20.4-28.0%) via dual-energy x-ray absorptiometry and 21.6% (17.4-25.8%) via densitometry. Regional, national, and international-level players had body fat values of 19.5% (17.8-21.2%), 20.3% (18.6-22.0%), and 17.9% (15.7-20.4%), respectively. When the meta-regression was adjusted for the variables sex, measurement method, and competitive level, a significant difference between sex (p < 0.001), dual-energy x-ray absorptiometry and skinfolds (p = 0.02), and national and international-level players (p = 0.02) was found. However, sensitivity analysis revealed that findings regarding measurement method and competitive level were not robust and should, therefore, be interpreted with caution.

CONCLUSIONS

Despite the limitations of published data, this meta-analysis provided pooled values for body fat of male and female volleyball players for different competitive levels and measurement methods.

Patellofemoral Pain, Q-Angle, and Performance in Female Chinese Collegiate Soccer Players

Background and objective: Female sports injuries have been neglected by science, and few relevant studies have considered female subjects. Knee pain in female soccer players is more common than in male soccer players. The number of days of absence from training and competition has been shown to be higher in females than males. The reporting of knee pain is common in female soccer players, but whether knee pain is associated with morphological features is unclear. The Q-angle of the knee has been hypothesized to be a causal factor in knee pain. Asian females have shown higher levels of valgus than non-sporting Caucasian populations, but no data exist for female Chinese players. The aim of our study was to investigate whether there are associations between knee pain, the Q-angle of the lower limb, jump performance, play time, and perceived exertion in female Chinese collegiate soccer players. Materials and Methods: We measured the Q-angle, patellofemoral/anterior knee pain (SNAPPS questionnaire), and CMJ and SJ performance of 21 subjects (age: 20.09 ± 1.13 years, weight: 56.9 ± 6.26 kg, height: 164.24 ± 4.48 cm, and >10 years of practice) before and after a match; Borg scale and play time results were also recorded. Results: We found that our studied group had higher Q-angles in comparison to other ethnic groups reported in the literature, as well as an association of the Q-angle with the age, height, and weight of the players; however, contrary to other studies, we did not find any association between the Q-angle and knee pain, jumps, play time, or perceived exertion. Knee pain was not associated with any of the measured variables. Conclusions: Female Chinese soccer players showed higher Q-angles than players of other ethnic groups, a result that was associated with anthropometrics. The Q-angle was not found to be associated with knee pain, for which the sole determinant was body height.

Speed and Agility Predictors among Adolescent Male Football Players

This study aimed to examine the associations between lower-body explosive strength (squat jump-SJ, and countermovement jump-CMJ), speed (10- and 35-m linear sprints), and agility (t-test) capacities, after controlling for crucial predictors such as chronological age (CA) and body composition. The sample was composed of 164 adolescent male football players from under 19, under 17, and under 15 age groups. Body fat percentage (BF%) was significantly and positively related to body mass, speed, and agility. In contrast, BF% was a significant negative predictor of lower-body explosive strength. Sprint and t-test times were significantly and negatively correlated with lower-body explosive strength. After controlling for CA and body composition, SJ was the most significant predictor, accounting for 36 to 37% of the variance observed in the 35 m linear sprint and the t-test performance. Our main results suggest that lower-body explosive strength, particularly in the SJ, is a significant predictor of male adolescent male football players' speed and agility capacities. Conversely, detrimental relationships between BF% and these outcomes were observed. Sports agents should consider lower-body explosive strength development as part of the youth football training process, particularly to improve maximal sprint and change of direction times, which are crucial to game performance.

Physical Activity and Physical Fitness among University Students-A Systematic Review

The aim of this systematic review was to examine the scientific evidence regarding physical activity and physical fitness among university students. The search and analysis of the studies were done in accordance with the PRISMA guidelines. An electronic databases search (Google Scholar, PubMed, Science Direct, and Scopus) yielded 11,839 studies. Subsequently, the identified studies had to be published in English between 2011 and 2021, the experimental study had to have included males and females attending a faculty, and the participants had to have been evaluated for physical activity and fitness. A total of 21 studies were included in the quantitative synthesis, with a total of 7306 participants, both male and female. After analyzing the obtained results, it could be concluded that university students show a satisfactory level of physical activity and physical fitness. However, the results vary due to different factors involved, mostly related to the cultural differences and educational systems in different countries. As this study observes mediocre results of physical activity and physical fitness among university students, it is crucial to get their attention and awareness, to at least maintain a satisfactory level of physical activity and physical fitness.

Elite Male Volleyball Players Are at Risk of Insufficient Energy and Carbohydrate Intake

Elite volleyball athletes experience significant physical and psychological demands during the competitive season. The aim was to compare the dietary intake of male volleyball athletes with recommendations for sport and health, and to examine the association of physique traits and knee health on eating behaviours and of eating behaviours on reported dietary intake. Using a retrospective cross-sectional design, 22 male athletes from a national indoor volleyball program underwent anthropometric, dual-energy X-ray absorptiometry and resting metabolic rate testing, 4-day dietary intake and hematological analysis, and also completed the three-factor eating questionnaire–R18 for eating behaviours and the Victorian Institute of Sport Assessment—patellar tendon (VISA-P) questionnaire for knee health. Most players under-consumed energy compared to reference guidelines, secondary to under-consuming carbohydrate for exercise. The primary eating behaviour was cognitive restraint, which was associated with body mass index and ectomorphy. Emotional eating behaviour was associated with VISA-P. Differences in emotional and cognitive restraint eating behaviours did not impact dietary intake. The findings suggest that players are at risk of an impaired ability to adapt to and recover from training during an important segment of the competitive season. Future work should explore the presence of low energy availability in elite male volleyball players.

Potential Predictors of Vertical Jump Performance: Lower Extremity Dimensions and Alignment, Relative Body Fat, and Kinetic Variables

ABSTRACT

Daugherty, HJ, Weiss, LW, Paquette, MR, Powell, DW, and Allison, LE. Potential predictors of vertical jump performance: Lower extremity dimensions and alignment, relative body fat, and kinetic variables. J Strength Cond Res 35(3): 616-625, 2021-The association of structural and kinetic variables with restricted vertical jump (RVJ) displacement without and with added mass was examined in 60 men and women. Added mass (weighted vest) simulated a 5% increase in body fat (BF%). Independent variables included BF%, thigh length, and static Q-angle (Q-angles), and while performing RVJ, different expressions of frontal-plane knee angle (FPKA), dynamic Q-angle (Q-angled), vertical ground reaction force (vGRF), concentric vertical impulse (Iz), concentric rate of force development (CRFD), and vertical power (Pz). Variables having significant (p ≤ 0.05) negative correlations with RVJ displacement included BF% (r = -0.76) and Q-angles (r = -0.55). Those having significant (p ≤ 0.05) positive correlations with RVJ displacement included peak and average concentric Pz (r range = 0.74-0.81), peak and average concentric vGRF (r range = 0.46-0.67), Iz (r range = 0.32-0.54), thigh length (r = 0.31), minimum Q-angled (r = 0.31), and maximum FPKA (r = 0.28). Variables not associated (p > 0.05) with RVJ displacement included minimum and excursion FPKA (r = 0.11 and 0.23), maximum, excursion, and average Q-angled (r = 0.24, 0.11, and 0.22), and CRFD (r range = 0.19-0.24). A simple regression model predicted RVJ displacement (p = 1.00) for the simulated 5% increase in body fat. To maximize jumping performance, (a) high levels of body fat should be avoided, (b) peak and average Pz, vGRF, and Iz should be maximized through training, and (c) having a lower Q-angles is associated with better jumping ability.

Variable Lower Limb Alignment of Clinical Measures With Digital Photographs and the Footscan Pressure System

OBJECTIVE

This study examines the effect of the lower limb misalignment and its possible compensatory effect on plantar pressure in a normal population. The aim of this paper is to present a structured method for the analysis of posture and its changes using a standardized digital photography technique and plantar pressure measuring device.

DESIGN

Cohort.

SETTING

Laboratory.

PARTICIPANTS

A total of 200 adult volunteers between 18 and 22 years of age who had no current symptoms of pain and foot or ankle pathology participated in the study.

MAIN OUTCOME MEASURES

The gold standard measure of lower limb alignment with weight-bearing status is the mechanical axis and their angles using Image J software. Structural and functional measurements of the same foot were taken using a plantar pressure measuring device. In this study, 5 alignment (thigh, knee, leg, ankle, and foot) characteristics were measured on the lower limb using the 2 techniques, and, additionally, the foot contact area, peak pressure, foot axis, rearfoot angle, and subtalar joint flexibility score were analyzed in 10 different regions of the foot.

RESULTS

This study has shown a reasonable correlation between digitalized measurements and plantar pressures values. Quadriceps angle affected midfoot impulse, foot axis angle, subtalar joint minimum angle, and rearfoot angle positively. Subtalar joint flexibility scores were analyzed in 10 different regions of the foot. There was a positive correlation between rearfoot angle and quadriceps angle (P = .009, r = .261). Results of both methods show that they endorse each other.

CONCLUSIONS

The posture of the standing feet may have influence on lower limb alignment. Currently, there are no studies carried out by using digital photogrammetry and foot scan. The authors claim that patient-friendly digital photogrammetry would have a positive contribution to the monitoring of patients, even including new ones in the treatment programs, reducing any possible loss in the personal and national economy.

Effects of a Gluteal Muscles Specific Exercise Program on the Vertical Jump

The vertical jump is a complex movement where many factors are involved in the final result. Currently, how a specific exercise program for gluteal muscles can affect the vertical jump is unknown. So, the aim of this study was to examine the effect of a specific exercise program for the gluteal muscles on a vertical jump. Forty-nine amateur athletes completed an 8-week program. The experimental group received a specific gluteal muscle training program in addition to their regular training routine, whereas the control group received their regular training routine. Jump height, flight time, speed and power were assessed (baseline, postintervention, and 4-week follow-up). Repeated-measures analyses of variance were conducted with ∝ ≤ 0.05. We calculated Eta squared effect sizes with 95% confidence intervals. Measurements at 8 weeks revealed significant increases in the experimental group compared to the control group for the values: jump height (p < 0.05) (experimental group = 17.15%; control group = 3.09%), flight time (p < 0.001) (experimental group = 7.98%; control group = 3.52%), speed (p < 0.01) (experimental group = 1.96%; control group = 1.83%) and power (p < 0.05) (experimental group = 4.43%; control group = 0.32%). However, at follow-up, these changes were not maintained. These data suggest that this specific training protocol for the gluteal muscles is effective in order to improve vertical jump performance in amateur athletes who use the vertical jump in their routine training habits.