Naoto Kimura

CREATINE SUPPLEMENTATION ENHANCES ANAEROBIC ATP SYNTHESIS DURING A SINGLE 10 SEC MAXIMAL HANDGRIP EXERCISE

Forearm muscles of twelve healthy male subjects (age = 22.3 ± 1.1 years (mean ± S.E.)) were examined during a 10 sec maximal dynamic handgrip exercise (Ex10) using 31-phosphorus magnetic resonance spectroscopy before and after ingestion with 30 g creatine (Cr) monohydrate or placebo per day for 14 days. Cr supplementation produced a 11.5 ± 4.6% increase in the resting muscle phosphocreatine (PCr) concentration and a 65.0 ± 4.2% increase in the PCr degradation during Ex10. ATP synthesis rate through PCr hydrolysis and total anaerobic ATP synthesis rate during Ex10 increased from 0.64 ± 0.08 (pre-value) to 0.86 ± 0.14 mmol/kg ww/sec (post-value, p < 0.05) and from 0.97 ± 0.16 (pre-value) to 1.33 ± 0.27 mmol/kg ww/sec (post-value, p < 0.05), respectively. An increase in total anaerobic ATP synthesis during Ex10 after Cr supplementation positively correlated with the increase in ATP synthesis through PCr hydrolysis. Cr supplementation produced a 15.1 ± 3.8% increase in the mean power output during Ex10. There was no significant difference in the mean power output per unit of total anaerobic ATP synthesis during Ex10 between before and after Cr supplementation. ATP synthesis rate through PCr hydrolysis positively correlated with mean power output during Ex10 in all twelve subjects after treatment (r = 0.58, p < 0.05). The results suggest that Cr supplementation enhanced PCr degradation during Ex10. It is strongly indicated that an improvement in performance during Ex10 was associated with the increased PCr availability for the synthesis of ATP.

Seasonal variation of trace element loss to sweat during exercise in males

ObjectiveTo clarify the seasonal differences of the trace element excretion in sweat, the trace element concentration in sweat and their loss during exercise were compared between summer and winter.MethodsSweat samples were collected from ten healthy adult males. Bicycle ergometer exercise was conducted by each subject at a heart rate of 140 beats/min for 1 hour, in summer and in winter. Sweat was collected by the arm bag method.ResultsConcentrations of major (Na, K, Ca, and Mg) and trace elements (Zn, Cu, Fe, Ni, Mn, and Cr) in sweat tended to be lower in summer than in winter, and significantly lower concentrations of Mg (p<0.01), Na, Cu, and Mn (p<0.05) were found in summer. The sweat volume in summer (0.90 L) was 1.7-fold larger than that in winter (0.52 L) (p<0.01). The amount of loss of each element to sweat calculated from the concentrations in sweat and sweat volume showed no significant difference between summer and winter.ConclusionsIt is suggested that there was no significant difference in the amount of loss of trace elements in sweat due to exercise between summer and winter.