Early-phase musculoskeletal adaptations to different levels of eccentric resistance after 8 weeks of lower body training
Eccentric muscle actions are important to the development of muscle mass and strength and may affect bone mineral density (BMD). This study’s purpose was to determine the relative effectiveness of five different eccentric:concentric load ratios to increase musculoskeletal parameters during early adaptations to resistance training.
Forty male subjects performed a supine leg press and calf press training program 3 days week−1 for 8 weeks. Subjects were matched for pre-training leg press 1-repetition maximum strength (1-RM) and randomly assigned to one of five training groups. Concentric training load (% 1-RM) was constant across groups, but within groups, eccentric load was 0, 33, 66, 100, or 138 % of concentric load. Muscle mass (dual energy X-ray absorptiometry; DXA), strength (1-RM), and BMD (DXA) were measured pre- and post-training. Markers of bone metabolism were assessed pre-, mid- and post-training.
The increase in leg press 1-RM in the 138 % group (20 ± 4 %) was significantly greater (P < 0.05) than the 0 % (8 ± 3 %), 33 % (8 ± 5 %) and 66 % (8 ± 4 %) groups, but not the 100 % group (13 ± 6 %; P = 0.15). All groups, except the 0 % group, increased calf press 1-RM (P < 0.05). Leg lean mass and greater trochanter BMD were increased only in the 138 % group (P < 0.05).
Early-phase adaptations to eccentric overload training include increases in muscle mass and site-specific increases in BMD and muscle strength which are not present or are less with traditional and eccentric underload training. Eccentric overload provides a robust musculoskeletal stimulus that may benefit bedridden patients, individuals recovering from injury or illness, and astronauts during spaceflight.
KeywordsMuscle strength Hypertrophy Bone mineral density Bone formation Bone resorption Spaceflight Eccentric overload Eccentric underload
Advanced Resistive Exercise Device
Bone mineral density
Dual energy X-ray absorptiometry
interim Resistive Exercise Device
International Space Station
Johnson Space Center
Leg lean mass
National Aeronautics and Space Administration
Peripheral quantitative computed tomography
Whole body lean mass
We would like to thank the subjects for their participation in this training study; Karen Paulder, Sydney Stein, and Leah Stroud for their assistance with exercise training and data collection; Mary Jane Maddocks of the NASA JSC Bone and Mineral Laboratory for acquisition and analysis of DXA scans; the NASA JSC Nutritional Biochemistry Laboratory for the collection and analysis of blood and urine samples; Dr. Mitzi Laughlin for statistical analysis; Drs. Brian Arenare, Todd Schlegel, and Linda Shackelford for medical monitoring; the NASA JSC Human Test Subject Facility for test subject recruitment; Jackie Reeves and Dr. Meghan Downs for editorial and technical review of the manuscript; and Linda Loerch, Dr. Jennifer Tuxhorn, and Dr. Clarence Sams for their programmatic support of this research. Finally, we will always be grateful for the mentoring, support, and friendship of our NASA JSC Exercise Physiology Laboratory lead, the late Dr. R. Donald Hagan.
Conflict of interest
The authors declare that they have no conflicts of interest.
The experiments described herein were conducted in compliance with the laws of the United States of America.
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