Journal of Exercise Science & Fitness

Stability of RPE Increase During Repeated Intermittent Sprints

2010-06-01

The current investigation examined the potential teleoanticipatory effect on perceptual response during repeated bouts of maximal sprint work. To determine the consistency of ratings of perceived exertion (RPE) increase during identical exercise bouts following variable recovery periods, 16 (8 men, 8 women) participants completed four separate trials of repeated maximal sprinting on 4 separate days utilizing different recovery periods. Following completion of the baseline trial, participants were given variable, counter-balanced recovery periods of 24, 48 and 72 hours, whereupon they repeated the intermittent exercise protocol. To determine the degree of similarity among trials, each individual's rate of RPE progression during each cycle of eight sprints throughout the recovery trials were compared to the rate of progression during the baseline exercise session. A series of 4 (trial) × 3 (cycle of sprints) repeated measures ANOVA were performed to identify significant main effects between trials and among cycles while session RPE was analyzed using one-way repeated measures ANOVA. Fisher's least significant difference post-hoc procedures were performed to identify where significant differences occurred when appropriate. Results revealed an inconsistency in the stability of RPE across repeated bouts of sprint exercise, with at least 50% of individuals having a substantial difference in RPE (i.e. ± 1 unit change) in at least one subsequent trial. These variations in perceptual responses were observed despite a concomitant stability of physiological and performance responses between sessions. Results suggest that rate of RPE increase correspond more closely to increased or decreased physiologic strain than to an anticipatory, feed-forward mechanism following variable recovery durations.

Effects of Acute Bouts of Swimming Exercise on AMPKα2 Expression in Mouse Skeletal Muscle

Yang Wang, Ying Zhang — 2010-06-01

The 5′-AMP-activated protein kinase (AMPK) is a multisubstrate serine/threonine protein kinase that is ubiquitously expressed and functions as an intracellular fuel sensor activated by depletion of high energy phosphate compounds. The a2 isoform is by far the most abundant in skeletal muscle, representing at least 66% of total AMPK activity. The purpose of this study was to determine the effects of the different exercise (swimming) durations on AMPKα2 gene and protein expression, and the relationships between the expression of AMPK and blood glucose and muscle glycogen. C57 mice were divided into three groups: a sedentary control group, a 90-minute swimming exercise group, and an exhaustive swimming exercise group. AMPKα2 gene and protein expression in the quadriceps muscle were measured separately by real-time quantitative PCR and Western immunoblot after the swimming exercise. Blood glucose and muscle glycogen were also measured at the same time. The results showed that 90-minute and exhaustive swimming exercise induced significant increases in skeletal muscle AMPKα2 gene and protein expression compared to in the control group, and AMPKα2 expression was higher after exhaustive swimming than after 90-minute swimming exercise. There was a significant negative correlation between AMPKα2 expression and blood glucose level. The high AMPKα2 gene and protein expression induced by exercise might be one of the reasons for blood glucose reduction, but not the key factor which regulates the degradation of muscle glycogen during swimming exercise.

Fundamental Movement Skills Among Filipino Children With Down Syndrome

Catherine M. Capio, Esmerita R. Rotor — 2010-06-01

Impairments among individuals with Down syndrome (DS) include low muscle tone, decreased strength, poor postural control, and balance. Congenital heart defects and obesity are also common. In order to keep fit and prevent further complications, participation in physical activities is encouraged. Fundamental movement skills (FMS) are necessary in sports and physical activity participation. There is a research gap in the area of FMS development among children with DS, particularly for Asian populations. This study aimed to describe FMS among a sample of Filipino children with DS. A descriptive observational study was conducted using a standardized protocol and criterion-referenced assessment procedure. The following variables were investigated: overhand throwing, catching, standing long jump, kicking, and running. Each variable was analyzed in terms of body components. The participants were grouped into three age groups: 3–5, 6–8, and 9–12 years old. Data were analyzed using Kruskal-Wallis to test significant differences in the skills ratings of the age groups, with alpha level set at 0.05. The results showed significant differences in the skill components except leg-foot preparation and leg-foot action in kicking, arm preparation in catching, arm action in kicking, and arm preparation in standing long jump. The observed components that did not appear to have significant changes were related to balance and coordination deficits, as well as weakness of the trunk and legs. This may imply that physiotherapists need to address impairments in children with DS, focusing on coordination and balance problems as well as strengthening of trunk and legs.

Meal Composition and Iron Status of Experienced Male and Female Distance Runners

Sandra Anschuetz, Carol D. Rodgers, Albert W. Taylor — 2010-06-01

This study compared the iron status of middle-distance runners consuming meals providing low-medium iron availability (LMIA) or medium-high iron availability (MHIA), and determined the effect of a 4-week intervention on iron status in LMIA participants. Seventeen university-aged competitive runners and eight inactive controls participated. Mean serum ferritin levels were significantly greater in the MHIA group (58.7 ± 9.7ng·mL−1) than in the LMIA group (43.6 ± 10.9 ng·mL−1). Significant (p < 0.05) correlations were noted between absorbable dietary iron and serum iron (r = 0.639), total iron binding capacity (r = −0.636) and hemoglobin (r = 0.523). The mean absorbable dietary iron was significantly greater following the intervention in LMIA males (Test 1, 0.97 ± 0.3 mg·day−1; Test 2, 1.54 ± 0.5 mg·day−1; p < 0.05). Dietary advice did not improve iron status. These data suggest that meal composition may influence the amount of iron available for absorption and for maintaining iron status over time.

Gastric Emptying Rate of Young Cyclists by Magnetic Resonance Imaging: Three Case Studies

2010-06-01

Gastric emptying rate during exercise has been documented in adult athletes, but not in younger athletes because of the utilization of invasive techniques. However, magnetic resonance imaging (MRI) is a noninvasive alternative. The aim of this study was to pilot the sequencing of MRI to a typical fluid intake strategy, in order to assess the viability of the procedure. Therefore, we compared the gastric emptying rate of water and a carbohydrate drink in three well-trained 17-year-old cyclists using MRI. Each participant cycled 4 bouts of 15 minutes each at moderate intensity followed by a ∼15-minute time trial. Water or carbohydrate drinks were distributed in amounts of 200–250 mL. After an initial baseline MRI scan, cyclists ingested the first drink, cycled 15 minutes, followed by an MRI scan to assess remaining gastric volume. This feeding-exercise-scanning protocol was repeated thereafter. Relative to the initial volume at the start of the time trial, 69% and 72% of water and carbohydrate emptied during the time trial. MRI appears to be a feasible technique to assess gastric emptying rates in youth cyclists.

A Two-level Model of Motor Performance Ability

Lena Lämmle, Susanne Tittlbach, Jennifer Oberger, Annette Worth, Klaus Bös — 2010-06-01

For many years, motor performance ability (MPA) has been viewed as a multidimensional construct consisting of such specific components as endurance, strength, coordination, and flexibility. This report examines whether these assumed structures of MPA can be found empirically in children and adolescents. The Motoric-Module, conducted between 2003 and 2006 in Germany for the differentiated measurement of MPA from ages 6 to 17 (N = 2,840), made use of an eight-item performance test battery. This test battery was assumed to assess the five motor dimensions of endurance, strength, coordination under time pressure, coordination under precision demands and flexibility. A two-level model of MPA with these five motor dimensions as first order factors could be confirmed using confirmatory factor analysis. The path coefficient (p < 0.001) describing the direct effect from MPA to strength was 0.97, followed by the effect from MPA to coordination under precision demands (a = 0.73). The coefficient relating from MPA to coordination under time pressure was less (a = 0.64) and the lowest loadings shown for MPA are demonstrated for endurance (a = 0.36) and flexibility (a = 0.23). The first order factors showed significant direct effects on each of the observed variables. Therefore, a differentiated diagnosis of MPA in children and adolescents is possible. This is important for health care.

Effect of β-hydroxy-β-methylbutyrate Supplementation During Energy Restriction in Female Judo Athletes

Wei Hung, Tsung-Han Liu, Chung-Yu Chen, Chen-Kang Chang — 2010-06-01

Supplementation of β-hydroxy-β-methylbutyrate (HMB) has been suggested to help increase muscle mass or reduce body fat in resistance-trained subjects and patients in catabolic states. The aim of this preliminary study was to investigate the effect of oral supplementation of 3 g·day−1 HMB for 3 days on body composition and exercise performance in well-trained female judo athletes during energy restriction. Eight female judo athletes were matched for body weight and divided into HMB and control groups. All subjects consumed food containing 20kcal·kg−1 with carbohydrate 3.6g·kg−1, protein 1.33g·kg−1, and fat 0.03g·kg−1 each day. Body weight and body fat percentage were significantly decreased in the HMB group, but remained unchanged in the control group after the study period. Muscle mass and the anaerobic performance of the lower and upper body were unchanged in both groups. The HMB group showed significant increases in total cholesterol, blood urea nitrogen, and uric acid after the study period. The control group did not show any significant changes in all blood parameters. This study suggested that short-term supplementation of HMB during energy restriction may help to reduce body fat but has no effect on lean body mass or exercise performance in female athletes.

Effects of Short-Term Resistance Training on Serum Leptin Levels in Obese Adolescents

2010-06-01

The purpose of this study was to examine the effects of a short-term resistance training program on serum leptin concentrations in obese adolescents. Eighteen Chinese obese adolescents participated in the supervised weight management program. Resistance training was conducted three times a week on alternate days for 6 weeks. Body composition [body fat mass (FM) and body lean mass (LM)] determined by dual-energy X-ray absorptiometry, muscle strength and leptin, insulin and glucose were measured before and after training. Subjects demonstrated significantly improved strength of leg, chest and bicep under conditions of stability in weight, FM and LM. There were positive correlations between leptin and body mass index, FM, %FM, waist girth and hip girth, and negative correlations between leptin and %L M at the resting state before and after 6 weeks of resistance training. No significant relationship was found between leptin concentration and the parameters of muscular strength or concentrations of insulin and glucose. Compared to pre-training values, serum leptin levels were not significantly altered, while relative leptin (leptin/FM) decreased significantly after the short-term resistance training. These results indicate that short-term resistance training enhances muscle strength but does not alter leptin levels in obese adolescents with weight and FM stability. The results also suggest that 6 weeks of resistance training decreases the requirement of leptin per unit of FM and improves leptin sensitivity in obese adolescents.