Influence of endurance training on central sympathetic outflow to skeletal muscle in response to a mixed meal.
Level 4 - case-series / case-control
Cross-sectional comparative physiological study
PubMed 20110544 · doi:10.1152/japplphysiol.01174.2009
What was done
Plasma insulin, glucose, muscle sympathetic nerve activity (MSNA), heart rate, and arterial blood pressure were measured in 11 high-fit males (peak VO2 65.9 +/- 1.4 ml/kg/min) and 9 average-fit males (peak VO2 43.6 +/- 1.3 ml/kg/min) before and for 120 minutes after ingestion of a mixed meal drink.
What was found
Insulin area under the curve (0-120 min) was lower in high-fit than average-fit participants (2,314 +/- 171 vs. 4,028 +/- 460 microIU x ml(-1) x 120(-1), P < 0.05), with similar plasma glucose responses. High-fit subjects demonstrated a larger increase in MSNA at 120 minutes post-meal compared with average-fit subjects (Delta 21 +/- 1 vs. 8 +/- 3 bursts/100 heart beats, P < 0.05) and a greater change in MSNA relative to plasma insulin. Arterial blood pressure responses were similar between groups.
Why it matters
These findings suggest that endurance fitness may enhance central nervous system sensitivity to insulin, increasing postprandial sympathetic outflow to skeletal muscle despite lower circulating insulin levels.
Limits
The study is limited by a small sample size (n = 20) and inclusion of only male participants. The cross-sectional design compares fitness levels rather than an exercise intervention, precluding direct causal conclusions.
Cited by
- supports Eating food activates sympathetic nervous system activity.