Effects of strength, endurance and combined training on strength development and myosin heavy chain content in man

Introduction

Although previous studies have reported that the effects of strength, endurance and combined training on muscle fiber distributions and fiber cross-sectional area by using ATPase histochemical staining, few studies have compared the effect of endurance training and combined training on muscle myosin heavy chain content in humans by using immunohistochemical staining[1]. Hence, the purpose of this study was to investigate the effect of strength, endurance and combined strength and endurance training on immunohistochemically delineated fiber type transitions, MHC content and fiber cross-sectional areas (CSA) of the lateral aspect of the right vastus lateralis muscle.

Methods

Forty male and female volunteers were randomly assigned separately by gender into one of four groups: resistance training only, endurance training only, concurrent resistance and endurance training, and a control group. Training was performed 3 times a week for the S and E groups and 6 days a week on alternate days for the SE group. Physiological testing was performed prior to and after 6 and 12 weeks of training. The needle biopsy technique was used to take samples of skeletal muscle from the lateral aspect of the right vastus lateralis muscle. Three monoclonal antibodies directed against adult type MHC isoforms were employed analyze fiber type percentage[2] and SDS-PAGE were employed to analyses myosin heavy chain isoform[3]. Separate three-way repeated measures of analysis of variance was performed for dependent variables of fiber type percentage, composition of MHC isoforms content and concentrations of MHC protein isoforms with independent factors of group, sex and time.

Results

Immunohistochemical analyses of muscle biopsies demonstrated a decrease in the percentage of type IID/A mixed fibers after 6 and 12 weeks of training in the S group and after 12 weeks of training in the SE group (P < 0.05). The percentage of type I/IIA mixed fibers increased after 6 and 12 weeks of strength training (P < 0.05). MHC electrophoresis showed that the proportion of MHCIId/x isoform content decreased with all three training regimes after 12 weeks (P < 0.05). An increase in the proportion of MHCIIa content was found in the SE group (P < 0.05). The CSA of type I and type IIA fibers increased after 12 weeks of strength training (p<0.05). In the SE group, the type IIA fibers were the only fibers to display an increase in CSA (P < 0.05).

Discussion / Conclusions

It was concluded that single mode and combined mode
training can elicit differential adaptations in skeletal muscle MHC content and CSA and that combining strength and endurance training may reduce the hypertrophic response associated with strength training only.

References

[1]. Pette, D., et al. Int. Rev. Cytol. 170: 143-223, 1997.
[2]. Schiaffino S. , et al. J. Mus. Res. Cell. Motil., 10: 197-205, 1989.
[3]. Hämäläinen N., et al. FEBS Lett. 399: 220-222, 1996.