Journal of Exercise Science & Fitness

Effects of Non-Wingate-based High-intensity Interval Training on Cardiorespiratory Fitness and Aerobic-based Exercise Capacity in Sedentary Subjects: A Preliminary Study

Tom K. Tong, Pak Kwong Chung, Raymond W. Leung, Jinlei Nie, Hua Lin, Jun Zheng — 2011-12-01

This study examined two hypotheses: (1) a non-Wingate-based high-intensity interval training protocol of 20×30-second cycle exercise at 120% of peak aerobic power interspersed with 60-second recovery per session, 3 sessions per week for 6 weeks, can enhance cardiorespiratory fitness and aerobic-based exercise capacity; and (2) proportional-assist ventilation (PAV) can augment interval training intensity, and, in turn, enhance the adaptations to the training in sedentary and mild obese individuals. Sixteen subjects were paired up and assigned into an interval training (IT) group or IT plus PAV (IT + PAV) group. During the 6-week interval training program, the increase in training intensity was not different between the IT and IT + PAV groups (p > 0.05). Nevertheless, significant improvements were found in the peak work rate and peak O2 during the post-training incremental cycling test in both groups. Moreover, the limit of tolerance during the post-training constant-load cycling test (70% of pre-training peak aerobic power) was enhanced, while blood lactate accumulation, heart rate, ratings of breathing discomfort, and perceived exertion at the iso-time point of the pre-training test at exhaustion were reduced (p < 0.05). The interaction effect on the change in each variable between the two groups was not significant (p > 0.05). In conclusion, the 6-week non-Wingate-based high-intensity interval training protocol was preliminarily found to enhance cardiorespiratory fitness and aerobic-based exercise capacity in sedentary and mild obese subjects. The provision of PAV during the interval training did not augment training intensity and subsequent aerobic adaptations.

Monitoring Children's Physical Activity With Pedometers: Reactivity Revisited

John T. Foley, Michael W. Beets, Bradley J. Cardinal — 2011-12-01

Thirty-two children (aged 7–11 years) were monitored for 4–5 consecutive days under two randomly assigned crossover treatment/non-treatment conditions (minimum of 2 days for each condition): (1) accelerometer (i.e., control or covert monitoring); and (2) accelerometer and pedometer (i.e., treatment or known monitoring). Participants were informed the accelerometer was measuring “time”—serving as the blinding condition. Paired analyses were performed between conditions for four time segments (warm-up and three activity units). A significant difference during the warm-up was observed. No other changes in activity levels were present. The findings suggest that during unrestricted play, children increase their activity when being monitored.

An Examination of the Effectiveness of an 8-week Bikram Yoga Program on Mindfulness, Perceived Stress, and Physical Fitness

Zoe L. Hewett, Lynda B. Ransdell, Yong Gao, Linda M. Petlichkoff, Shelley Lucas — 2011-12-01

Previous research reports positive effects of yoga on health. The physical and psychological outcomes of participation in Bikram yoga are under-researched despite its increasing popularity, and this type of yoga may be significant with regards to stress management due to its unique method of practice. This study was designed to assess changes in levels of mindfulness, perceived stress, and physical fitness after participation in an 8-week Bikram yoga program. Fifty-one participants aged 20–54 years (mean, 31.57 years) were recruited by word of mouth from a large university located in the Northwestern United States. Participants attended a minimum of 20 Bikram sessions over 8 weeks. Changes in mindfulness (Five-Facet Mindfulness Questionnaire), perceived stress (Perceived Stress Scale), and physical fitness (resting heart rate, 1-mile walk, sit-and-reach, total-body rotation, and single-leg balance) were measured. Eight weeks of Bikram yoga improved mindfulness, perceived stress, cardiorespiratory endurance, flexibility and balance (p < 0.01). Mindfulness was negatively correlated with perceived stress (r=−0.43, p < 0.01) and resting heart rate (r=−0.30, p < 0.05). The results show that Bikram yoga positively affected psychological and physical health in the sample population. This information can be used to further the understanding of mind-body based programs, and how Bikram yoga may give people the tools to decrease perceived stress, potentially having an effect on chronic stress-related illnesses.

Effect of Cycling Exercise at Different Pedal Cadences on Subsequent Muscle Strength

2011-12-01

The main purpose of this study was to compare the effects of previous high-intensity aerobic exercise at 50 and 100 rev · min−1 on subsequent strength determined through maximal repetitions (RM) and countermovement jump (CMJ). Thirteen physically active males (age, 23.0 ± 3.7 years; weight, 77.1 ± 8.8 kg; height, 179.3 ± 4.0 cm; %body fat, 14.3 ± 2.9%) performed the following procedures on different days: (1) incremental test on cycle ergometer to determine the onset of blood lactate accumulation at 50 and 100 rev · min−1; (2) three sets of RMs with the load corresponding to 10 RM in leg press 45° (LC); (3) three sets of 10 maximal CMJ in contact plate (JC); (4) four trials of 30 minutes at the onset of blood lactate accumulation obtained at 50 and 100 rev · min−1, followed by three sets of RMs with 10 RM load (L50 and L100, respectively) or three sets of maximal CMJ (J50 and J100, respectively). Strength was compromised at 100 rev · min−1 (L100 = 22.6 ± 6.0 vs. LC = 30.4 ± 1.5 repetitions) in leg press, while CMJ height was reduced at 50 rev-min−1 (J50 = 29.2 ±3.0 vs. JC = 31.7 ± 2.9 cm). The reduction in number of repetitions at L100 (26%) was significantly higher than CMJ height at J50 (8%). In conclusion, the extent of strength loss after high-intensity aerobic exercise can be dependent on both pedal cadence and strength test conditions. When aerobic cycling exercise precedes strength training, it may be beneficial to use low pedal cadences to minimize strength loss.

Effect of Textile Hygroscopicity on Stratum Corneum Hydration, Skin Erythema and Skin Temperature During Exercise in the Presence of Wind and No Wind

Kerry Atkins, Martin Thompson — 2011-12-01

This crossover designed study examined the influence of textile hygroscopicity on skin temperature responses during 30 minutes of continuous cycling exercise at 60% O2peak in a thermoneutral environment (20°C and 50% relative humidity) in the convective airflow presence of forced convection (4.5 ± 0.2m · s−2) and under minimal convective airflow conditions. Ten well-trained male road cyclists completed two wear trials at random in the forced convection and minimal convective airflow condition wearing a long-sleeved cycling jersey that had a split design with a strongly hygroscopic (SH) fabric (wool) on one half and a weakly hygroscopic (WH) fabric (polyester) on the other half of the garment. The cyclists' mean age was 31±5 years, mean height was 1.81 ± 0.05 m, mean body mass was 83.55 ± 10.89 kg, and mean body surface area was 2.04 ± 0.14 m2. The previously reported actions of SH fibers increasing skin temperature through the evolution of sorption heat following moisture absorption, and subsequent elevation in fabric temperature, was assessed. An effect of WH fibers to impact skin temperature through increasing stratum corneum hydration, producing more skin-to-fabric contact and skin erythema, was also investigated. Similar physiological responses in the skin, including temperature, sweating, stratum corneum hydration (inferred from skin resistance) and erythema (indicated by luminous flux), were found for both the SH and WH fabrics under wind and no wind conditions. In conclusion, the textile hygroscopicity of the test garment was not found to significantly influence skin temperature during moderate-intensity cycling exercise for 30 minutes in a thermoneutral environment under minimal wind conditions and in the presence of forced convection.

Disordered Eating Attitudes in Relation to Anxiety Levels, Self-esteem and Body Image in Female Basketball Players

Maria Michou, Vassiliki Costarelli — 2011-12-01

The purpose of the current study was to explore the possible differences in disordered eating (DE) attitudes, components of body image, self-esteem and anxiety levels in a group of female basketball players. A total of 154 women, 74 Greek basketball players (national and international level) and 80 women who were non-athletes, were recruited. Participants completed the following questionnaires: the Eating Attitudes Test (EAT-26), the Multidimensional Body–Self Relations Questionnaire (MBSRQ), the State-Trait Anxiety Inventory (STAI), and Rosenberg's Self-Esteem Scale (RSE). Analysis revealed that in the group of 154 young women (athletes and non-athletes), the women with DE attitudes had higher levels of anxiety and scored significantly more in components of the body image questionnaire (MBSRQ) such as appearance orientation (p = 0.002), health evaluation (p = 0.026), health orientation (p < 0.001), and illness orientation (p = 0.003). In addition, 11% of the basketball players and 15% of the non-athletes demonstrated DE attitudes. However, the differences between the two groups were not significant. The analysis of specific components of the body image questionnaire (MBSRQ) revealed that athletes scored significantly higher in fitness orientation (p = 0.021) and fitness evaluation (p = 0.019). There were no significant differences in the STAI and RSE results between athletes and non-athletes. The prevalence of DE attitudes in female basketball players was slightly lower than that in non-athletes, but the difference was not statistically significant. More studies specifically designed to investigate DE attitudes in females involved in team sports, such as basketball, are needed.

Glutamine Supplementation in Recovery From Eccentric Exercise Attenuates Strength Loss and Muscle Soreness

Brian Street, Christopher Byrne, Roger Eston — 2011-12-01

The purpose of this study was to examine the effect of glutamine supplementation on indices of recovery following eccentric exercise. In a randomized single-blind placebo-controlled design, 15 physically active males (mean age, 21 ± 1.5 years; mean height, 1.81 ± 0.07 m; mean body mass, 78.4 ± 9.2 kg) were assigned to a control or glutamine intervention group. Each participant performed 100 drop jumps from 0.6m followed by ingestion of 0.3 g · kg−1 body mass of maltodextrin mixed with 750 mL of distilled water and lemon flavoring (Control) or with an additional 0.3 g · kg−1 L-glutamine (Glutamine) at 0, 24, 48, and 72 hours post-exercise. Knee-extensor concentric peak torque at angular velocities of 0.52 and 3.14 rad · s−1, perceived muscle soreness, and plasma creatine kinase activity were measured at 0, 1, 24, 48, 72, and 96 hours post-exercise. L-glutamine supplementation resulted in a greater preservation of peak torque over the 96-hour measurement period at both 0.52 rad · s−1 (Control, 75 ± 16%; Glutamine, 85 ± 15% of pre-exercise values, p = 0.03) and 3.14 rad · s−1 (Control, 79 ± 16%; Glutamine, 90 ± 12%, p = 0.01). Muscle soreness was significantly lower over 96 hours with L-glutamine supplementation (Control, 4.6 ± 2.5 units; Glutamine, 3.6 ± 2.5 units, p = 0.03). L-glutamine supplementation did not affect the magnitude or temporal nature of the creatine kinase response. As a therapeutic intervention, glutamine supplementation was effective in attenuating strength loss and muscle soreness following eccentric exercise-induced muscle damage.

Reactive Oxygen Species and p38 Mitogen-activated Protein Kinase Mediate Exercise-induced Skeletal Muscle-derived Interleukin-6 Expression

Xuelin Zhang, Minhao Xie, Yi Yan, Yanfang Wu, Jianxing Xu — 2011-12-01

Interleukin-6 (IL-6) is a pleiotropic cytokine secreted by many different cell types, and skeletal muscle is an important source of IL-6 during exercise. Here, we studied the effects of glucose deprivation in vitro on skeletal muscle-derived IL-6 expression and release in C2C12 myocytes, as well as its regulation by p38 mitogen-activated protein kinase (p38MAPK) and reactive oxygen species (ROS). C2C12 myotubes were cultured in DMEM medium containing 4.5 g · L−1 glucose (glucose control, GC) or DMEM medium containing no glucose (glucose deprivation, GD) for 0, 6, 12, 18 and 24 hours, and then incubated with 10mM NAC (a ROS scavenger) or 10 μM SB203580 (a p38MAPK inhibitor) under either GC or GD conditions for 24 hours. IL-6 expression levels were subsequently analyzed using RT–PCR, and IL-6 protein levels in the medium were measured using ELISA. Glucose deprivation significantly enhanced IL-6 expression at 18 and 24 hours compared to the glucose control, and caused IL-6 protein levels to increase significantly over the entire 24-hour measurement period. The ROS scavenger NAC inhibited the glucose deprivation-induced release of IL-6 protein almost completely, while the p38MAPK inhibitor SB203580 inhibited glucose deprivation-induced IL-6 protein release to a lesser extent. Our study suggests that glucose deprivation in C2C12 myocytes induces IL-6 expression and release, and that this IL-6 release is mainly mediated via ROS signaling. Skeletal muscle-derived IL-6 may thus play an important role in energy metabolism during exercise.