Lower Limb Explosive Strength Research Articles

Modelling Developmental Changes in Repeated-Sprint Ability by Chronological and Skeletal Ages in Young Soccer Players

This study investigated the influence of chronological (CA) and skeletal ages (SA), anthropometry, aerobic endurance and lower limb explosive strength on developmental changes in repeated-sprint ability (RSA) in soccer players aged 11-17 years. Participants were annually followed over 5 years, resulting in 366 measurements. Multilevel regression modelling analysed longitudinal data aligned by CA and SA (Model 1 and 2, respectively). After diagnosing for multicollinearity, it was possible to predict RSA with 2-level hierarchical models [Model 1 (CA as Level 2 predictor): Log-Likelihood=1,515.29, p<0.01; Model 2 (SA as Level 2 predictor): Log-Likelihood=1,513.89, p<0.01]. Estimating sum of sprints for young soccer players are given by equations: sum of sprints=84.47 - 1.82 × CA + 0.03 × CA2 - 0.05 × aerobic endurance - 0.10 × lower limb explosive strength -0.09 × fat-free mass + 0.13 × fat mass (Model 1); 73.58 - 0.43 × SA - 0.05 × aerobic endurance - 0.10 × lower limb explosive strength - 0.08 × fat-free mass - 0.45 × training experience + 0.13 × fat mass (Model 2). The models produced performance curves that may be used to estimate individual performance across adolescent years. Finally, the validity of each model was confirmed based on corresponding measurements taken on an independent cross-sectional sample.

Capacidad de salto y equilibrio en jóvenes y ancianos físicamente activos

Introduction and aimsThe risk of falls in the elderly populations due to loss of balance increases with age. The aim of the present study is to analyse the relationship between lower limb explosive strength and the ability to maintain balance in two different samples of active young and elderly subjects. Material and methodsSubjects included in the study were 8 elderly and 11 young volunteers, all of them physically active. Counter-movement jump tests and one-leg static balance tests using a foam-rubber surface were applied and measured by a force plate. Results and discussionHeight jumped was higher in the young, compared to the elderly volunteers (16.00±2.73 vs. 7.99±2.23% height; P<.001, respectively). The countermovement stiffness of the initial phase (P<.01) and the distance of the centre of pressures during static balance test was lower in the young group, compared to elderly (4.02±1.09 vs. 7.08±1.79cm2; P<.01, respectively). Moreover, the limits of the stability of the centre of pressures were higher in the elderly than in the young (168.50±32.26 vs. 32.70±37.54cm2; P<.01, respectively). No significant correlations were found between the strength and balance variables. In the elderly group, the countermovement descendent phase correlated with stiffness (r=–0.75; P<.05). ConclusionsAlthough countermovement descendent phase of the jump was reduced, the active elderly maintained sufficient strength levels that could prevent falls. We believe that reduced stiffness during countermovement jumps and better postural balance can be obtained by increasing functional range of movement in their lower extremities.

Body Composition, Somatotype and Physical Fitness of Young Soccer Players

PURPOSE: The aim of the study was to verify the body composition profile, somatotype and physical fitness of young soccer players by game position. METHODS: 23 male soccer players', under-20 years old, were evaluated. The somatotype was calculated using the anthropometric method and body composition was determined by bioelectric impedance. Physical fitness was assessed using tests for explosive strength of lower limbs, agility, velocity, abdominal endurance and aerobic fitness. RESULTS: Center backs and strikers are heavier and had more lean body mass (LBM) than midfield and running back players (67.7±2.0 kg and 65.4±3.4 kg vs. 60.0±1.9 kg and 58.4±3.7 kg, respectively) (p<.05). In addition, center backs are taller (187.7±3.2 cm) than all other players (goalkeepers, 178.0±6.5 cm; running back, 177.7±1.7 cm; midfield, 175.6±3.2 cm; strikers, 176.0±4.2 cm). Player's average somatotype was 2.6-3.7-3.3 (ectomorphic - mesomorphic). No differences were observed among game positions. Midfield and running back players were faster than the goalkeepers and center backs (6.92±0.33 sec and 6.82±0.20 sec vs. 7.48±0.44 sec and 7.35±0.20 sec, respectively) (p<.05) and there was no significant differences among the positions studied for the other physical fitness variables. CONCLUSIONS: The center backs and strikers presented higher scores in anthropometric variables; however, midfield and running back players are faster. The player's somatotype was ectomorphic - mesomorphic.

Physical Fitness Performance of Portuguese and Polish University Students

Physical fitness is an important component of health status and education. Concerns on physical fitness improvement were reported on health promotion programs, in particular regarding to childhood and youth. However, little attention has been taken to late adolescence and early adulthood, particularly to University students. PURPOSE: Evaluate and compare the performance level of muscular endurance, muscular strength and flexibility between Portuguese and Polish University students using physical fitness tests. METHODS: 81 students participated voluntarily, from which 36 (25 men and 11 women) were Portuguese (21.2 ± 1.2 y) and 45 (18 men and 27 women) were Polish (19.8 ± 0.5 y). The physical fitness performance between Portuguese and Polish groups was evaluated by the following tests: push-up, sit-up, standing long jump and toe-touch test. Mann-Whitney tests were used to detect differences in performance between groups in the physical fitness tests. RESULTS: Push-up scores were lower for both Portuguese and Polish groups, except for Portuguese females. This trend was particularly evident in Portuguese males (48%) and Polish females (70%). Significant differences (p<0.05) were found between women and men of same groups and between the same gender of different groups. A "poor or very poor" performance for standing long jump was found for Portuguese (86%) and Polish (78%) students, without significant differences between subjects of the same groups and different groups of the same gender. Significant differences (p<0.05) were found for Portuguese and Polish women for sit-up test. Portuguese (72%) and Polish (33%) females obtained the classification of "excellent or above average" in this test. The performance on toe-touch test was better in Polish students, but significant differences (p<0.05) were only found between Portuguese and Polish women. An "excellent or good" performance was found in 36% Portuguese and 78% Polish women. CONCLUSION: A lower upper body muscle strength (push-up) and lower limb explosive strength (long jump) was found for both Portuguese and Polish University students. Given that fitness condition may lead to serious health concerns, these results suggest that effective interventions are needed to improve the physical fitness on these University students.

The Yo–Yo intermittent recovery test in basketball players

The purpose of this study was to examine the physiological correlates of the Yo-Yo intermittent recovery test level 1 (Yo-Yo IR1) in basketball players. Twenty-two male basketball players (means+/-S.D., body mass 72.4+/-11.4kg, height 181.7+/-6.9cm, age 16.8+/-2.0 years) were tested for maximal oxygen uptake (VO(2max)), ventilatory threshold (VT) and running economy (RE) on a motorized treadmill. Lower limb explosive strength and anaerobic-capacity was assessed using vertical jumps (CMJ), 15m shuttle running sprint (15mSR) and line drill (LD), respectively. The same test battery was replicated after an experimental basketball game in order to assess selective effect of fatigue on physical performance. Pre to post-game CMJ (40.3+/-5.7 versus 39.9+/-5.9cm) and 15mSR (5.80+/-0.25 versus 5.77+/-0.22s) performances were not significantly different (p>0.05). LD performance decreased significantly post-game (from 26.7+/-1.3 to 27.7+/-2.7s, p<0.001). Yo-Yo IR1 performances (m) were significantly related to VO(2max) (r=0.77, p=0.0001), speed at VO(2max) (r=0.71, p=0.0001) and %VO(2max) at VT (r=-0.60, p=0.04). Yo-Yo IR1 performance was significantly correlated to post-game LD decrements (r=-0.52, p=0.02). These findings show that Yo-Yo IR1 may be considered as a valid basketball-specific test for the assessment of aerobic fitness and game-related endurance.

Aerobic Fitness and Yo-yo Continuous and Intermittent Tests Performances in Soccer Players: A Correlation Study

Yo-yo tests are very popular in soccer; however, no study has addressed details of their relation to canonical aspects of aerobic fitness. Furthermore, no information is available on the effect of the individual levels of lower limbs' explosive strength on yo-yo tests in soccer players. The purpose of this study was to examine the physiological determinants of Yo-yo Endurance Test Level 2 (YYETL2) and Yo-yo Intermittent Recovery Test Level 1 (YYIRTL1) in soccer players. Twenty-four soccer players (body mass, 74.6 +/- 8.5 kg; height, 178.1 +/- 4.5 cm; age, 25.6 +/- 5.1 years) were tested for VO2max and ventilatory threshold (VT) on a motorized treadmill. Lower-limb explosive strength was assessed using vertical countermovement jumps (CMJ) performed on a force platform. Results showed that YYETL2 and YYIRTL1 performances (m) were significantly related (r = 0.75, p = 0.00002). YYETL2 results were significantly related to VO2max, VTVO2, and speed at VT (r = 0.75, 0.76, and 0.83, respectively; p < 0.00002). Peak treadmill speed results were significantly related to YYETL2 and YYIRTL1 (r = 0.87 and 0.71, respectively; p < 0.0003). YYIRTL1 was related to CMJ peak power (r = 0.57; p = 0.003). These findings show that YYETL2 and YYIRTL1, although adopting similar starting and progression speeds, are influenced by different physiological variables. From these results, YYETL2 can be considered an aerobic fitness-related field test, whereas YYIRTL1 can be regarded as an aerobic-anaerobic, soccer-specific field test.

Estatuto posicional, força explosiva dos membros inferiores e velocidade imprimida à bola no remate em futebol. Um estudo com jovens praticantes do escalão sub-17

Positional Status, Explosive Strength and Ball Speed in Kicking Performance of Young Soccer Players. Of all the skills required to participate in Soccer, kicking and jumping have received great attention in different performance levels. The purpose of this study was to evaluate explosive strength of lower limbs and its relationship with ball speed, in young soccer players, according to their positional status. Thirty-one Portuguese players aged 16,52 ± 0,57 years and with an average of 8,26 ± 0,96 years of practice, participated in the study (4 goalkeepers, 9 fullbacks, 13 midfields and 5 forwards). A Stalker device (Professional Sports Radar) was used to assess ball speed during soccer kicking performance, and an Ergojump (Digitime 1000, Digitest Finland) was used to register the flight time in each vertical jump performed, in order to calculate the explosive strength of lower limbs. It was possible to verify that a positive correlation exists between explosive strength of lower limbs and ball speed (r = 0,10, p > 0.05 for the squat jump; r = 0,07, p > 0.05 for the countermovement jump). Forward players present higher explosive strength values and higher values in ball speed, when compared to other players, but we haven’t found statistical differences for any cases.