Journal of Exercise, Sports & Orthopedics

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Authors: Daniel J Leong, Hui B Sun

Osteoarthritis (OA) is a degenerative joint disease and a leading cause of adult disability. The etiology of OA is not clear, but common risk factors for developing OA include age, joint injury, mechanical overuse, and obesity. Exercise is the most common non-pharmacologic therapy prescribed to patients with osteoarthritis. The Arthritis Foundation promotes an exercise program involving low-impact physical activity, and participants have reported less pain and fatigue, and increased strength. Clinical trials of patients with OA report physical activities including aerobic exercise, stretching/flexibility, endurance training, aquatic exercise, and muscle strengthening lead to improvements in pain relief, body weight, and metabolic abnormalities [1]. Factors which are critical to successful outcomes of exercise programs include performing exercises at an appropriate intensity and duration, and long-term adherence to exercise programs. Individualized exercise programs are important to educate patients to avoid exercises which may be harmful to injured joints (e.g. high impact activities). Patient monitoring or prescription of exercises which the patients find enjoyable may promote long-term adherence to an exercise program.

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Authors: Adriano Detoni Filho*, Michele Guiramand, Paulo Lague Sehl, Gabriela Tomedi Leites and Rafael Reimann Baptista

Young rhythmic gymnastics (RG) athletes engage in long training sessions that can lead to dehydration, especially on very hot days. Hydration status can affect the sporting performance and health maintenance of these young gymnasts. To evaluate the sweat volume, fluid balance and perceptual responses of young female RG athletes during a training session in the heat, fourteen female RG athletes (11.3±2.6 years) with a body fat percentage of 17.35±4.85% participated in this study. Body weight was measured and a urine sample collected for color analysis, both before and after the training session. The workout lasted 2.5 h in environmental conditions of between 29 °C and 50% relative humidity (RH), and 30 °C and 59% RH. Water was made available for consumption ad libitum and sweat volume was calculated from the change in body weight, corrected for water intake. The rate of perceived exertion, thermal sensation, thermal comfort, and irritability were measured every 30 minutes using categorical scales. Sweat volume was 1146.6±412.6 mL and water consumption was 825.2±368.1 mL. The negative fluid balance was between 1-2% in 50% and 1% in 42.8% of the athletes. Twelve athletes began the training session hypohydrated (urine color between 3 and 7), and 92.3% were hypohydrated after training (urine color between 4 and 6). There was an increase in thermal sensation (8±1) and discomfort (3±1) over the course of the workout. The RG athletes were unable to adequately replace their fluid losses, despite water being available for drinking ad libitum, which may reflect on the perceptual responses to heat. Keywords: Sweating; Hydration; Exercise in the heat; Gymnastics; Children

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Authors: Vinzenz von Tscharner

During sport activities the gastrocnemius muscle must be activated in an orderly way to fulfill the tasks of force development, control of stability. The fascicles do not span the whole muscle and there are multiple motor units that have to be coordinated. Failure to do so results in excessive or uncoordinated forces in the joints. Thus it is important to be able to observe how synchronization of motor units changes under load. The present work is a first introduction to the possibilities of measuring the correlation of raw EMG-currents of four adjacent surface electrodes attached to the proximal region of the medial gastrocnemius muscle. In summary, the results showed and confirmed the hypotheses that the EMG-signals were correlated, that correlation was present when standing on the forefoot (tiptoe position) but increased during a repetitive calf-rising movement. The EMG-signals of adjacent electrodes could be decomposed into a reverse- and an in-phase component. The median frequencies decreased with increasing synchronization and were larger in the reverse-phase component than in the in-phase component. The results can be explained by a task dependent synchronization of motor units. Thus the method offers the possibility to study the effect of synchronization at higher levels of muscle activity. Keywords: Electromyograms; Trans-impedance amplifier; Current amplifier; Correlation of EMG signals