Robert D. Sawyer

Minimum rest period for strength recovery during a common isokinetic testing protocol.

PURPOSE The intent of this investigation was to determine the minimal time for a between sets rest period during a common isokinetic knee extension strength-testing protocol. Based on a review of the literature, a set was considered a group of four maximal coupled contractions at a specific velocity. METHODS Eleven normal, healthy college-age men underwent unilateral knee extension testing to determine their individual isokinetic peak torque at 60, 120, 180, 240, and 300 degrees.s-1. Velocities were administered in ascending order. Between sets, rest periods of 15, 60, 180, and 300 s were assigned to subjects in a counterbalanced fashion. RESULTS There were no differences in peak torque at the beginning velocity of 60 degrees.s-1 among any of the rest periods. At 120 degrees.s-1, peak torque production during the 15-s rest period trial was similar to 60 s but lower than 180 and 300 s. Peak torques at 180, 240, and 300 degrees.s-1 produced during the 15-s rest period test were significantly lower than measured torques at the same velocities during the 60, 180, and 300-s rest period tests (P < 0.05). There were no differences in peak torque production between the 60, 180, and 300-s rest period tests. CONCLUSION These data demonstrate that during a common isokinetic strength testing protocol a between set rest period of at least 60 s is sufficient for recovery before the next test set.

Single muscle fiber myosin heavy chain distribution in elite female track athletes.

PURPOSE Myosin heavy chain (MHC) characterization of tissue samples from the gastrocnemius muscle of six elite female athletes and 10 untrained females was performed using myosin ATPase histochemistry and gel electrophoresis. Athletes were of national and international caliber, whereas their untrained counterparts were healthy individuals not involved in a regular exercise program. METHODS Muscle biopsies for the athletes were performed 14 wk into their training season and analyzed with sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and myosin ATPase techniques. RESULTS Electrophoretic analysis of single muscle fibers from elite athletes revealed a MHC phenotype composition of 46 +/- 6% type I, 21 +/- 6% type IIa, and 0% type IIx, whereas 34% of the single fibers expressed multiple MHC isoforms. When compared with the elite women, untrained subjects demonstrated higher percentages of type I MHC and lower percentages of IIa MHC muscle fibers, 57 +/- 5 and 16 +/- 3%, respectively (P < 0.05). Similar to the female athletes, 27% of the fibers from untrained women possessed multiple myosin isoforms. Myosin ATPase staining demonstrated a greater percentage of type I fibers in untrained subjects versus the elite women (67 +/- 3 vs 41 +/- 2%, P< 0.05) (mean +/- SE), whereas the athletes had a higher percentage of type IIa fibers compared with the untrained women (49 +/- 5 vs 19 +/- 2%, P< 0.05). There were no differences in the percentage of IIb fibers between elite and untrained women (11 +/- 4 vs 14 +/- 2%, respectively). CONCLUSIONS Whereas a preponderance of hybrid fibers is generally observed in untrained populations, the diverse MHC phenotype seen in these elite female athletes is uncommon. These unique findings are attributed to the chronic and varied nature of training in which these athletes were involved.

Structural protein alterations to resistance and endurance cycling exercise training.

Parcell, AC, Woolstenhulme, MT, and Sawyer, RD. Structural protein alterations to resistance and endurance cycling exercise training. J Strength Cond Res 23(2): 359-365, 2009-The muscle cytoskeleton is necessary for the effective transmission of forces generated by actin-myosin interactions. We have examined the impact of muscle force and exercise volume on the cytoskeleton by measuring desmin and dystrophin content in human skeletal muscle after 12 weeks of progressive resistance or endurance cycle training. Muscle biopsies of the vastus lateralis were obtained before and after training. Desmin and dystrophin content was determined using immunoblotting techniques. After resistance training, desmin content increased 82 ± 18% (p < 0.05), whereas there was no change in desmin content with endurance cycling. Dystrophin content did not change in either group. One-repetition maximum and &OV0312;o2max increased (p < 0.05) in the resistance and endurance groups, respectively. These data demonstrate that a high-tension stimulus impacts the cytoskeleton in contrast to high-volume concentric contractions. The tensile loading and eccentric components of resistance training are implicated in desmin alterations. Indeed, the functional improvements resulting from resistance training may be related in part to the mechanical integration provided by the desmin protein.