| Co-Investigator(Kenkyū-buntansha) |
KANEHISA Hiroaki 鹿屋体育大学, スポーツ生命科学系, 教授 (50161188)
YOSHITAKE Yasuhide 鹿屋体育大学, スポーツ生命科学系, 准教授 (70318822)
MORI Shiro 鹿屋体育大学, スポーツ人文・応用社会科学系, 教授 (80200369)
NAKAMOTO Hiroki 鹿屋体育大学, スポーツ人文・応用社会科学系, 講師 (10423732)
TAKAI Youhei 鹿屋体育大学, スポーツ生命科学系, 助教 (20574205)
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| Research Abstract |
The present study examined if the body mass based exercise in daily life improves strength capability of knee extensor muscles and cognitive functions assessed by by Mini-Mental State Examination (MMSE), in elderly persons.
First, we attempted to clarify how the force-generating capability of quadriceps femoris (QF) is associated to its surface EMG activity during a body mass‐based squat movement. Subjects were 3 men and 48 women age 19-90 yr, including 18 frail elderly persons who used the long-term care insurance system. During body mass‐based squat movement, %EMGmax of QF was nonlinearly related to maximal knee extension torque relative to body mass (KET/BM). Linear piecewise continuous regression analysis showed that there was a breakpoint of 1.9 Nm/kg in the relationship between the two variables. In individuals with KET/BM less than 1.9 Nm/kg, QF %EMGmax rapidly increased as KET/BM decreased. These results indicate that the activity level of QF during a body mass‐based squat movem
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ent is influenced by its force generation capability. For individuals with a KET/BM less than 1.9 Nm/kg, body mass‐based squat movement is considered.
Second, we examined whether the degree to which muscle strength is improved by a body mass-based home exercise program in middle-aged and older women depends on the force generating capabilities of the muscles prior to the intervention. 75 women (53-76 years) voluntarily participated in a circuit training program consisting of 5 exercises (16 repetitions/exercise, 2 or 3 circuits/day) using only body mass as resistance for 3 months. The subjects performed the training program 6 days a week in their own home and once a week in a local gym. After intervention, isometric torques during maximal voluntary knee extension (KET) and plantar flexion (PFT) increased significantly after intervention, and their relative changes were negatively correlated to the absolute values before intervention. Most of the subjects whose KET/BM and PFT/BM values before intervention were greater than 2.8 Nm/kg and 1.7 Nm/kg, respectively, did not show increases in strength after intervention.
These results suggests that body mass-based exercise at home is effective in improving lower limb strength in middle-aged and older women, and the magnitude of the improvement is influenced by the force-generating capability before intervention. Lastly, we examined whether the strength capability of knee extensor muscles is associated with global cognitive function, assessed by Mini-MentalState Examination (MMSE), in non-disabled elderly men. Isometric torques during maximal voluntary knee extension, plantar flexion, and elbow flexion and MMSE scores were determined in 39 non-disabled men aged 61-79 years and used for the cross-sectional analysis examining the associations among the measured variables. Moreover, 27 of the subjects participated in a training program consisted of body mass-based exercises (sitting down onto and standing up from a chair, hip joint extension and flexion, calf raises, side leg raises, and trunk flexion and extension) 6 days a week for 3 months. Isometric torques and MMSE scores were determined after the intervention. Among the data before intervention, only knee extension torque (KET) and KET relative to body mass (KET/BM) significantly correlated to the MMSE scores: r = 0.579 (P < 0.0001) for KET and r = 0.520 (P < 0.001) for KET/BM. After the intervention, KET and KET/BM increased significantly, but MMSE score did not. However, the absolute change in MMSE scores was significantly associated with that in KET (r = 0.381, P < 0.05) and KET/BM (r = 0.422, P < 0.05).These findings indicate that the strength capability of knee extensors is associated with global cognitive function in non-disabled elderly men, and provide a new perspective to a general concept that exercises strengthening knee extensor muscles should be included in resistance training programs for elderly individuals. Less
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