Whey protein improves glycemia during an oral glucose tolerance test compared to vigorous-intensity aerobic exercise in young adult men.

BACKGROUND: Both aerobic exercise and whey protein can improve glucose regulation. The purpose of this study was to investigate how a single bout of vigorous-intensity aerobic exercise and whey protein, independently, as well as when combined, influence glycemia during an oral glucose tolerance test in sedentary, young men. METHODS: Healthy males (n = 11) completed four randomized trials: no exercise/no whey protein (R); exercise (EX; walking at 70% VO2max for 60 min); 50 g of whey protein (W); and exercise combined with 50 g of whey protein (EXW). Each trial included a 75 g oral glucose tolerance test (OGTT) that was completed after an overnight fast. Blood samples were collected over a two-hour period during the OGTT. For EX and EXW, the exercise was performed the evening before the OGTT and the 50 g of whey protein was dissolved in 250 mL of water and was consumed as a preload 30 min prior to the OGTT. For R and EX, participants consumed 250 mL of water prior to the OGTT. Plasma samples were analyzed for glucose, insulin, C-peptide, glucagon, gastric inhibitory peptide (GIP) and glucagon like peptide 1 (GLP-1), and postprandial incremental area under the curve (iAUC) was calculated for each. RESULTS: Glucose iAUC was reduced during W (- 32.9 ± 22.3 mmol/L) compared to R (122.7 ± 29.8 mmol/L; p < 0.01) and EX (154.3 ± 29.2 mmol/L; p < 0.01). Similarly, glucose iAUC was reduced for EXW (17.4 ± 28.9 mmol/L) compared to R and EX (p < 0.01 for both). There were no differences in iAUC for insulin, C-peptide, GIP, GLP-1, and glucagon between the four trials. Insulin, C-peptide, glucagon, GIP, and GLP-1 were elevated during the whey protein preload period for W and EXW compared to EX and R (p < 0.01). There were no differences for insulin, C-peptide, glucagon, GIP, or GLP-1 between trials for the remaining duration of the OGTT. CONCLUSIONS: Glucose responses during an oral glucose tolerance test were improved for W compared to EX. There were no additional improvements in glucose responses when vigorous-intensity aerobic exercise was combined with whey protein (EXW).

Consecutive days of exercise decrease insulin response more than a single exercise session in healthy, inactive men.

PURPOSE: It is reported that a single bout of exercise can lower insulin responses 12-24 h post-exercise; however, the insulin responses to alternate or consecutive bouts of exercise is unknown. Thus, the purpose of this study was to examine the effect of exercise pattern on post-exercise insulin and glucose responses following a glucose challenge. METHODS: Ten male participants (n = 10, mean ± SD, Age 29.5 ± 7.7 years; BMI 25.7 ± 3.0 kg/m2) completed three exercise trials of walking for 60 min at ~ 70% of VO2max. The trials consisted of: three consecutive exercise days (3CON), three alternate exercise days (3ALT), a single bout of exercise (SB), and a no exercise control (R). Twelve to fourteen hours after the last bout of exercise or R, participants completed a 75 g oral glucose tolerance test (OGTT) and blood was collected at 30 min intervals for the measurement of glucose, insulin, and C-peptide. RESULT: Calculated incremental area under the curve (iAUC) for glucose and C-peptide was not different between the four trials. Insulin iAUC decreased 34.9% for 3CON compared to R (p < 0.01). CONCLUSION: Three consecutive days of walking at ~ 70% VO2max improved insulin response following an OGTT compared to no exercise. It is possible, that for healthy males, the effect of a single bout of exercise or exercise bouts separated by more than 24 h may not be enough stimulus to lower insulin responses to a glucose challenge.

Pilot study: an acute bout of high intensity interval exercise increases 12.5 h GH secretion.

The purpose of this study was to test the hypothesis that high-intensity interval exercise (HIE) significantly increases growth hormone (GH) secretion to a greater extent than moderate-intensity continuous exercise (MOD) in young women. Five young, sedentary women (mean ± SD; age: 22.6±1.3 years; BMI: 27.4±3.1 kg/m2 ) were tested during the early follicular phase of their menstrual cycle on three occasions. For each visit, participants reported to the laboratory at 1700 h, exercised from 1730-1800 h, and remained in the laboratory until 0700 h the following morning. The exercise component consisted of either 30-min of moderate-intensity continuous cycling at 50% of measured peak power (MOD), four 30-s "all-out" sprints with 4.5 min of active recovery (HIE), or a time-matched sedentary control using a randomized, cross-over design. The overnight GH secretory profile of each trial was determined from 10-min sampling of venous blood from 1730-0600 h, using deconvolution analysis. Deconvolution GH parameters were log transformed prior to statistical analyses. Calculated GH AUC (0-120 min) was significantly greater in HIE than CON (P = 0.04), but HIE was not different from MOD. Total GH secretory rate (ng/mL/12.5 h) was significantly greater in the HIE than the CON (P = 0.05), but MOD was not different from CON or HIE. Nocturnal GH secretion (ng/mL/7.5 h) was not different between the three trials. For these women, in this pilot study, a single bout of HIE was sufficient to increase 12.5 h pulsatile GH secretion. It remains to be determined if regular HIE may contribute to increased daily GH secretion.

Cardiorespiratory responses during aquatic treadmill exercise and land treadmill exercise in older adults with type 2 diabetes.

BACKGROUND: The purpose of this study was to compare the effect of aquatic treadmill exercise (ATM) to land treadmill exercise (LTM) in adults with and without type 2 diabetes (T2D). METHODS: Five participants with T2D (4 females, 1 male; age=51±3 years; height=170±3 cm; weight=96±11 kg; body fat=32±1%) and five participants without T2D (4 females, 1 male; age=51±3 years; height=170±3 cm; weight=71±15 kg; body fat=27±2%) completed the study. Participants completed three, 5-minute stages of exercise at 3.2 km/h, 4.8 km/h and 6.4 km/h with 0% grade on land and aquatic treadmills. Heart rate (HR), systolic and diastolic blood pressure (SBP and DBP), absolute and relative oxygen consumption (VO2), and energy expenditure were measured at rest and during steady-state exercise at each intensity. A 2x2x4 Mixed Factorial ANOVA and Bonferroni post-hoc test with a significance level of 0.05 was used. RESULTS: All variables increased as speed increased (P<0.05) independent of group or mode. The HR value was higher on the LTM versus the ATM independent of group and treadmill stage (P=0.002) and SBP was higher in the T2D group versus no T2D independent of treadmill mode and stage (P=0.01). Relative VO2 was higher in the group without T2D compared to the T2D group at 6.4 km/h independent of treadmill mode (P=0.032). CONCLUSIONS: Although there is some evidence for the varying effects of aquatic and land exercise when comparing those with and without T2D, cardiorespiratory and metabolic variables are similar in both groups during locomotion on land and in an aquatic environment.

The change in metabolic heat production is a primary mediator of heat acclimation in adults.

PURPOSE: This study examined whether heat acclimation (HA) results in either predominate improvements in heat dissipation or reduced endogenous heat production via individual components of the human heat balance equation. METHODS: Twelve healthy inactive subjects (5 females, mean ± SD): age 28 ± 6y, 77.9 ± 2kg), completed a 10-day HA (42°C, 28% RH) hyperthermia clamp (90min/day exercise, ∆1.5°C in rectal temperature (Tre)) and control workload matched (CON: 23°C, 42% RH) protocols in a counterbalanced design separated by at least 2 mo. Pre-and post-HA were matched for external work rate (EXWR; day 1 and day 10 first 30min at 118 ± 29W, last 60min at 11 ± 5W); and metabolic heat production (Hprod; day 1 and day 9, first 30min at 296 ± 26Wm-2, last 60min 187 ± 33Wm-2). RESULTS: When Pre- and post- HA was matched for Hprod, there was no difference during the first 30 or last 60min of exercise for metabolic energy expenditure (MEE 363 ± 70/ 195 ± 32Wm-2), Hprod (296 ± 67/ 187 ± 33Wm-2) or Tre (∆2.1 ± 0.5°C). When pre- and post-HA was EXWR equivalent, HA significantly attenuated MEE during the first 30 and last 60min (303 ± 49/ 174 ± 35Wm-2), Hprod (241 ± 44/ 168 ± 33, W·m-2), and ∆Tre (∆1.3 ± 0.4°C) (each P < 0.0001). When ∆Tre, ∆Tsk, ∆Tb were each normalized per 100W Hprod, no differences were found for any pre-to post-HA comparison. Heat loss required (Ereq) to maintain steady state internal temperature (Ereq = 220 ± 32Wm-2), maximal capacity of the climate for evaporative heat loss (Emax = 266 ± 56Wm-2), evaporative heat loss from skin (Esk = 207 ± 38Wm-2) or skin wettedness (Ereq/Emax = 0.88 ± 0.23Wm-2) were not different among each condition during the last 60min. CONCLUSION: The mechanisms that underlie heat acclimation are not wholly attributed to heat dissipation enhancements per se, but are significantly influenced by metabolic heat production alterations under uncompensable heat stress environments.

Vitamin D status, body composition, and fitness measures in college-aged students.

Low vitamin D, commonly assessed as serum 25-hydroxyvitamin D (25OHD), is associated with the development of many age-related chronic diseases. A positive relationship exists between elevated 25OHD and muscle synthesis, strength, power, and decreased body fat in elderly individuals. However, these findings have not been consistently reported in younger healthy populations. The purpose of this study was to investigate the relationship between 25OHD and measures of body size, composition, metabolism, and physical fitness in a young physically active population. Thirty-nine subjects (20 men, 19 women; aged 23 ± 0.7 years) reported 6 times for testing. Blood was collected to determine 25OHD. Primary outcomes included the following: body mass index (BMI) and percent body fat (dual x-ray absorptiometry); resting metabolic rate; maximal oxygen uptake (V[Combining Dot Above]O2max); power output (Wingate); and muscular strength (8 repetition maximum for bench press, upright row, and leg extension and flexion exercises). Our analysis included all participants, and subgroup analyses for individuals with suboptimal 25OHD concentration below 35 ng·mL ("low"; n = 20, 25.97 ± 1.97 ng·mL) or equal to and above 35 ng·mL ("high"; n = 19, 44.15 ± 2.17 ng·mL). Twenty subjects in this study had serum levels of 25OHD below 35 ng·mL. There was a significant positive relationship between V[Combining Dot Above]O2max and serum 25OHD and a negative relationship between BMI and serum 25OHD. These data suggest that vitamin D deficiency is prevalent even in a young physically active population in the southern United States and that there was a positive relationship between a measure of cardiovascular fitness and serum 25OHD, and a negative relationship between serum 25OHD and BMI.