Peer 2 peer: efficacy of a course-based peer education intervention to increase physical activity among college students.

UNLABELLED: There are few physical activity (PA) interventions in higher education, and they have been only minimally effective. OBJECTIVE: To determine if a course-based, peer education intervention was associated with increases in PA and physical fitness. PARTICIPANTS: Participants were 178 students enrolled in a personal health class during the 2007-2008 academic year. METHODS: A quasi-experimental design was used to assess the effect of the intervention. Repeated measures analysis of covariance was employed to test the impact of the intervention on students' PA, body composition, waist-to-hip ratio, cardiovascular fitness, flexibility, and muscular strength. RESULTS: Women in the treatment group classified as "Inactive" at baseline increased PA, whereas "Inactive" control women had reductions in PA. Women in the treatment group who were "Active" at baseline reduced their waist-to-hip ratio and increased flexibility. There were no differences by treatment group among men. CONCLUSIONS: The intervention was effective in improving PA and physical fitness among college women.

Glycemic and insulinemic responses to different preexercise snacks in participants with impaired fasting glucose.

PURPOSE: To compare serum glucose and insulin responses to 3 preexercise snacks before, during, and after exercise in individuals with impaired fasting glucose (IFG) and healthy (H) men. In addition, in an IFG population, the authors sought to determine whether a natural fruit snack (i.e., raisins) yields more desirable glucose and insulin concentrations than an energy bar or a glucose solution. METHODS: The IFG (n = 11, age = 54.5 ± 1.3 yr, fasting blood glucose [BG] = 6.3 ± 0.1 mmol/L) and H groups (n = 9, age = 48.0 ± 3.1 yr, fasting BG = 4.9 ± 0.1 mmol/L) cycled at 50% of VO2peak for 45 min on 4 occasions after consuming water or 50 g of carbohydrate from raisins (R), an energy bar (EB), or a glucose beverage (GLU). Metabolic markers were measured before, during, and after exercise. RESULTS: In all nutritional conditions, glucose concentrations of the IFG group were consistently higher than in the H group. Differences between IFG and H groups in insulin concentrations were sporadic and isolated. In the IFG group, preexercise glucose concentration was lower in the R condition than in GLU. Ten and 20 min into exercise, glucose concentrations in the R and EB conditions were lower than in GLU. Insulin concentrations were lower in the R condition than in EB and GLU immediately before exercise and at Minute 10 but at 20 min R remained lower than only GLU. CONCLUSION: Glucose concentrations were higher in the IFG group regardless of preexercise snack. Compared with the glucose solution, raisins lowered both the postprandial glycemic and insulinemic responses, whereas the energy bar reduced glycemia but not insulinemia.

Raisins are a low to moderate glycemic index food with a correspondingly low insulin index.

The objective of this study was to determine the glycemic index (GI) and insulin index (II) of raisins and evaluate if these values are similar in different populations. The study subjects consisted of 10 healthy sedentary individuals (S; age, 25.7 +/- 1.3 years; body mass index [BMI] = 23.3 +/- 1.7 kg/m(2)), 11 aerobically trained adults (A; age, 23.1 +/- 1.0 years; BMI = 24.1 +/- 0.3 kg/m(2)), and 10 prediabetic adults (P; age, 50.0 +/- 2.6 years; BMI = 32.6 +/- 1.9 kg/m(2)). Subjects consumed 50 g of available carbohydrate from raisins and from a glucose solution (reference food) on 2 separate occasions. Serum glucose and insulin concentrations were measured from capillary fingerstick blood samples at baseline and at 15, 30, 45, 60, 90, and 120 minutes (and 150 and 180 minutes for P group) postprandially. The GI of raisins was low (GI, < or = 55) in the S (49.4 +/- 7.4) and P (49.6 +/- 4.8) groups and was moderate (GI, 55-69) in the A group (62.3 +/- 10.5), but there were no differences among the subject groups (P = .437). The II of raisins was 47.3 +/- 9.4, 51.9 +/- 6.5, and 54.4 +/- 8.9 for the S, A, and P groups, respectively. On average, the A group secreted 2- to 2.5-fold less insulin per gram of carbohydrate compared with the S and P groups (P < .05). Thus, raisins are a low to moderate GI food, with a correspondingly low II. The lower insulin response in the A group compared with the other groups suggests enhanced insulin sensitivity.

Ratings of perceived exertion are not influenced by exercise stage of change in physically active college students.

Comparisons of ratings of perceived exertion based on fitness have been equivocal but have not accounted for recent exercise history. The purpose of this study was to test mean differences in ratings of perceived exertion among individuals of differing exercise histories as measured by exercise stage of change. Participants completed questionnaires to measure exercise stage of change and physical activity [preparation stage (n=32), action stage (n=31), and maintenance stage (n=41)]. Ratings of perceived exertion were measured during a graded maximal exercise test. Individual regression equations were computed to estimate the ratings for 50%, 60%, 70%, and 80% of VO2 max. There were no significant differences in the ratings across the preparation, action, and maintenance stages. Therefore, the hypothesis that recent exercise history would influence ratings of perceived exertion during an aerobic fitness test was rejected.

Maximal lactate steady state declines during the aging process.

Increased participation of aged individuals in athletics warrants basic research focused on delineating age-related changes in performance variables. On the basis of potential age-related declines in aerobic enzyme activities and a shift in the expression of myosin heavy chain (MHC) isoforms, we hypothesized that maximal lactate steady-state (MLSS) exercise intensity would be altered as a function of age. Three age groups [young athletes (YA), 25.9 +/- 1.0 yr, middle-age athletes (MA), 43.2 +/- 1.0 yr, and older athletes (OA), 64.6 +/- 2.7 yr] of male, competitive cyclists and triathletes matched for training intensity and duration were studied. Subjects performed a maximal O2 consumption (V(o2 max)) test followed by a series of 30-min exercise trials to determine MLSS. A muscle biopsy of the vastus lateralis was procured on a separate visit. There were differences (P < 0.05) in V(o2 max) among all age groups (YA = 67.7 +/- 1.2 ml x kg-1x min-1, MA = 56.0 +/- 2.6 ml x kg-1x min-1, OA = 47.0 +/- 2.6 ml x kg-1 x min-1). When expressed as a percentage of V(o2 max), there was also an age-related decrease (P < 0.05) in the relative MLSS exercise intensity (YA = 80.8 +/- 0.9%, MA = 76.1 +/- 1.4%, OA = 69.9 +/- 1.5%). There were no significant age-related changes in citrate synthase activity or MHC isoform profile. The hypothesis is supported as there is an age-related decline in MLSS exercise intensity in athletes matched for training intensity and duration. Although type I MHC isoform, combined with age, is helpful in predicting (r = 0.76, P < 0.05) relative MLSS intensity, it does not explain the age-related decline in MLSS.

Influence of racial origin and skeletal muscle properties on disease prevalence and physical performance.

Skeletal muscle properties are related to disease (e.g. obesity) and physical performance. For example, a predominance of type I muscle fibres is associated with better performance in endurance sports and a lower risk of obesity. Disease and physical performance also differ among certain racial groups. African Americans are more likely than Caucasians to develop obesity, diabetes mellitus and hypertension. Empirical studies indicate that aerobic capacity is lower in African Americans than Caucasians. Because genetics is a partial determinant of skeletal muscle properties, it is reasonable to assume that skeletal muscle properties vary as a function of race. As such, genetically determined and race-specific skeletal muscle properties may partially explain racial disparities in disease and physical performance. However, additional research is needed in this area to enable the development of more definitive conclusions.

Hypohydration adversely affects lactate threshold in endurance athletes.

The purpose of this investigation was to observe the effect of hypohydration (-4% body mass) on lactate threshold (LAT) in 14 collegiate athletes (8 men and 6 women; age, 20.9 +/- 0.5 years; height, 171.1 +/- 2.4 cm; weight, 64.8 +/- 2.3 kg; V(O)2 max, 62.8 +/- 1.9 ml x kg(-1) x min(-1); percentage of fat, 11.4 +/- 1.5%). Subjects performed 2 randomized, discontinuous treadmill bouts at a dry bulb temperature (T(db)) of 22 degrees C to volitional exhaustion in 2 states of hydration, euhydrated and hypohydrated. The hypohydrated condition was achieved in a thermally neutral environment (T(db), 22 degrees C; humidity, 45%), with exercise conducted at a moderate intensity as defined by rating of perceived exertion (RPE, approximately 12) 12-16 hours before testing. On average, subjects decreased 3.9% of their body mass before the hypohydration test. Blood lactate, hematocrit, V(O)2, minute ventilation (VE), R value, heart rate (HR), and RPE were measured during each 4-minute stage of testing. In the hypohydrated condition, LAT occurred significantly earlier during exercise and at a lower absolute V(O)2, VE, respiratory exchange ratio, RPE, and blood lactate concentration. Also, the blood lactate concentration was significantly lower in the hypohydrated condition (6.7 +/- 0.8 mmol) compared with the euhydrated condition (10.2 +/- 0.9 mmol) at peak exercise. There were no differences in HR or percentage of maximum HR at LAT nor did plots of V(CO2):V(O)2 reveal differences in bicarbonate buffering during exercise between the 2 conditions. From these results, we speculate that hypohydration did not significantly alter cardiovascular function or buffering capacity but did cause LAT to occur at a lower absolute exercise intensity.