Impact of protein and carbohydrate supplementation on plasma volume expansion and thermoregulatory adaptation by aerobic training in older men

Kazunobu Okazaki, Takashi Ichinose, Hiroyuki Mitono, Mian Chen, Shizue Masuki, Hiroshi Endoh, Hideki Hayase, Tatsuya Doi, Hiroshi Nose

Research output: Contribution to journalArticle

35 Citations (Scopus)


We examined whether protein-carbohydrate (CHO) supplementation immediately after exercise each day during aerobic training facilitated plasma volume (PV) expansion and thermoregulatory and cardiovascular adaptations in older men. Fourteen moderately active older men [68 ± 5 (SD) yr] were divided into two groups so as to have no significant differences in anthropometric measures, PV, and peak oxygen consumption rate (V̇O2peak). Each group was provided with a mixture of protein and CHO (3.2 kcal, 0.18 g protein/kg body wt, Pro-CHO, n = 7) or a non-protein and low-calorie placebo (0.5 kcal, 0 g protein/kg body wt, CNT, n = 7) immediately after cycling exercise (60-75% V̇O2peak, 60 min/day, 3 days/wk) each day for 8 wk at ∼19°C ambient temperature (Ta) and ∼43% relative humidity (RH). Before and after training, we measured PV, cardiac stroke volume (SV), and esophageal temperature (Tes) during 20-min exercise at 60% of pretraining V̇O2peak at 30°C Ta and 50% RH. Moreover, we determined the sensitivity of the chest sweat rate (ΔSR/ΔTes) and forearm vascular conductance (ΔFVC/ ΔTes) in response to increased Tes during exercise. After training, PV increased by ∼6% in Pro-CHO (P < 0.001), with an ∼10% increase in SV during exercise (P < 0.001), but not in CNT (P > 0.07). ΔFVC/ΔTes increased by 80% and ΔSR/ΔTes by 18% in Pro-CHO (both P < 0.01) but not in CNT (P > 0.07). Moreover, we found a significant interactive effect of group X training on PV, SV, and ΔFVC/ΔTes (all P < 0.02) but with no significant effect of group (P > 0.4), suggesting that the supplement enhanced these responses to aerobic training. Thus postexercise protein-CHO supplementation during training caused PV expansion and facilitated thermoregulatory and cardiovascular adaptations, possibly providing a new training regimen for older men.

Original languageEnglish
Pages (from-to)725-733
Number of pages9
JournalJournal of Applied Physiology
Issue number3
Publication statusPublished - 2009 Sep 1



  • Aging
  • Exercise
  • Hypervolemia
  • Stroke volume

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

Cite this