The Effect of Intense Interval Cycle-training on Unloading-Induced Dysfunction and Atrophy in the Human Calf Muscle

Abstract

We investigated whether intense interval training on a cycle ergometer would prevent loss of muscle strength and atrophy in the human calf during unilateral lower limb suspension (ULLS). The present study involved 11 healthy men. We defined unloading leg and contralateral leg as ULLSleg and CONT-leg, respectively. The subjects were divided into 2 groups: one with single-leg cycling training (Tr-UL, nϭ6); the other as a control (UL, nϭ5). The Tr-UL group performed an intense 25-min interval cycling training up to 80% of peak oxygen uptake on alternate days during 20-d ULLS. It was found that: 1) in maximal voluntary contraction (MVC) and the cross-sectional area of the planter flexor, there was a significant time-(pre-ULLS and post-ULLS) by-leg (ULLSleg and CONT-leg) interaction; 2) in voluntary activation during MVC evaluated by the twitch interpolation technique, no significant time-by-leg interaction was detected but the trend of change from before to after ULLS tended to be different between ULLS-leg and CONT-leg; and 3) regarding ULLS-leg, the change in any parameters was not significantly different between the Tr-UL and UL groups. These results suggest that unloading induces dysfunction and atrophy in the human calf and that high-intensity interval training on a cycle ergometer cannot significantly prevent unloading-induced deconditioning in the human calf.

Allopurinol partially prevents disuse muscle atrophy in mice and humans

“…The decline in the muscle size of our patients parallels data from a number of studies that report decreases from 7 to 15% after 20 days of bed rest or unilateral lower limb unloading. Table 1 shows that our intervention (300 mg of allopurinol daily), seems to be as effective as exercise for atrophy prevention 25 – 27 , 41 , 42 . In this regard, we would like to highlight that the atrophic response seems to be higher in the soleus muscle than in the medial and lateral gastrocnemius muscles, in both the animal and human models 26 .…”

Unilateral lower limb suspension: integrative physiological knowledge from the past 20 years (1991–2011)

“…The decline in muscle size is plotted against the duration (up to 42 days) of unloading in the knee extensors and plantar flexors in Fig. 1c, d. Collectively, the observed rates of decline in muscle size for each day of ULLS in knee extensor and plantar flexor size (anatomical CSA or volume) is *0.40 and *0.36%, respectively (Adams et al 1994;Akima et al 2009;Clark et al 2006a;Cook et al 2010;de Boer et al 2007a;Dudley et al 1992a;Hather et al 1992;Hotta et al 2010;Sato et al 2010;Schulze et al 2002;Seynnes et al 2008b;Tesch et al 1994Tesch et al , 2004. These data appear to be similar, but slightly less, than the rate of decline observed in the knee extensors (*0.41% per day) and plantar flexors (*0.42% per day) over the same duration of bed rest (Narici and de Boer 2011).…”

“…1a, b. When evaluated as relatively linear declines, rates of maximal isometric muscle strength loss in the knee extensors and plantar flexors are *0.72 and *0.63%, respectively, for each day of ULLS (Bleeker et al 2005a;Clark et al 2006aClark et al , 2010de Boer et al 2007a;Hotta et al 2010;Schulze et al 2002;Seynnes et al 2008bSeynnes et al , 2010Tesch et al 2004). In the knee extensors, the rate of isometric force loss with ULLS compares very well to what can be interpreted over an equivalent duration of bed rest (*0.73% per day); however, too few studies have examined isometric muscle strength in the plantar flexors following bed rest for general comparisons to be attempted (Narici and de Boer 2011).…”

“…In this regard, central activation capacity and the central activation ratio have been used to make quantitative comparisons following unloading. Using strict statistical analysis, the majority of the studies show that neither central activation capacity nor central activation ratio are significantly decreased following 20-28 days of ULLS (Clark et al 2006b;de Boer et al 2007a;Hotta et al 2010;Seynnes et al 2010). However, although voluntary activation capacity did not decline significantly after 28 days of ULLS when analyzed using ANOVA, this property did account for *50% of the between-person variability in the loss of plantar flexor strength when analyzed using multiple regression (Clark et al 2006b).…”

Muscle-Specific Substrate Use During Cycle Exercise at 1 G: Implications for Astronaut Muscle Health

“…Respiratory measurements were made during the last 5 min of each session (described below). Perceived exertion (Borg scale, [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] was also monitored throughout each 20-min cycling session.…”