Biomedical subjects

Jay R Hoffman

Publications and source records attributed to Jay R Hoffman.

24 records · Page 2Linked to original sources

PubMed2003

Comparison between linear and nonlinear in-season training programs in freshman football players.

The purpose of this study was to compare linear (LT) with nonlinear (NL) in-season training programs in freshman football players during the course of 2 separate seasons. During the first year (n = 14, mean +/- SD = 177.3 +/- 4.8 cm, 88.0 +/- 9.7 kg), the LT program was employed 2 days per week. In the second year (n = 14, 175.0 +/- 7.1 cm, 94.2 +/- 20.5 kg), a 2 days per week LT was used. Subjects were tested for maximal strength in the squat (1 repetition maximum [1RM]) and bench press (1RM) exercises. A significant improvement in 1RM squat was seen in LT, but not in NL. No significant improvement in 1RM bench press was seen in either group. A significant difference between LT and NL was observed in Delta1RM squat (13.8 +/- 7.4 kg compared with 1.6 +/- 2.6 kg, respectively). Results of this study suggest that LT may be more effective in eliciting strength gains than NL in freshman football players during an in-season training program.

Adolescent↗

PubMed2002

Physiological and biomechanical analysis of treadmill walking up various gradients in men and women.

This investigation was undertaken to examine the physiological and biomechanical responses during treadmill walking up various gradients in men and women. Groups of 11 men and 11 women took part in four experiments consisting of 8 min treadmill walks at 1.3 m.(-1) up gradients of 0%, 5%, 10% and 15%. The subjects also underwent an anthropometric assessment during which their height, body mass (BM), percentage (%) body fat, lean body mass (LBM), and waist-to-hip ratio (WHR) were obtained. During exercise, each subject was videotaped during three walking cycles so that sagittal kinematics including stride length (SL) and frequency (SF) and ranges of motion achieved at the shoulder, hip and knee during a walking cycle could be determined using a motion analysis system. The motion capture was followed by a measurement of steady-state oxygen uptake (VO(2)) and heart rate (HR) using indirect calorimetry and a HR monitor. Compared to men, women were higher in % body fat, but lower in height, BM, LBM, and WHR. The VO(2) in millilitres per kilogram per minute and HR were similar between men and women at 0% and 5%, but greater in women than men at 10% and 15%. The SL and SF were greater and smaller, respectively, in men than women up all gradients. Shoulder extension was greater up gradients of 10% and 15% in women than men, whereas no sex difference in shoulder flexion was noted. Hip extension and flexion as well as knee flexion remained the same between men and women up all gradients. An inverse relationship was observed between VO(2) in millilitres per kilogram per minute and BM, LBM, and WHR when men and women were combined. In conclusion, the mass-specific metabolic cost of treadmill walking up high gradients is greater in women than men. Such an increase in relative metabolic cost may be attributable to the fact that women are smaller in size, and/or have relatively more BM distributed peripherally. This sex difference may also be due to a greater movement of the upper limbs in women during walking uphill, although direct evidence is needed to support this contention.

Adult↗

PubMed2002

American College of Sports Medicine position stand. Progression models in resistance training for healthy adults.

In order to stimulate further adaptation toward a specific training goal(s), progression in the type of resistance training protocol used is necessary. The optimal characteristics of strength-specific programs include the use of both concentric and eccentric muscle actions and the performance of both single- and multiple-joint exercises. It is also recommended that the strength program sequence exercises to optimize the quality of the exercise intensity (large before small muscle group exercises, multiple-joint exercises before single-joint exercises, and higher intensity before lower intensity exercises). For initial resistances, it is recommended that loads corresponding to 8-12 repetition maximum (RM) be used in novice training. For intermediate to advanced training, it is recommended that individuals use a wider loading range, from 1-12 RM in a periodized fashion, with eventual emphasis on heavy loading (1-6 RM) using at least 3-min rest periods between sets performed at a moderate contraction velocity (1-2 s concentric, 1-2 s eccentric). When training at a specific RM load, it is recommended that 2-10% increase in load be applied when the individual can perform the current workload for one to two repetitions over the desired number. The recommendation for training frequency is 2-3 d x wk(-1) for novice and intermediate training and 4-5 d x wk(-1) for advanced training. Similar program designs are recommended for hypertrophy training with respect to exercise selection and frequency. For loading, it is recommended that loads corresponding to 1-12 RM be used in periodized fashion, with emphasis on the 6-12 RM zone using 1- to 2-min rest periods between sets at a moderate velocity. Higher volume, multiple-set programs are recommended for maximizing hypertrophy. Progression in power training entails two general loading strategies: 1) strength training, and 2) use of light loads (30-60% of 1 RM) performed at a fast contraction velocity with 2-3 min of rest between sets for multiple sets per exercise. It is also recommended that emphasis be placed on multiple-joint exercises, especially those involving the total body. For local muscular endurance training, it is recommended that light to moderate loads (40-60% of 1 RM) be performed for high repetitions (> 15) using short rest periods (< 90 s). In the interpretation of this position stand, as with prior ones, the recommendations should be viewed in context of the individual's target goals, physical capacity, and training status.

Adaptation, Physiological↗

PubMed2002

Performance, biochemical, and endocrine changes during a competitive football game.

PURPOSE: This study represents the first time that anaerobic power performance was examined during an actual intercollegiate American football game. In addition, biochemical and endocrine responses also were examined to assess the physiological stress imposed by this competitive contest. METHODS: Twenty-one members of a NCAA Division III football team were divided into two groups. Group one (ST) were starters (N = 11). The second group (RS) consisted of red-shirt players (N = 10). Blood samples were obtained 24 h (Pre1) and 2.5 h (Pre2) before the game and within 15 min of game conclusion (IP). Anaerobic power measures were recorded approximately 10 min before kickoff (pre) and following the first (Q1), second (Q2), third (Q3), and fourth (Q4) quarters. RESULTS: Peak force (PF) and power (PP) in both squat and countermovement jumps decreased (P < 0.05) from pre to Q2 in both ST and RS; however, all variables returned to baseline levels by Q4. When averaged across trials, PF and PP in both jumps were greater (P < 0.05) in ST than RS. No significant changes in testosterone concentrations with respect to time or between groups were seen. Cortisol concentrations were significantly higher for ST at IP than RS. No significant changes in creatine kinase, alanine aminotransferase, urea, or uric acid were observed in either group from Pre2 to IP. In addition, no between group differences were seen in these variables. Myoglobin and aspartate aminotransferase significantly increased from Pre2 to IP in ST, and a significant difference in myoglobin concentrations was seen between the groups at IP. CONCLUSIONS: Performance, biochemical, and endocrine changes in these NCAA Division III football players reflected the stress and muscle damage that occurs as a result of a competitive American football game.

Adult↗

PubMed2002

Evaluation of a new anaerobic power testing system.

The purpose of this study was to evaluate the reliability of a new anaerobic athletic performance system. This system is proposed to assess vertical jump height, anaerobic power through repetitive jumping, and reaction to both an auditory and visual stimulus. One hundred twenty-three subjects (92 men and 31 women; mean +/- SD: age, 20.5 +/- 2.1 years; body weight, 83.1 +/- 20.4 kg; height, 176.0 +/- 9.2 cm) volunteered to participate. To assess reliability of the new testing device, subjects were tested on 3 separate occasions (T1, T2, and T3). At least 72 hours but not more than 1 week separated each laboratory visit. During each testing session subjects performed a countermovement jump (CMJ), a 30 consecutive jumps anaerobic power test (30JT), and reaction to both an auditory and visual stimulus. Results showed no differences between T1, T2, and T3 in either CMJ height or 30JT assessments. However, reaction to an audible or visual stimulus significantly improved during each testing session. Intraclass reliability of the CMJ and the 30JT was greater than 0.96 across the 3 trials. Pearson correlation coefficients of r > 0.90 were seen for the CMJ and 30JT, indicating a high test-retest reliability. The test-retest reliability for the reaction tests were lower (r ranging from 0.72 to 0.83). A Bland-Altman plot showed limited agreement between methods of vertical jump height assessment. Results indicate that this new testing device shows high reliability to assess both CMJ height and anaerobic power. In addition, anaerobic power assessment in a jump test provides a specific measure of anaerobic power for many sports incorporating similar performance patterns.

Adolescent↗

PubMedDate not supplied

Recreational sports participation is associated with enhanced physical fitness in children.

The purpose of this study was to examine the association between seasonal participation in recreational sports and its influence on physical fitness measures in children. A total of 44 children (20 boys and 24 girls) all in the fifth grade (11.2 +/- 0.3 yr) were tested for flexibility, upper body strength, upper body power, and lower body power. Activity questionnaires examined seasonal participation rates in recreational sports. Spearman rank correlations showed significant correlations between sport participation rates and performance on selected physical fitness tests (p range between 0.34 and 0.55). Subjects participating in recreational sport programs throughout the year (fall, winter, and spring) performed significantly better in tests of upper body strength, upper body power, and lower body power than subjects who did not participate in any sport or subjects who participated in only one sport. These findings suggest that regular participation in recreational sports throughout the year may be associated with higher levels of muscular strength and anaerobic power in children.

Anaerobic Threshold↗