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Biomedical subjects

J Garhammer

Publications and source records attributed to J Garhammer.

7 recordsLinked to original sources
PubMed2002

Effects of high-calorie supplements on body composition and muscular strength following resistance training.

BACKGROUND: Seventy-three healthy, male subjects randomly divided into 3 groups participated in a study to determine the effects of 2 high-calorie nutritional supplements on body composition, body segment circumferences, and muscular strength following a resistance-training (RT) program. METHODS: In addition to their normal diets group 1 (CHO/PRO; n=26) consumed a 8.4 Mj x day(-1) (2010 kcal) high calorie, high protein supplement containing 356 g carbohydrate and 106 g protein. Group 2 (CHO; n=25) consumed a carbohydrate supplement that was isocaloric with CHO/PRO. Group 3 (CTRL; n=22) received no supplement and served as a control. All subjects were placed on a 4-day x week(-1) RT program for 8 weeks. RESULTS: Dietary analysis revealed no significant differences in total energy consumption or nutrients at any time in the non-supplemented diets of the 3 groups. Significant (p= or <0.05) increases in body mass (BM) and fat-free mass (FFM) were observed in CHO/PRO and CHO compared to CTRL. Mean (+/- SD) increases in BM were 3.1+/-3.1 kg and 3.1+/-2.2 kg, respectively. Fat-free mass significantly (p= or <0.05) increased 2.9+/-3.4 kg in CHO/PRO and 3.4+/-2.5 kg in CHO. Muscular strength, as measured by a one-repetition maximum in the bench press, leg press, and lat-pull down increased significantly (p= or <0.05) in all groups. No significant differences in strength measures were observed among groups following training. CONCLUSIONS: Results indicate that high-calorie supplements are effective in increasing BM and FFM when combined with RT. However, once individual protein requirements are met, energy content of the diet has the largest effect on body composition.

Adolescent↗
PubMed1982

Energy flow during Olympic weight lifting.

Data obtained from 16-mm film of world caliber Olympic weight lifters performing at major competitions were analyzed to study energy changes during body segment and barbell movements, energy transfer to the barbell, and energy transfer between segments during the lifting movements contested. Determination of barbell and body segment kinematics and use of rigid-link modeling and energy flow techniques permitted the calculation of segment energy content and energy transfer between segments. Energy generation within and transfer to and from segments were determined at 0.04-s intervals by comparing mechanical energy changes of a segment with energy transfer at the joints, calculated from the scalar product of net joint force with absolute joint velocity, and the product of net joint torque due to muscular activity with absolute segment angular velocity. The results provided a detailed understanding of the magnitude and temporal input of energy from dominant muscle groups during a lift. This information also provided a means of quantifying lifting technique. Comparison of segment energy changes determined by the two methods were satisfactory but could likely be improved by employing more sophisticated data smoothing methods. The procedures used in this study could easily be applied to weight training and rehabilitative exercises to help determine their efficacy in producing desired results or to ergonomic situations where a more detailed understanding of the demands made on the body during lifting tasks would be useful.

Biomechanical Phenomena↗
PubMed1980

Power production by Olympic weightlifters.

A new procedure was developed for calculating power production during Olympic lifting movements and comparisons were made with a method previously used. The power output of seven superior lifters was determined during selected phases of the snatch, clean, and jerk, from films taken at the 1975 U.S. National Championships. The values obtained depended on the following variables: vertical change in the bar's mechanical energy from the beginning of a force exertion phase until maximum vertical bar velocity was achieved; work done by the athlete in producing horizontal bar movement; and work done in raising the body's center of gravity. Results showed the expected increase in power with increased bodyweight for a given movement. Values for the jerk drive ranged from 2140 watts in the 56 kg class to 4786 watts for a 110 kg lifter. Heavier lifters exceeded published maximal estimates for human power output during brief exertions. More significant was the high degree of consistency in the rate of work done by any given lifter in movements which were very similar with respect to joint action, but competitively had very different objectives. The procedure should prove useful in detecting problems in lifting movements that result in power outputs which are low relative to those measured for biomechanically equivalent exertions.

Biomechanical Phenomena↗
PubMed1980

Kinetic and kinematic factors involved in the execution of front aerial somersaults.

The purpose of this investigation was to study the variation in ground reaction forces during take-off and to calculate the angular impulse produced about the center of mass by these forces during execution of a front aerial somersault. Additionally, several kinematic variables were discussed in relation to performance. Nine high level female gymnasts volunteered as subjects. Ground reaction force (GRF) patterns were monitored by a Kistler force platform and the selected kinematic variables were calculated from high speed film synchronized with the force records. Total body center of mass position was determined and subsequently used in the calculation of angular impulse during rear, double, and front leg support. While results showed similar angular impulse patterns across our subject population, a variety of kinetic and kinematic variables were presented in order to more completely discuss the components of angular impulse development during the take-off phase of a front aerial somersault. For example, while the mean angular impulse was 61.7 Nms (+/- 13.1), a surprising finding was the contribution made to this impulse by the rear leg, 70.9% (+/- 7.2).

Adolescent↗
PubMed1979

Performance evaluation of Olympic weightlifters.

The comparison of weights lifted by athletes in different bodyweight categories is a continuing problem for the sport of olympic weightlifting. An objective mechanical evaluation procedure was developed using basic ideas from a model proposed by Ranta in 1975. This procedure was based on more realistic assumptions than the original model and considered both vertical and horizontal bar movements. Utilization of data obtained from film of national caliber lifters indicated that the proposed method was workable, and that the evaluative indices ranked lifters in reasonable order relative to other comparative techniques.

Biomechanical Phenomena↗
PubMed1977

Human patellar-tendon rupture.

The first biomechanical analysis of a human patellar-tendon rupture during actual sports competition is reported. Cinematographic data for analysis were collected at a national weight-lifting championship. Dynamic equations to mathematically model the lifter were developed to compute time course and magnitudes of hip, knee and ankle-joint moments of force and of tensile loading of the patellar tendon before and during tendon trauma. Results provided evidence that the range of maximum tensile stress of the tendon may be considerably greater during rapid dynamic loading conditions, as in many sports situations, than maximum tensile stress obtained during static test conditions.

Adult↗