Ryuta Kinugasa

Short-term creatine supplementation does not improve muscle activation or sprint performance in humans

The purpose of this study was to examine the influence of short-term creatine (Cr) supplementation on exercise-induced transverse relaxation time (T2) and sprint performance during maximum intermittent cycling exercise using the muscle functional magnetic resonance imaging (mfMRI) technique. Twelve men were divided into a Cr supplementation group [the Cr group, taking 4 × (5xa0g Cr monohydrate + 2.5xa0g maltodextrin)/day], or a placebo supplementation group (the P group, taking 4×7.5xa0g maltodextrin/day). The allocation to the groups was based on cycling tests and the subject’s physical characteristics, and thus was not randomized. A double-blind research design was employed for a 5-day supplementation period. mfMR images of the right thigh were collected at rest and immediately after two, five, and ten 6-s sprint bouts of maximum intermittent cycling exercise with a 30-s recovery interval between sets. Before and after supplementation, blood was taken to calculate lactate accumulation, and the muscle volume of the thigh was determined by MRI. Following supplementation, there was significant body mass gain in the Cr group (P<0.05), whereas the P group did not change. The exercise-induced T2, blood lactate levels and sprint performance were not affected by Cr supplementation in any sprint bouts. These results suggest that short-term Cr supplementation does not influence short duration repetitive sprint performance and muscle activation and/or metabolic state during sprint cycling evaluated by mfMRI of the skeletal muscle in humans.

Determinants for stair climbing by elderly from muscle morphology.

The relationship between muscle cross-sectional area (CSA) of the hip joint and lower extremities and speed of stair ascent/descent was investigated in a sample of 127 elderly women (ages: 60–70 years old). The participants performed ascent and descent of stairs with 12 steps for which the speeds for ascent and descent separately from video film were calculated. The ascent speed significantly correlated with CSAs of knee extensor (r = .21, p<.05) and psoas major muscle (r = .25, p<.01), which were assessed by magnetic resonance imaging. The descent speed also correlated with CSAs of the same muscle groups (with knee extensor: r = .20, p<.05, with m. psoas major: r = .18, p<.05). The rest of the muscle groups were not related to the ascent/descent speeds of the step. These results suggested that the muscle mass of the knee extensor muscle group and also the psoas major muscle could be a factor in potential capacity in stair ascent/descent by humans.