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Christie Tangalos, Samuel J. Robertson, Michael Spittle and Paul B. Gastin

Context:

Player match statistics in junior Australian football (AF) are not well documented, and contributors to success are poorly understood. A clearer understanding of the relationships between fitness and skill in younger players participating at the foundation level of the performance pathway in AF has implications for the development of coaching priorities (eg, physical or technical).

Purpose:

To investigate the relationships between indices of fitness (speed, power, and endurance) and skill (coach rating) on player performance (disposals and effective disposals) in junior AF.

Methods:

Junior male AF players (N = 156, 10–15 y old) were recruited from 12 teams of a single amateur recreational AF club located in metropolitan Victoria. All players were tested for fitness (20-m sprint, vertical jump, 20-m shuttle run) and rated by their coach on a 6-point Likert scale for skill (within a team in comparison with their teammates). Player performance was assessed during a single match in which disposals and their effectiveness were coded from a video recording.

Results:

Coach rating of skill displayed the strongest correlations and, combined with 20-m shuttle test, showed a good ability to predict the number of both disposals and effective disposals. None of the skill or fitness attributes adequately explained the percentage of effective disposals. The influence of team did not meaningfully contribute to the performance of any of the models.

Conclusions:

Skill development should be considered a high priority by coaches in junior AF.

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Stephen J. Kinzey, Mitchell L. Cordova, Kevin J. Gallen, Jason C. Smith and Justin B. Moore

Objective:

To determine whether a standard 20-min ice-bath (10°C) immersion of the leg alters vertical ground-reaction-force components during a 1 -legged vertical jump.

Design:

A 1 × 5 factorial repeated-measures model was used.

Setting:

The Applied Biomechanics Laboratory at The University of Mississippi.

Participants:

Fifteen healthy and physically active subjects (age = 22.3 ± 2.1 years, height = 177.3 ± 12.2 cm, mass = 76.3 ± 19.1 kg) participated.

Intervention:

Subjects performed 25 one-legged vertical jumps with their preferred extremity before (5 jumps) and after (20 jumps) a 20-min cold whirlpool to the leg. The 25 jumps were reduced into 5 sets of average trials.

Main Outcome Measures:

Normalized peak and average vertical ground-reaction forces, as well as vertical impulse obtained using an instrumented force platform.

Results:

Immediately after cryotherapy (sets 2 and 3), vertical impulse decreased (P = .01); peak vertical ground-reaction force increased (set 2) but then decreased toward baseline measures (P= .02). Average vertical ground-reaction force remained unchanged (P >.05).

Conclusions:

The authors advocate waiting approximately 15 min before engaging in activities that require the production of weight-bearing explosive strength or power.

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Joanne E. Richards, Timothy R. Ackland and Bruce C. Elliott

Thirty-seven females, aged initially between 10 and 13.5 years, completed a mixed longitudinal study over 3.3 years to investigate the effect of training volume and growth upon gymnastic performance. Gymnasts undergoing high volume training (mean = 30 hrs/week: Group 1) and moderate volume training (mean = 15 hrs/week: Group 2) were tested at 4-month intervals on growth measures including height, mass, skinfolds, and segment lengths, as well as the strength of lower limb, upper limb, and trunk musculature. Functional gymnastic development was observed through the assessment of generic, whole body rotation tasks, a vertical jump, and a v-sit action. The high training volume gymnasts were significantly smaller but markedly stronger than those gymnasts in Group 2 despite the size disadvantage. Consequently, Group 1 gymnasts were able to produce higher velocities for front and backward rotations and a faster v-sit action. These training group differences remained significant after initial size differences were taken into account via an analysis of covariance.

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Andrew C. Fry, William J. Kraemer, Michael H. Stone, Beverly J. Warren, Jay T. Kearney, Carl M. Maresh, Cheryl A. Weseman and Steven J. Fleck

To examine the effects of 1 week of high volume weightlifting and amino acid supplementation, 28 elite junior male weightlifting received either amino acid (protein) or lactose (placebo) capsules using double-blind procedures. weightlifting test sessions were performed before and after 7 days of high volume training sessions. Serum concentrations of testosterone (Tes), cortisol (Cort), and growth hormone (GH) as well as whole blood iactate (HLa) were determined from blood draws. Lifting performance was not altered for either group after training, although vertical jump performance decreased for both groups. Both tests elicited significantly elevated exercise-induced hormonal and HLa concentrations. Significant decreases in postexercise hormonal and HLa concentrations from Test 1 to Test 2 were observed for both groups. Tes concentrations at 7 a.m. and preexercise decreased for both groups from Test 1 to Test 2, while the placebo group exhibited a decreased 7 a.m. Tes/ Cort. These data suggest that amino acid supplementation does not influence resting or exercise-induced hormonal responses to 1 week of high volume weight training, but endocrine responses did suggest an impending overtraining syndrome.

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Khalid S. Almuzaini

The main purpose of the present study was to determine isokinetic strength and endurance, isometric strength, and anaerobic power for untrained healthy Saudi children and adolescents. The secondary purpose was to evaluate the effects of age in relation to anthropometric characteristics on strength and anaerobic performances. Forty-four (untrained) 11- to 19-year-old boys were grouped by age: 11-13 years, 14–16 years, and 17–19 years. All participants underwent anthropometric measurements, a flexibility test, a vertical jump test, a grip strength test, isokinetic strength measurements (Cybex Norm), and a Wingate anaerobic power test. Oneway ANOVA results indicated age-related increases in muscle strength and power. High correlation coefficients that were found among age and strength and anaerobic power indices almost disappeared when fat-free mass (FFM) was controlled for, indicating that the amount of variance in these indices that was explained by age is mostly shared by FFM. In addition, stepwise linear regression models indicated that FFM was the main predictor of strength and power performances. Thus, FFM was the best scaling variable for body size when comparing these age groups of Saudis. Until wide-range normal representative values for isokinetic strength and anaerobic power for Saudi children and adolescents are available, the present study’s results can serve as a reference for these indices.

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Konstantinos Tambalis, Demosthenes Panagiotakos, Giannis Arnaoutis and Labros Sidossis

We aimed to model endurance, explosive power, and muscle strength in relation to body mass index (BMI) and physical-fitness tests in Greek children aged 7–10 years old. In the present large epidemiological study, anthropometric measurements and physical-fitness tests (i.e., multistage shuttle run, vertical jump, standing long jump, small ball throw and 30-m sprint) from 141,169 children were analyzed. Age- and sex-specific normative values for physical fitness tests were expressed as tabulated percentiles using the LMS statistical method. The correlation coefficients between BMI and performances were negative and significant for both sexes (p < .01) in all physical-fitness tests. The only exception was a positive correlation between ball throw and BMI (p < .01). Only 2.9% and 4.0% of boys and girls respectively, passed the upper quartiles in all tests. The performance in speed may serve as a predictive factor explaining, at least in part, the performance in aerobic endurance and explosive power in children aged 7–10 years. The presented population-based data for physical-fitness tests revealed that only a small percentage of these children are in the upper quartiles in all tests. Furthermore, the data suggests that speed performance can be used to predict physical fitness.

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Avery D. Faigenbaum, Leonard D. Zaichkowsky, Wayne L. Westcott, Lyle J. Micheli and Allan F. Fehlandt

The effectiveness of a twice-a-week strength training program on children was evaluated in 14 boys and girls (mean age 10.8 yrs) who participated in a biweekly training program for 8 weeks. Each subject performed three sets of 10 to 15 repetitions on five exercises with intensities ranging between 50 and 100% of a given 10-repetition maximum (RM). All subjects were pre- and posttested on the following measures: 10-RM strength, sit and reach flexibility, vertical jump, seated ball put, resting blood pressure, and body composition parameters. The subjects were compared to a similar group of boys and girls (n = 9; mean age 9.9 yrs) who were randomly selected to serve as controls. Following the training period, the experimental group made greater gains in strength (74.3%) as compared to the control group (13.0%) (p < 0.001), and differences in the sum of seven skinfolds were noted (−2.3% vs. +1.7%, respectively, p < 0.05). Training did not significantly affect other variables. These results suggest that participation in a short-term, twice-a-week strength training program can increase the strength and improve the body composition of young boys and girls.

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Susumu S. Sawada, I-Min Lee, Hisashi Naito, Koji Tsukamoto, Takashi Muto and Steven N. Blair

Background:

Limited data are available on the relationship between muscular and performance fitness (MPF) and the incidence of type 2 diabetes.

Methods:

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.

Results:

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).

Conclusions:

This prospective study suggests that MPF is a predictor of type 2 diabetes, although its predictive ability was attenuated after adjusting for cardiorespiratory fitness.

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Gaston Beunen, Martine Thomis, Maarten Peeters, Hermine H. Maes, Albrecht L. Claessens and Robert Vlietinck

The aim of this study is to quantify the genetic and environmental variation in isometric and explosive strength (power) in children and adolescents, using structural equation models. Arm pull (static strength) and vertical jump (explosive strength, power) were measured in 105 twin pairs from the Leuven Longitudinal Twin Study. Boys and girls were tested at annual intervals between 10 and 16 years and at 18 years. Path models were fitted to the observed strength characteristics and a gender heterogeneity analysis was performed at each age level. A model including additive genetic and specific environmental factors (AE-model) allowing for a difference in total phenotypic variance or in genetic/environmental variance components in boys and girls best explains both strength characteristics at most age levels. The additive genetic contribution for isometric strength varies between a2 = .44 and a2 = .83, and for explosive strength between a2 = .47 and a2 = .92, except at 16 years in males. In conclusion there is good evidence that during the growth period both static and explosive strength are under moderate to moderately strong genetic influence.

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Michael H. Stone, Kimberly Sanborn, Lucille L. Smith, Harold S. O'Bryant, Tommy Hoke, Alan C. Utter, Robert L. Johnson, Rhonda Boros, Joseph Hruby, Kyle C. Pierce, Margaret E. Stone and Brindley Garner

The purpose of this investigation was to study the efficacy of two dietary supplements on measures of body mass, body composition, and performance in 42 American football players. Group CM (n = 9) received creatine monohy-drate, Group P (n = 11) received calcium pyruvate. Group COM (n = 11) received a combination of calcium pyruvate (60%) and creatine (40%), and Group PL received a placebo. Tests were performed before (Tl) and after (T2) the 5-week supplementation period, during which the subjects continued their normal training schedules. Compared to P and PL. CM and COM showed significantly greater increases for body mass, lean body mass, 1 repetition maximum (RM) bench press, combined 1 RM squat and bench press, and static vertical jump (SVJ) power output. Peak rate of force development for SVJ was significantly greater for CM compared to P and PL. Creatine and the combination supplement enhanced training adaptations associated with body mass/composition, maximum strength, and SVJ; however, pyruvate supplementation alone was ineffective.