Effect of high-frequency resistance exercise on adaptive responses in skeletal muscle.
OBJECTIVE
Regulation of skeletal muscle mass is highly dependent on contractile loading. The purpose of this study was to examine changes in growth factor and inflammatory pathways following high-frequency resistance training.


METHODS
Using a novel design in which male Sprague-Dawley rats undertook a "stacked" resistance training protocol designed to generate a summation of transient exercise-induced signaling responses (four bouts of three sets x 10 repetitions of squat exercise, separated by 3 h of recovery), we determined the effects of high training frequency on signaling pathways and transcriptional activity regulating muscle mass.


RESULTS
The stacked training regimen resulted in acute suppression of insulin-like growth factor 1 mRNA abundance (P < 0.05) and Akt phosphorylation (P < 0.05), an effect that persisted 48 h after the final training bout. Conversely, stacked training elicited a coordinated increase in the expression of tumor necrosis factor alpha, inhibitor kappa B kinase alpha/beta activity (P < 0.05), and p38 mitogen-activated protein kinase phosphorylation (P < 0.05) at 3 h after each training bout. In addition, the stacked series of resistance exercise bouts induced an increase in p70 S6 kinase phosphorylation 3 h after bouts x3 and x4, independent of the phosphorylation state of Akt.


CONCLUSIONS
Our results indicate that high resistance training frequency extends the transient activation of inflammatory signaling cascades, concomitant with persistent suppression of key mediators of anabolic responses. We provide novel insights into the effects of the timing of exercise-induced overload and recovery on signal transduction pathways and transcriptional activity regulating skeletal muscle mass in vivo.
Coffey
Vernon G
VG
Exercise Metabolism Group, RMIT University, Bundoora, AUSTRALIA. vernon.coffey@rmit.edu.au
Reeder
Donald W
DW
Lancaster
Graeme I
GI
Yeo
Wee Kian
WK
Febbraio
Mark A
MA
Yaspelkis
Ben B
BB
Hawley
John A
JA
D000222:Adaptation, Physiological; D000818:Animals; D016207:Cytokines / Q000378:metabolism; D006003:Glycogen / Q000378:metabolism; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D010085:Oxidative Phosphorylation; D010805:Physical Conditioning, Animal / Q000379:methods; D005082:Physical Exertion / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D013997:Time Factors
D016207:Cytokines; D012333:RNA, Messenger; D006003:Glycogen; D017526:Receptor, IGF Type 1