Yoshinao Nakagawa

Effect of disuse on the ultrastructure of the achilles tendon in rats

SummaryWe examined the influence exerted, through disuse of the hindlimb, on the collagen fibres of the achilles tendon in rats. With disuse the body mass decreased by 28%, and the mass of soleus muscle decreased by 20%. A decrease in the surface area and diameter was observed in the experimental group when compared to the control group. A histogram of the collagen fibres showed a decrease of the thick fibres in the experimental group. The maximum surface area of collagen fibres in the experimental group was seen to be only 43% of that of the control group. These results showed a decrease in the thickness of the collagen fibres of the achilles tendon through disuse. This seemed to suggest that resistance to tension is decreased by disuse.

Intramyocellular lipids of muscle type in athletes of different sport disciplines

The present study used magnetic resonance spectroscopy (1H-MRS) to examine quantitative differences in intramyocellular lipid (IMCL) contents in various muscle types at rest for individual athletes from different sport disciplines. Five groups consisting of sprinters, alpine skiers, cross-country skiers, endurance runners and untrained healthy male subjects volunteered for this study. Data were acquired using 1H-MRS from the tibialis anterior (TA), medial gastrocnemius (MG) and soleus (SOL) muscles. No significant difference was found in the cross-sectional area (CSA) of the TA, MG and SOL muscles, whereas the CSA of subcutaneous fat was significantly lower (p<0.01) for each athlete group compared with untrained subjects. In both TA and MG, IMCL concentrations in endurance runners were significantly higher than those of alpine skiers (p<0.01), sprinters (p<0.01) and untrained subjects (p<0.05). The IMCL concentrations in TA and MG of cross-country skiers were significantly higher than those of alpine skiers (p<0.05) and sprinters (TA, p<0.01; MG, p<0.05). There was no significant difference in the IMCL concentrations of TA and MG between alpine skiers or sprinters and untrained subjects. The IMCL concentration in SOL was significantly greater in endurance runners and showed no difference in cross-country skiers compared with that in alpine skiers and sprinters. There was no significant difference in the IMCL concentration of SOL between athletes and untrained subjects. These results suggest that differences in IMCL contents stored in various muscle types for athletes at rest are associated with the muscle cellular adaptation for differences in the type of exercise training and/or muscle fiber composition.

Effect of Pole-Assisted Walking on Intramuscular Lipids in Elderly Nursing Home Residents

The present study investigated the effects of a 10 week walking program using hiking poles on intra-and extramyocellular lipid (IMCL and EMCL) content in elderly as assessed by 1H-MR spectroscopy. Six nursing home residents aged between 65 and 84 years (n=6) participated in the study. The subjects were asked to walk for at least 30 minutes a day, three days per week. Intramuscular and blood lipid concentrations were obtained at baseline and at after the 10 week study. 1H-MR spectra were acquired from the tibialis anterior (TA), soleus (SOL) and medial gastrocnemius (MG) muscles. Significant difference was not observed in IMCL concentrations on between before and after pole-assisted walking (PW) program (NS). A significant reduction was recognized in EMCL concentrations and EMCL/IMCL ratio on TA (p<0.05) and MG (p<0.01) between the values before PW and those after. Mean HDLC (p<0.01) and TC (p<0.05) concentrations increased after completion of the PW program. A decrease in VLDL-C (p<0.05) and HDL-C/LDL-C ratio (p<0.01) was also observed at this point. These results show that the PW program induces a decrease in intramuscular lipids and improves lipoprotein profiles in the elderly nursing home residents.