William J. Kraemer and Nicholas A. Ratamess
Andrew C. Fry, Dawn R. Powell and William J. Kraemer
Although it is generally accepted that human performance must be assessed in a manner specific to the training, previous studies have violated this principle. In order to determine the validity of evaluating short-term resistance training programs with isometric and isokinetic measures, 23 recreationally active males participated in an 8-week training program. Subjects were randomly divided into barbell squat, hip sled, leg extension, and control groups. Pre- and posttesting of quadriceps strength was performed with a Cybex isokinetic dynamometer. Six angle-specific torques (N.m) were determined at 0 rad-s-1 and 1.05 rad-s-1. Ten RM training loads increased significantly for all groups that trained. Isometric torque values differed significantly from isokinetic torque values at 30, 60, 75, and 90° of leg flexion for all groups. No significant torque increases from pre- to posttest were observed for any group at any limb angle for either isometric or isokinetic testing, or for isokinetic peak torque. This indicates that strength increases during short-term dynamic external resistance exercise are not adequately assessed with either isometric or isokinetic evaluations.
Semyon Slobounov, William Kraemer, Wayne Sebastianelli, Robert Simon and Shannon Poole
The primary purpose of this paper was to demonstrate how modem motion tracking technologies, i.e., the Hock of Birds, and computer visualization graphics may be used in a clinical setting. The idea that joint injury reduces proprioception was investigated, and data for injured subjects were compared to data for noninjured subjects (subjects in all experiments were college students). Two experiments showed that there were no significant losses in joint position sense in knee-injured subjects, and both injured and noninjured groups visually overestimated knee movements. However, injured subjects showed no significant differences when visual reproduction data were compared with actual movement data. In addition, these data indicated that injured subjects may have greater potential for apprehension than noninjured subjects, at least in terms of visual estimation of movement ranges. This is an idea that needs further testing.
Simon Walker, Fabrizio Santolamazza, William Kraemer and Keijo Häkkinen
The present study investigated changes in acute serum hormone responses to a resistance exercise bout following a prolonged period of hypertrophic resistance training in young (YM) and older men (OM). Subjects performed a 5 × 10RM leg press exercise protocol before and after 20 weeks of hypertrophic resistance training. In YM, the acute responses in growth hormone were greater compared with before training (p < .05), and cortisol concentration did not increase after training. Endocrine responses in OM were similar before and after training. Greater acute growth hormone responses after training were associated with larger gains in lean mass in the entire subject group (r = .596, p = .019). These findings suggest that, in general, YM demonstrate greater adaptability within the endocrine system compared with OM. However, adaptability in growth hormone response was associated with larger training-induced gains independent of age.
Andrew C. Fry, William J. Kraemer, James M. Lynch and Jason M. Barnes
To report a joint-centered mechanism of performance decrements caused by overtraining.
Eleven weight-trained men, 1 (subject A) with overload injury of the knees.
High-intensity squat resistance-exercise overtraining for 2 weeks.
1RM lower-body strength, isokinetic and isometric knee-extension strength, and stimulated isometric knee-extension strength.
Subject A’s 1RM strength decreased 40.3 kg, and the other overtrained subjects (OT) exhibited significant (P < .05) 1RM decrements (x = –9.3 kg). Isokinetic knee-extension strength decreased for all subjects. For the OT group, voluntary isometric knee-extension strength did not change and stimulated isometric knee-extension strength decreased. Subject A exhibited increased values for both these variables.
These data indicate that muscle strength was attenuated for subject A only during dynamic activity. It is theorized that subject A exhibited a joint-centered overtraining syndrome, with afferent inhibition from the affected joints impairing dynamic strength.
William J. Kraemer, Andrew C. Fry, Peter N. Frykman, Brian Conroy and Jay Hoffman
The use of resistance training for children has increased in popularity and interest. It appears that children are capable of voluntary strength gains. Exercise prescription in younger populations is critical and requires certain program variables to be altered from adult perspectives. Individualization is vital, as the rate of physiological maturation has an impact on the adaptations that occur. The major difference in programs for children is the use of lighter loads (i.e., > 6 RM loads). It appears that longer duration programs (i.e., 10-20 wks) are better for observing training adaptations. This may be due to the fact that it takes more exercise to stimulate adaptational mechanisms related to strength performance beyond that of normal growth rates. The risk of injury appears low during participation in a resistance training program, and this risk is minimized with proper supervision and instruction. Furthermore, with the incidence of injury in youth sports, participation in a resistance training program may provide a protective advantage in one’s preparation for sports participation.
Robert U. Newton, William J. Kraemer, Keijo Häkkinen, Brendan J. Humphries and Aron J. Murphy
The aim of this study was to investigate the kinematics, kinetics, and neural activation of the traditional bench press movement performed explosively and the explosive bench throw in which the barbell was projected from the hands. Seventeen male subjects completed three trials with a bar weight of 45% of the subject's previously determined 1RM. Performance was significantly higher during the throw movement compared to the press for average velocity, peak velocity, average force, average power, and peak power. Average muscle activity during the concentric phase for pectoralis major, anterior deltoid, triceps brachii, and biceps brachii was higher for the throw condition. It was concluded that performing traditional press movements rapidly with light loads does not create ideal loading conditions for the neuromuscular system with regard to explosive strength production, especially in the final stages of the movement, because ballistic weight loading conditions where the resistance was accelerated throughout the movement resulted in a greater velocity of movement, force output, and EMG activity.
Janne Sallinen, Arto Pakarinen, Mikael Fogelholm, Elina Sillanpää, Markku Alen, Jeff S. Volek, William J. Kraemer and Keijo Häkkinen
This study examined the effects of strength training and diet on serum basal hormone concentrations and muscle mass in aging women. Fifty-one women age 49 to 74 y were divided into two groups: strength training and nutritional counseling (n = 25), and strength training (n = 26). Both groups performed strength training twice a week for 21 wk. Nutritional counseling was given to attain sufficient energy and protein intake and recommended intake of fat and fiber. We found that the cross-sectional area of the quadriceps femoris increased by 9.5 ± 4.1% in the nutritional counseling group versus 6.8 ± 3.5% in the strength training only group after training (P < 0.052). Nutritional counseling evoked dietary changes such as increases in the proportion of energy from protein and the ratio of poly-unsaturated and saturated fatty acids. Strength training increased testosterone and testosterone/sex hormone-binding globulin ratio after the first half of training, but these returned to baseline values at the end of the entire training period. Changes in serum basal hormone concentrations did not differ between the groups. Our results support the conclusion that nutritional counseling can contribute to the increase in the muscle cross-sectional area during prolonged strength training in aging women.
Semyon M. Slobounov, Shannon T. Poole, Robert F. Simon, Elena S. Slobounov, Jill A. Bush, Wayne Sebastianelli and William Kraemer
Assessment and enhancement of joint position sense is an inexact science at best. Anew method of evaluating and improving this sense using motion-tracking technology that incorporates computer visualization graphics was examined. Injured and healthy subjects were evaluated for their abilities to determine shoulder joint position, after abduction, in two tasks. The first was active reproduction of a passively placed angle. The second was visual reproduction of such an angle. A training protocol was added to determine the effectiveness of proprioceptive training in conjunction with 3-D visualization techniques. The primary findings were (a) a significant difference (p = .05) in the level of joint position sense in injured vs. healthy subjects; (b) significantly less accurate reproduction of larger shoulder abduction vs. the smaller movement in the active reproduction task; (c) significantly greater ability to accurately reproduce angles actively vs. visually; and (d) that proprioception training using 3-D visualization techniques significantly increased active and visual reproductions of passively placed angles.
Keijo Häkkinen, Markku Alen, Mauri Kallinen, Mikel Izquierdo, Kirsi Jokelainen, Helka Lassila, Esko Mälkiä, William J. Kraemer and Robert U. Newton
Forty-two healthy men and women in two age groups (40 and 70 years) were examined for muscle cross-sectional area (CSA), maximal voluntary bilateral isometric force, force-time characteristics, maximal concentric 1 RM. and power performance of the leg extensors in a sitting position, squat jump, and standing long-jump. The results suggested that the decline in maximal strength with increasing age is related to the decline in muscle CSA; however, particularly in older women, the force/CSA ratio may also be lowered. Explosive force seems to decrease with increasing age even more than maximal strength. suggesting that muscle atrophy with aging is greater in fast-twitch fibers. The voluntary activation of the agonist and antagonist muscles seems to vary depending on the type of muscle action and/or velocity and time duration of the action in both age groups but to a greater extent in older people. There appears to be an age-related increase in antagonist co activation. especially in dynamic explosive movements.