Table 3.

Effects of time of day on metabolic and neuroendocrine effects of exercise

Early Morning (n = 5) Afternoon (n = 8) Night (n = 9) Afternoon vs. Early Morning Night vs. Early Morning Afternoon vs. Night
Difference in area under the curve or amount secreted
 Plasma glucose, mg ⋅ min ⋅ dl−1 −2,665 ± 840 −2,945 ± 713−4,952 ± 584 NS P < 0.05 P < 0.05
 Insulin secretion, nmol−16.7 ± 4.1 −16.0 ± 4.6−19.0 ± 3.9 NS NS NS
 Plasma cortisol, μg ⋅ min ⋅ dl−1 −64 ± 194 +950 ± 318 +146 ± 237 P < 0.05 NS P < 0.05
 GH secretion, μg 158 ± 54 191 ± 46183 ± 81 NS NS NS
 Plasma TSH, % of basal ⋅ min +6,229 ± 958+6,376 ± 1,833 +13,532 ± 1,936 NS P < 0.05 P < 0.01
Maximum difference in concentration or secretory rate
 Plasma glucose, mg/dl −31.2 ± 4.7 −27.2 ± 4.9−41.0 ± 3.9 NS NS P < 0.05
 Insulin secretion, pmol/min −164 ± 23−195 ± 35 −191 ± 25 NS NS NS
 Plasma cortisol, μg/dl +3.7 ± 1.6+9.9 ± 2.2 +5.3 ± 2.1 NS NS NS
 GH secretory rate, μg/min 3.4 ± 1.03.6 ± 0.6 4.5 ± 1.9 NS NS NS
 Plasma TSH, % of basal +49 ± 11 +55 ± 12+92 ± 10 NS P < 0.05 P < 0.05
Duration of response to exercise, min
 Plasma glucose 228 ± 29 298 ± 18316 ± 12 P < 0.05 P < 0.01 NS
 Insulin secretion276 ± 28 300 ± 21 318 ± 15 NSNS NS
 Plasma cortisol 80 ± 30223 ± 47 113 ± 35 P < 0.05NS P < 0.05
 GH secretory rate112 ± 21 113 ± 21 120 ± 16 NSNS NS
 Plasma TSH 236 ± 32198 ± 30 291 ± 19 NS NS P < 0.05