Maintenance of myoglobin concentration in human skeletal muscle after heavy resistance training.
The aim of this study was to determine the effects of 8 weeks of resistance training (RT) on the myoglobin concentration ([Mb]) in human skeletal muscle, and to compare the change in the [Mb] in two different RT protocols. The two types of protocol used were interval RT (IRT) of moderate to low intensity with a high number of repetitions and a short recovery time, and repetition RT (RRT) of high intensity with a low number of repetitions and a long recovery time. A group of 11 healthy male adults voluntarily participated in this study and were divided into IRT (n = 6) and RRT (n = 5) groups. Both training protocols were carried out twice a week for 8 weeks. At the completion of the training period, the one-repetition maximal force values and isometric force were increased significantly in all the subjects, by about 38.8% and 26.0%, respectively (P < 0.01). The muscle fibre composition was unchanged by the 8 weeks of training. The muscle fibre cross-sectional areas were increased significantly by both types of training in all fibre types (I, IIa and IIb, mean + 16.1 %, P < 0.05). The [Mb] showed no significant changes at the completion of the training [IRT from 4.63 (SD 0.63) to 4.48 (SD 0.72), RRT from 4.47 (SD 0.75) to 4.24 (SD 0.80) mg x g(-1) wet tissue] despite a significant decrease in citrate synthase activity [IRT from 5.27 (SD 1.45) to 4.49 (SD 1.48), RRT from 5.33 (SD 2.09) to 4.85 (SD 1.87) micromol x min(-1) x g(-1) wet tissue; P < 0.05] observed after both protocols. These results suggested that myoglobin and mitochondria enzymes were regulated by different mechanisms in response to either type of RT. Moreover, the maintained [Mb] in hypertrophied muscle should preserve oxygen transport from capillaries to mitochondria even when diffusion distance is increased.
Masuda
K
K
Doctoral Programme in Health and Sport Sciences, University of Tsukuba, Tsukuba City, Ibaraki, Japan.
Choi
J Y
JY
Shimojo
H
H
Katsuta
S
S
D000328:Adult; D006801:Humans; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000648:ultrastructure; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000378:metabolism*; D009211:Myoglobin / Q000378:metabolism*; D009994:Osmolar Concentration; D013848:Thigh; D014891:Weight Lifting / Q000502:physiology*
D009211:Myoglobin