Fat energy use and plasma lipid changes associated with exercise intensity and temperature

Summary

The effect of 60 min of exercise at two intensities (50 and 60%$\dot V_{O_2 \max }$) and temperatures (0 and 22° C) on changes (A) in plasma lipids {triglycerides (TG), glycerol (GLY), total cholesterol (TC), and HDL-cholesterol (HDL-C)} was examined. Subjects were 10 men aged 27±7 years ($\dot V_{O_2 \max } = 3.81 \pm 0.451\min$, % fat=12.2%±7.1%).$\dot V_{O_2 }$ and respiratory exchange ratio results indicated that total energy and fat energy use were similar at the two temperatures. Changes in plasma volume (%ΔPV) were different (P<0.05) at the two temperatures (22° C: −2.3% vs 0° C: 1.1%). Combining the data at each temperature revealed that the increases in concentrations were greater (P<0.05) at 22° C (ΔTG=0.22, ΔGLY=0.20, ΔTC=0.14, ΔHDL-C=0.05 mmol 1⁻¹) vs 0° C (ΔTG=0.10, ΔGLY=0.12, ΔTC=0.05, ΔHDL-C=0.02 mmol 1⁻¹). Combining the data for each intensity revealed that the increases in concentration were greater (P<0.05) at 60%$\dot V_{O_2 \max }$ for ΔTG and ΔHDL-C. The 60%$\dot V_{O_2 \max } /22^o C$ C bout produced greater changes (P<0.05) than all other bouts for ΔTC and ΔHDL-C (0.21 and 0.08 mmol 1⁻¹, respectively). Only ΔTG and ΔGLY were greater at 22° C when adjusted for %ΔPV. These metabolic and plasma lipid results indicate that cold exposure does not act synergistically with exercise to further stimulate fat metabolism.