Aerobic training-induced plasma volume (PV) expansion improves thermoregulation, and carbohydrate (CHO) + whey protein supplementation enhanced the effects in older people; however, these were suggested by studies on gym-based cycling training but not on home-based interval walking training (IWT). Moreover, long-term walking training effects on PV remain unknown.
Seventeen male and 10 female subjects (~69 yr), having performed IWT for ≥24 months before the study, were used. After pre-intervention measurement (PRE) of PV, plasma albumin content (Albcont), fasting glucose concentration ([Glc]f), and HbA1c, the subjects were randomly divided into two groups: CHO and Pro-CHO, either consuming CHO (22.5 g) alone or CHO (15 g) + whey protein (10 g), respectively, during additional 5-month IWT from May to November, 2009. After the additional IWT, we measured the same variables again (postintervention measurement).
The baseline PV and Albcont were significantly correlated with the number of IWT days for the 12 months preceding PRE (r = 0.716, P < 0.001 and r = 0.671, P < 0.001, respectively). In postintervention, PV and Albcont marginally decreased in CHO from the baselines (P = 0.081 and P = 0.130, respectively) with increased HbA1c (P < 0.001) after correction for the baseline [Glc]f by ANCOVA, but these values remained unchanged in Pro-CHO (both, P > 0.74), with significant differences in the changes between groups (P = 0.020, P = 0.041, and P = 0.018 respectively).
PV was proportional to the number of IWT days for 12 months and a CHO + whey protein supplementation during the 5-month IWT prevented PV reduction for the period of no supplementation, which might be partially linked with blood glucose control mechanisms.
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1Department of Sports Medical Sciences, Shinshu University Graduate School of Medicine and Institute for Biomedical Sciences, JAPAN; and 2Saga Nutraceutical Research Institute, Otsuka Pharmaceutical CO., Ltd., Higashisefuri, Kanzaki, JAPAN
Address for correspondence: Hiroshi Nose, M.D., Ph.D., Department of Sports Medical Sciences, Shinshu University Graduate School of Medicine and Institute for Biomedical Sciences, 3-1-1 Asahi Matsumoto 390-8621, Japan; E-mail: email@example.com.
Submitted for publication April 2017.
Accepted for publication August 2017.
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