Enhanced physiological tremor deteriorates plantar flexor torque steadiness after bed rest

• Published in: Journal of electromyography and kinesiology 2011-04, Vol.21 (2), p.384-393
• Main Authors: Mulder, Edwin R, Horstman, Astrid M, Gerrits, Karin, Massa, Mark, Kleine, Bert U, de Haan, Arnold, Belavý, Daniel L, Felsenberg, Dieter, Zwarts, Machiel, Stegeman, Dick F
• Format: Article
• Language: English
• Subjects: Adult; BBR2; Bed rest; Bed Rest - adverse effects; H-reflex; Humans; Male; Middle Aged; Muscle Contraction; Muscle Strength; Muscle, Skeletal - physiopathology; Muscular Atrophy - etiology; Muscular Atrophy - physiopathology; Muscular Atrophy - prevention & control; Physical Medicine and Rehabilitation; Reference Values; Resistance Training - methods; Torque; Torque fluctuation; Tremor - etiology; Tremor - physiopathology; Tremor - prevention & control; Triceps surae; Young Adult
• ISSN: 1050-6411; 1873-5711
• DOI: 10.1016/j.jelekin.2010.10.009

Abstract This study evaluated the effectiveness of resistance training to preserve submaximal plantar flexor (PF) torque steadiness following 60 days of bed rest (BR). Twenty-two healthy male subjects underwent either BR only (CTR, n = 8), or BR plus resistance training (RT, n = 14). The magnitude of torque fluctuations during steady submaximal isometric PF contractions (20%, 40%, 60% and 80% of maximum) were assessed before and after BR. Across contraction intensities, torque fluctuations (coefficient of variation, CV) increased more ( P < 0.05) after BR for CTR (from 0.31 ± 0.10 to 0.92 ± 0.63; P < 0.001), than for RT (from 0.30 ± 0.09 to 0.54 ± 0.27; P < 0.01). A shift in the spectral content of torque fluctuations towards increased rhythmic activity between 6.5 and 20 Hz was observed in CTR only ( P < 0.05). H-reflex amplitude ( Hmax / Mmax ratio) declined across groups from 0.57 ± 0.18 before BR to 0.44 ± 0.14 following BR ( P < 0.01) without correlation to CV. The present study showed that increased torque fluctuation after BR resulted from enhanced physiological tremor. Resistance training prevented the spectral shift in isometric PF torque fluctuation and offset ∼50% of the decline in performance associated with long-term BR.