Craig O. Mattern

Peer 2 Peer: Efficacy of a Course-Based Peer Education Intervention to Increase Physical Activity Among College Students

Abstract 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.

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.

Physical Self-Concept and Strength Changes in College Weight Training Classes

Physio logical consequences of participation in a strength training program have been established. Overloading specific muscles over time will result in predictable and often substantial increases in muscular strength (Wilmore, 1974). Psychological attributes, such as self-concept, can also be modified through exercise (Fox, 2000; Sonstroem, 1998), and there is evidence that strength training promotes the greatest changes in selfperceptions (Fox, 2000). The theoretical model of self-concept with the most empirical support is a multidimensional hierarchical model (Marsh, 1997;Shavelson, Hubner, & Stanton, 1976), which includes global self-concept/self-esteem at the apex with psychosocial perceptions progressing down from general to specific. This model has been applied to the physical self-concept domain and has influenced the development of models such as the Exercise and Self-Esteem Model (ESEM; Sonstroem, & Morgan, 1989) to explain how exercise can affect self-concept and self-esteem. According to the ESEM, exercise behavior can affect selfperceptions by changing specific self-efficacies, which influence perceived physical competence and acceptance and, ultimately, more global physical self-concept and self-esteem (Sonstroem & Morgan, 1989). The skill development hypothesis also supports exercise affecting self-perceptions by increases in physical fitness augmenting perceived physical competence, which similarly in-

Influence of Racial Origin and Skeletal Muscle Properties on Disease Prevalence and Physical Performance

AbstractSkeletal 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.

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.