Submitted on March 2, 2009
Revised on September 23, 2009
Accepted on September 28, 2009
Influence of vibration resistance training on knee extensor and plantar flexor size, strength, and contractile speed characteristics after 60 days of bed rest
Edwin R. Mulder1*, Astrid M. Horstman2, Dick F. Stegeman3, Arnold de Haan4, Daniel L. Belav
5, Tanja Miokovic5, Gabi Armbrecht5, Dieter Felsenberg6, and Karin H. Gerrits7
1 Donders Institute for Brain, Cognition and Behaviour, Centre for Neuroscience, Radboud University Nijmegen Medical Centre
2 VU University Amsterdam
3 Radboud University Nijmegen, Donders Centre for Neuroscience, Mediacal Centre
4 Research Institute MOVE, VU University Amsterdam
5 Charité Campus Benjamin Franklin, Free University & Humboldt University Berlin
6 Charité campus Benjamin Franklin
7 Research Institute MOVE, VU University
* To whom correspondence should be addressed. E-mail: e.mulder{at}neuro.umcn.nl.
Spaceflight and bed rest (BR) result in loss of muscle mass and strength. This study evaluated the effectiveness of resistance training and vibration-augmented resistance training to preserve thigh (quadriceps femoris) and calf (triceps surae) muscle cross-sectional area (CSA), isometric maximal voluntary contraction (MVC), isometric contractile speed, and neural activation (EMG) during 60 days of BR. Male subjects participating in the 2nd Berlin BedRest Study (BBR2) underwent BR only (CTR, n = 9), BR with resistance training (RE, n = 7) or BR with vibration-augmented resistance training 3 times per week (RVE, n = 7). Thigh CSA and MVC decreased by 13.5% and 21.3% for CTR (both P < 0.001), but were preserved for RE and RVE. Calf CSA declined for all groups, but more (P < 0.001) for CTR (23.8%) than for RE (10.7%) and RVE (11.0%). Loss in calf MVC was greater (P < 0.05) for CTR (24.9%) than for RVE (12.3%), but not different from RE (14.8%). Neural activation at MVC remained unchanged in all groups. For indices related to rate of torque development, countermeasure subjects were pooled into one resistance training group (RT, n = 14). Thigh maximal rate of torque development (MRTD) and contractile impulse remained unaltered for CTR, but MRTD decreased 16% for RT. Calf MRTD remained unaltered for both groups, whereas contractile impulse increased across groups (28.8%) despite suppression in peak EMG (12.1%). In conclusion, vibration exposure did not enhance the efficacy of resistance training to preserve thigh and calf neuromuscular function during BR, though sample size issues may have played a role. The exercise regimen maintained thigh size and MVC strength, but promoted a loss in contractile speed. Whereas contractile speed improved for the calf, the exercise regimen only partially preserved calf size and MVC strength. Modification of the exercise regimen seems warranted.
