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Russell R. Pate, Stewart G. Trost, Marsha Dowda, Alise E. Ott, Dianne S. Ward, Ruth Saunders and Gwen Felton

This study examined the tracking of selected measures of physical activity, inactivity, and fitness in a cohort of rural youth. Students (N = 181, 54.7% female, 63.5% African American) completed test batteries during their fifth- (age = 10.7 ± 0.7 years), sixth-, and seventh-grade years. The Previous Day Physical Activity Recall (PDPAR) was used to assess 30-min blocks of vigorous physical activity (VPA), moderate-to-vigorous physical activity (MVPA), TV watching and other sedentary activities, and estimated energy expenditure (EE). Fitness measures included the PWC 170 cycle ergometer test, strength tests, tnceps skinfold thickness, and BMI. Intraclass correlation coefficients (ICCs) for VPA, MVPA, and after-school EE ranged from 0.63 to 0.78. ICCs ranged from 0.49 to 0.71 for measures of inactivity and from 0.78 to 0.82 for the fitness measures. These results indicate that measures of physical activity, inactivity, and physical fitness tend to track during the transition from elementary to middle school.

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Myriam Guerra Balic, Eufemia Cuadrado Mateos, Carolina Geronimo Blasco and Bo Fernhall

The purpose was to compare physical fitness of two groups of adults with Down syndrome, one active group of Special Olympians (9 males, 4 females), and one sedentary group (5 males, and 2 females). The active group had trained for an average of 4.9 hr per week for a minimum of 1 year for Special Olympics competitions. Participants underwent laboratory testing, including (a) treadmill test to determine peak oxygen uptake; (b) isometric strength tests of handgrip, lower back, and quadriceps; (c) explosive power; and (d) body composition. Peak oxygen consumption and muscle strength were significantly greater in the active group. Although crossectional, these findings suggest that long term exercise training, at a greater than previously reported weekly training load, may enhance physical fitness in individuals with Down syndrome.

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Claire Peel, Carolyn Utsey and Jan MacGregor

This study aimed to evaluate the effects of an 8-week supervised exercise program on physiological measurements during treadmill walking, muscle strength, functional performance, and health status in older adults limited in physical function. Twenty-four participants were randomly assigned to an exercise group (EG, N = 13) or a control group (CG, N = 11), and were evaluated before and after the exercise program (EG) or 8-week period (CG). Evaluations included a progressive treadmill lest, strength testing, the Physical Performance Test (PPT), and the SF-36 Health Survey. The exercise program consisted of 3 sessions per week of brisk walking and strengthening exercises. The EG demonstrated increases in cardiorespiratory fitness and increases in treadmill walking time. The EG also demonstrated increases in force production in 3 of the 6 muscle groups that were tested. Both the EG and CG demonstrated improvements in PPT scores and in 2 health concepts on the SF-36 Health Survey.

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Koen A.P.M. Lemmink, Kemper Han, Mathieu H.G. de Greef, Piet Rispens and Martin Stevens

Several items of the Groningen Fitness Test for the Elderly (GFE) were tested. The GFE tests were administered twice, with 1 week between sessions. The participants were 458 independently living adults >55 years of age. For most tests, there was reasonable agreement between sessions, indicating absolute objectivity and stability, but results on the block-transfer test revealed a learning effect. Mean scores on the balance-board and sit-and-reach tests showed significant improvement, whereas grip-strength results deteriorated significantly. All tests satisfied the criteria for relative reliability. In conclusion, absolute and relative reliability of the tests of the GFE were satisfactory. If multiple applications of the GFE are planned for the same group of participants, 1 or more practice trials should be executed for the block-transfer test to avoid a learning effect. A standard warm-up protocol is recommended for the sit-and-reach test. Participants should be strongly encouraged to give a maximum effort on the strength tests.

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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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Andrew C. Fry, Carol C. Irwin, Justin X. Nicoll and David E. Ferebee

To determine absolute and relative (adjusted for body mass) strength, mean power, and mean velocity for upper and lower body resistance exercises, forty-seven young boys and girls participated in maximal strength testing. Healthy young boys and girls, ages 3- to 7-years old, were tested for one-repetition maximum (1-RM) strength, and 70% of 1-RM to determine mean power and mean velocity on the chest press and leg press exercises. Adult weight machines were modified to accommodate the smaller size and lower strength levels of the children. A 2 × 4 (sex × age) ANOVA was used to determine age and sex differences in performance. No interaction or sex differences were observed for any variable at any age. 1-RM strength, mean power, and mean velocity significantly increased across ages (p ≤ .05). When adjusted for body mass, the changes were insignificant, with one exception. Relative mean power for the bench press increased with age. Data indicated children from 3-7 years of age are capable of performing strength and power tests, but may require more attempts at maximal loads compared with adults. It appears that muscular strength and velocity during this stage of development are primarily dependent on increasing body mass, whereas power is influenced by additional variable(s).

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Gregory M. Gutierrez, Catherine Conte and Kristian Lightbourne

Head impacts are common in contact sports, but only recently has there been a rising awareness of the effects of subconcussive impacts in adolescent athletes. A better understanding of how to attenuate head impacts is needed and therefore, this study investigated the relationship between neck strength, impact, and neurocognitive function in an acute bout of soccer heading in a sample of female high school varsity soccer players. Seventeen participants completed the ImPACT neurocognitive test and had their isometric neck strength tested (flexion, extension, and bilateral flexion) before heading drills. Each participant was outfitted with custom headgear with timing switches and a three-dimensional accelerometer affixed to the back of the head, which allowed for measurement of impact during heading. Participants performed a series of 15 directional headers, including 5 forward, 5 left and 5 right headers in a random order, then completed the ImPACT test again. Neurocognitive tests revealed no significant changes following heading. However, there were statistically significant, moderate, negative correlations (r = −0.500:−0.757, p < .05) between neck strength and resultant header acceleration, indicating that those with weaker necks sustained greater impacts. This suggests neck strengthening may be an important component of any head injury prevention/reduction program.

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Kristian M. O’Connor, Carl Johnson and Lauren C. Benson

The function of the hamstrings in protecting the ACL is not fully understood. The purpose of this study was to determine how landing knee mechanics were affected by hamstrings fatigue, analyzed with principal components analysis (PCA). Knee joint mechanics were collected during single-leg stride landings that were followed by lateral and vertical jumps. An isokinetic fatigue protocol was employed to reduce hamstrings strength by 75% at the cessation of the exercise protocol. On the landing test day, participants performed the stride landing maneuvers before and after the fatigue protocol. PCA was performed on the landing knee joint angle, moment, and power waveforms, and MANOVAs were conducted on the retained PCs of each waveform (P < .05). On the strength test day, hamstrings strength recovery was assessed with an identical fatigue protocol followed by strength assessment ~75 s after the cessation of exercise. Pre- and postexercise hamstrings strength on this day was assessed with a dependent t test (P < .05). The hamstrings strength remained significantly reduced by ~8% postexercise (75 s). For stride landings followed by vertical jumps, there were significantly reduced knee flexion angles, extensor moments, and energy absorption. This was indicative of a stiffer landing strategy postfatigue, which has been associated with increased ACL loading.

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Christopher A. Bailey, Kimitake Sato, Angus Burnett and Michael H. Stone

The purpose of this investigation was to determine the existence of bilateral strength and force-production asymmetry and evaluate possible differences based on sex, as well as strength level. Asymmetry was assessed during weight-distribution (WtD) testing, unloaded and lightly loaded static- (SJ) and countermovement-jump (CMJ) testing, and isometric midthigh-pull (IMTP) strength testing. Subjects included 63 athletes (31 male, 32 female) for WtD, SJ, and CMJ tests, while 129 athletes (64 male, 65 female) participated in IMTP testing. Independent-samples t tests were used to determine possible differences in asymmetry magnitude between males and females, as well as between strong and weak athletes. Cohen d effect-size (ES) estimates were also used to estimate difference magnitudes. Statistically different asymmetry levels with moderate to strong ESs were seen between males and females in WtD, 0-kg SJ (peak force [PF]), 20-kg SJ (peak power [PP]), 0-kg CMJ (PF, PP, net impulse), and 20-kg CMJ (PF), but no statistical differences were observed in IMTP variables. Dividing the sample into strong and weak groups produced statistically significant differences with strong ES estimates in IMTP PF and rate of force development, and many ESs in jump symmetry variables increased. The results of this investigation indicate that females may be more prone to producing forces asymmetrically than males during WtD and jumping tasks. Similarly, weaker athletes displayed more asymmetry than stronger athletes. This may indicate that absolute strength may play a larger role in influencing asymmetry magnitude than sex.

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Irineu Loturco, Lucas A. Pereira, Ciro Winckler, Weverton L. Santos, Ronaldo Kobal and Michael McGuigan

Purpose: To examine the relationships between different loading intensities and movement velocities in the bench-press exercise (BP) in Paralympic powerlifters. Methods: A total of 17 national Paralympic powerlifters performed maximum dynamic strength tests to determine their BP 1-repetition maximum (1RM) in a Smith-machine device. A linear position transducer was used to measure movement velocity over a comprehensive range of loads. Linear-regression analysis was performed to establish the relationships between the different bar velocities and the distinct percentages of 1RM. Results: Overall, the correlations between bar velocities and %1RM were strong over the entire range of loads (R 2 .80–.91), but the precision of the predictive equations (expressed as mean differences [%] between actual and predicted 1RM values) were higher at heavier loading intensities (∼20% for loads ≤70% 1RM and ∼5% for loads ≥70% 1RM). In addition, it seems that these very strong athletes (eg, 1RM relative in the BP = 2.22 [0.36] kg·kg−1, for male participants) perform BP 1RM assessments at lower velocities than those previously reported in the literature. Conclusions: The load–velocity relationship was strong and consistent in Paralympic powerlifters, especially at higher loads (≥70% 1RM). Therefore, Paralympic coaches can use the predictive equations and the reference values provided here to determine and monitor the BP loading intensity in national Paralympic powerlifters.