The purpose of this study was to identify alterations in preparatory muscle activation patterns across different drop heights in female athletes. Sixteen female high school volleyball players performed the drop vertical jump from three different drop heights. Surface electromyography of the quadriceps and hamstrings were collected during the movement trials. As the drop height increased, muscle activation of the quadriceps during preparatory phase also increased (p < .05). However, the hamstrings activation showed no similar increases relative to drop height. Female athletes appear to preferentially rely on increased quadriceps activation, without an increase in hamstrings activation, with increased plyometric intensity. The resultant decreased activation ratio of the hamstrings relative to quadriceps before landing may represent altered dynamic knee stability and may contribute to the increased risk of ACL injury in female athletes.
Kevin R. Ford, Gregory D. Myer, Laura C. Schmitt, Timothy L. Uhl and Timothy E. Hewett
Rodney Negrete and Jay Brophy
To determine (1) correlations between isokinetic lower extremity strength and functional performance and (2) correlations among different modes of isokinetic testing.
Design and Setting:
A correlational design with 6 measures. A series of strength, power, and agility tests was performed at a hospital-based outpatient physical therapy clinic.
A volunteer sample of 29 male and 31 female, college-age subjects participated.
All subjects were tested in the following isokinetic tests: reciprocal leg press, single-leg squat, and knee extension. Performance tests included single-leg hop and vertical jump and a speed/agility test.
Analysis showed isokinetic knee extension, leg press, and single-leg squat strength significantly correlated to all functional tests. There were significant correlations among the 3 different isokinetic strength measures, as well.
These results suggest a significant relationship between lower extremity open and closed chain isokinetic strength and functional performance testing.
Ronnie Lidor and Gal Ziv
The purpose of this article was to review a series of studies (n = 31) on physical characteristics, physiological attributes, and volleyball skills of female and male adolescent volleyball players. Among the main findings were (a) that male national players were taller and heavier than state and novice players, while female national players showed lower body fat values compared with state and novice players, and (b) vertical jump values were higher in starters versus nonstarters. Among the methodological concerns based on the reviewed studies were the lack of information on maturational age and lack of longitudinal studies. It was recommended that a careful selection of physiological tests should be made when assessing the abilities of adolescent volleyball players.
Rebecca A. Skillen, Massimo Testa, Elizabeth A. Applegate, Eric A. Heiden, Andrea J. Fascetti and Gretchen A. Casazza
This study examined the effect of amino acids in a carbohydrate beverage on cycling performance. Twelve male athletes (28.5 pp2.1 yr) cycled at 75% VO2peak for 90 min followed by a ride to exhaustion at 85% VO2peak, before (T1) and on 2 consecutive days (T2 and T3) after 2 weeks of supplementation with 3.6% carbohydrate plus 1% amino acids (AA) or 4.6% carbohydrate-only (CHO) isocaloric beverages. Muscle damage was assessed by plasma creatine kinase (CK), and muscle fatigue by changes in vertical jump pre- to postexercise. Muscle soreness, overall fatigue, and changes in mood state were assessed using questionnaires. Plasma CK was lower for AA in T3 (214.0 ss13.5 vs. 485.9 11191.4 U/L immediately post, 213.9 ÷ 13.1 vs. 492.0 ÷ 199.4 U/L 5 hr post, and 194.9 ÷ 17.9 vs. 405.9 ÷ 166.6 U/L 24 hr postexercise in AA and CHO, respectively). Time to exhaustion decreased from T2 to T3 only in CHO (10.9 ÷ 2.5 to 12.6 ÷ 3.2 vs. 13.8 ÷ 2.8 to 7.8 ÷ 1.5 min in AA and CHO, respectively). Vertical-jump change from pre- to postexercise was greater in T3 for the CHO treatment. Total fatigue score and mood disturbance decreased significantly only with AA in T3. The addition of AA to a carbohydrate beverage after consecutive-day exercise bouts reduced muscle damage as indicated by CK levels, decreased fatigue, and maintained exercise performance compared with consuming carbohydrate alone.
Julie A. Siegmund, Kellie C. Huxel and C. Buz Swanik
Determining whether there are compensations in those with jumper’s knee (JK) might further our understanding of the condition.
Comparing lower extremity kinematics and jump performance of basketball athletes with JK with those of healthy controls (C).
Repeated-measures control-match design.
24 male basketball players (12 JK, 12 C) matched by height, weight, position, experience, and frequency of play.
Standing countermovement and running layup jumps.
Main Outcome Measures:
Maximum vertical-jump height, footfall landing, and lower extremity sagittal-plane kinematics.
There were no significant group differences (P > .05) in vertical-jump height (JK = 64.3 ± 8.6 cm, C = 63.0 ± 9.8 cm) or layup height (JK = 71.3 ± 11.6 cm, C = 73.3 ± 11.0 cm). JK subjects landed flat footed (50%) more than controls (8%). JK subjects showed significantly more hip flexion (JK = 105° ± 24.8°, C = 89.8° ± 14.1°; P = .039) with decreased hip acceleration during the countermovement (JK = −3039 ± 1392°/s2, C = −4229 ± 1765°/s2; P = .040). When landing from the countermovement jump, JK subjects had significantly less knee acceleration (JK = −4960 ± 1512°/s2, C = −6736 ± 2009°/s2; P = 023) and in the layup showed significantly less ankle dorsiflexion (JK = 106.5° ± 9.0°, C = 112.5° ± 7.7°; P = .048) and hip acceleration (JK = − 2841 ± 1094°/s2, C = −3912 ± 1575°/s2; P = .033).
Compensatory strategies observed in JK subjects might help maintain performance, because their jump height was similar to that of healthy controls.
Oliver Gonzalo-Skok, Julio Tous-Fajardo, Carlos Valero-Campo, César Berzosa, Ana Vanessa Bataller, José Luis Arjol-Serrano, Gerard Moras and Alberto Mendez-Villanueva
To analyze the effects of 2 different eccentric-overload training (EOT) programs, using a rotational conical pulley, on functional performance in team-sport players. A traditional movement paradigm (ie, squat) including several sets of 1 bilateral and vertical movement was compared with a novel paradigm including a different exercise in each set of unilateral and multi-directional movements.
Forty-eight amateur or semiprofessional team-sport players were randomly assigned to an EOT program including either the same bilateral vertical (CBV, n = 24) movement (squat) or different unilateral multidirectional (VUMD, n = 24) movements. Training programs consisted of 6 sets of 1 exercise (CBV) or 1 set of 6 exercises (VUMD) × 6–10 repetitions with 3 min of passive recovery between sets and exercises, biweekly for 8 wk. Functional-performance assessment included several change-of-direction (COD) tests, a 25-m linear-sprint test, unilateral multidirectional jumping tests (ie, lateral, horizontal, and vertical), and a bilateral vertical-jump test.
Within-group analysis showed substantial improvements in all tests in both groups, with VUMD showing more robust adaptations in pooled COD tests and lateral/horizontal jumping, whereas the opposite occurred in CBV respecting linear sprinting and vertical jumping. Between-groups analyses showed substantially better results in lateral jumps (ES = 0.21), left-leg horizontal jump (ES = 0.35), and 10-m COD with right leg (ES = 0.42) in VUMD than in CBV. In contrast, left-leg countermovement jump (ES = 0.26) was possibly better in CBV than in VUMD.
Eight weeks of EOT induced substantial improvements in functional-performance tests, although the force-vector application may play a key role to develop different and specific functional adaptations.
Ivan Vrbik, Goran Sporiš, Lovro Štefan, Dejan Madić, Nebojša Trajković, Irena Valantine and Zoran Milanović
The number of familiarization sessions in fitness assessments seems to be critical and inconsistent. Therefore, the primary aim of this research was to determine the number of familiarization attempts that stabilize the results in particular physical fitness tests. The secondary aim was to establish the test reliability through familiarization sessions.
Thirty-nine primary school children participated in this research (age: 10.8 years, body mass: 40.6 ± 8.9 kg, and body height: 145.3 ± 7.2 cm). During six sessions, with one session every third day, participants performed the following tests to assess explosive strength (vertical jump and standing long jump), coordination (polygon backward and polygon with turn) and flexibility (toe touch).
The results of repeated analysis of variance (ANOVA) showed that there were significant increases (p < .05) in the polygon backward and polygon with turn performances from the first to third familiarization session. The standard error of measurement decreased as sessions progressed, indicating little within subject variation between the coordination test results following a familiarization period. Statistically significant differences were identified in the vertical jump test from the fourth test session compared with the first session. On the other hand, statistically significant differences for the standing long jump test were only found in the final session compared with the initial session. In the toe touch test, there were no significant increases from the first to the final familiarization session. All tests showed high a reliability coefficients, ranging from 0.979 to 0.991.
Polygon backward and polygon with turn performance may be a practical, reliable method to assess coordination in primary school-aged children. However, completion of at least 3 practice sessions is suggested for participants to obtain a stable score. In addition, both jump tests are feasible for assessing skill-related fitness in young children, although the scientific reliability of the two tests should be questioned and the tests should be tailored to fit the age group of the children.
Tyler J. Kirby, Jeffrey M. McBride, Tracie L. Haines and Andrea M. Dayne
The purpose of this investigation was to determine the relationship between relative net vertical impulse and jump height in a countermovement jump and static jump performed to varying squat depths. Ten college-aged males with 2 years of jumping experience participated in this investigation (age: 23.3 ± 1.5 years; height: 176.7 ± 4.5 cm; body mass: 84.4 ± 10.1 kg). Subjects performed a series of static jumps and countermovement jumps in a randomized fashion to a depth of 0.15, 0.30, 0.45, 0.60, and 0.75 m and a self-selected depth (static jump depth = 0.38 ± 0.08 m, countermovement jump depth = 0.49 ± 0.06 m). During the concentric phase of each jump, peak force, peak velocity, peak power, jump height, and net vertical impulse were recorded and analyzed. Net vertical impulse was divided by body mass to produce relative net vertical impulse. Increasing squat depth corresponded to a decrease in peak force and an increase in jump height and relative net vertical impulse for both static jump and countermovement jump. Across all depths, relative net vertical impulse was statistically significantly correlated to jump height in the static jump (r = .9337, p < .0001, power = 1.000) and countermovement jump (r = .925, p < .0001, power = 1.000). Across all depths, peak force was negatively correlated to jump height in the static jump (r = –0.3947, p = .0018, power = 0.8831) and countermovement jump (r = –0.4080, p = .0012, power = 0.9050). These results indicate that relative net vertical impulse can be used to assess vertical jump performance, regardless of initial squat depth, and that peak force may not be the best measure to assess vertical jump performance.
Dean G. Higham, David B. Pyne, Judith M. Anson and Anthony Eddy
Although the characteristics of 15-a-side rugby union players have been well defined, there is little information on rugby sevens players.
The authors profiled the anthropometric, physiological, and performance qualities of elite-level rugby sevens players and quantified relationships between these characteristics.
Eighteen male international rugby sevens players undertook anthropometric (body mass, height, sum of 7 skinfolds, lean-mass index), acceleration and speed (40-m sprint), muscle-power (vertical jump), repeatedsprint- ability (6 × 30-m sprint), and endurance (Yo-Yo Intermittent Recovery test and treadmill VO2max) testing. Associations between measurements were assessed by correlation analysis.
Rugby sevens players had anthropometric characteristics (body mass 89.7 ± 7.6 kg, height 1.83 ± 0.06 m, sum of 7 skinfolds 52.2 ± 11.5 mm; mean ± SD) similar to those of backs in international 15-player rugby union. Acceleration and speed (40-m sprint 5.11 ± 0.15 s), muscle-power (vertical jump 66 ± 7 cm), and endurance (VO2max 53.8 ± 3.4 mL · kg−1 · min−1 ) qualities were similar to, or better than, those of professional 15-a-side players. Coefficients of variation ranged from 2.5% to 22%. Relative VO2max was largely correlated with Yo-Yo distance (r = .60, .21−.82; 90% confidence interval) and moderately correlated with 40-m sprint time (r = −.46, −.75 to −.02) and repeated-sprint ability (r = −.38, −.72 to .09).
International rugby sevens players require highly developed speed, power, and endurance to tolerate the demands of competition. The small between-athletes variability of characteristics in rugby sevens players highlights the need for relatively uniform physical and performance standards in contrast with 15-a-side players.
Susumu S. Sawada, I-Min Lee, Hisashi Naito, Koji Tsukamoto, Takashi Muto and Steven N. Blair
Limited data are available on the relationship between muscular and performance fitness (MPF) and the incidence of type 2 diabetes.
A cohort of 3792 Japanese men completed a medical examination that included MPF and cardiorespiratory fitness tests. MPF index composite score was calculated using Z-scores from vertical jump, sit-ups, side step, and functional reach tests.
The mean follow-up period was 187 months (15.6 years). There were 240 patients who developed type 2 diabetes during follow-up. Relative risks and 95% confidence intervals (CI) for incidence of diabetes across baseline quartiles of MPF index composite score were obtained using the Cox proportional hazards model while adjusting for age, BMI, diastolic blood pressure, cigarette smoking, alcohol intake, and family history of diabetes. The relative risks for developing diabetes across quartiles of MPF index composite scores (lowest to highest) were 1.0 (referent), 1.15 (95% CI 0.83−1.60), 1.10 (0.78−1.55), and 0.57 (0.37−0.90) (P for trend = .061). These results were attenuated after adjustment for cardiorespiratory fitness (P for trend = .125).
This prospective study suggests that MPF is a predictor of type 2 diabetes, although its predictive ability was attenuated after adjusting for cardiorespiratory fitness.