Robert T. Harris’s research while affiliated with Ohio University and other places

This study compared hypertrophy of the left quadriceps femoris (QF) after sedentary subjects trained 2 days a week for 9 weeks using electrical stimulation or voluntary effort. Each day, 3 to 5 sets of 10 lengthening and shortening actions were performed. Maximal effort was used for voluntary training. Electrical stimulation evoked tetanic force in 50% or more of the QF. Muscle cross-sectional area, determined by MR imaging, showed a group x time x leg interaction (p < 0.05). This reflected a 10% increase for the left QF with electrical stimulation as compared to the 4% increase after voluntary training. The right, untrained QF did not change in size (p > 0.05) after either intervention. Voluntary and electrical stimulation trainees, respectively, showed 25 and 56% increases (p < 0.05) in training torque. The results suggest that voluntary effort limits hypertrophy early in resistance training, as done in this study. (C) 1995 National Strength and Conditioning Association

The purpose of this study was to map the pattern of muscle contractile activity elicited by electromyostimulation (EMS). A secondary interest was to determine whether EMS evoked a different pattern of contractile activity than voluntary (VOL) efforts. These objectives were addressed by examining the pattern and extent of contrast shift in magnetic resonance (MR) images after isometric actions of the left m. quadriceps of seven subjects had been elicited by EMS (1-s train of 500-microseconds sine wave pulses at 50 Hz) or by VOL means. For both conditions, five sets of 10 muscle actions were executed at each of the three force levels equal to 25, 50, and 75% of maximal VOL isometric torque. There were 1-s, 1.5-min, and 30-min rests between muscle actions, sets, and torque levels, respectively. Transaxial proton MR images (TR/TE = 2,000/30, 60) of m. quadriceps femoris were obtained with a 1.5-T imager at rest and after completion of the five sets of isometric actions at each force level. MR image contrast shift, as indicated by T2 values > 1 SD above the mean resting muscle T2, was calculated per pixel. Torque declined approximately 18% (P < 0.05) during each EMS set independent of the preset relative force level but recovered between sets. EMS increased T2 values above rest (29 +/- 0.2 to 36 +/- 0.5, P < 0.05) in regions of muscle dispersed throughout a given cross section. The pattern of muscle stimulation, as reflected by increased T2 values, varied markedly among subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Maintenance of a low energy expenditure during exercise in space is important because of the confined environment of the space craft. Resistance exercise is receiving increased attention as an exercise countermeasure, and we have shown that training with concentric (con) and eccentric (ecc) muscle actions induces greater increases in strength than training with only con actions. This study determined if performance of both actions markedly increased the metabolic cost of resistance exercise. Seventeen middle-age males performed each repetition of a "warm-up" and four sets of the leg press exercise with only con (Group CON, n = 8) or with con and ecc (Group CON/ECC, n = 9) actions. Sets were separated by 3 min of rest and each was performed to failure by selecting a resistance that allowed performance of the prescribed number of repetitions (7 to 10). The net energy cost of exercise was estimated from oxygen consumption data that were obtained at rest before exercise, during exercise, and for 20 min of recovery. The total work performed during the con actions was about 290 J.kg-1 body weight for both groups. The energy cost for this work was about 3 x 10(-3) cal.J-1. The requirement for the CON/ECC group to also lower the load increased (p less than 0.05) the energy cost 14%. These results indicate that con actions are mainly responsible for the metabolic cost of resistance exercise. Because ecc actions enhance the resistance training-induced increases in strength that are evident with only con actions with minimal additional energy cost, we suggest that they be considered in exercise prescriptions for use in space.