Compression garments reduce muscle movement and activation during submaximal running

Purpose The purpose of this study was to investigate the effectiveness of sports compression tights in reducing muscle movement and activation during running. Methods A total of 27 recreationally active males were recruited across two separate studies. For study 1, 13 participants (mean ± SD = 84.1 ± 9.4 kg, 22 ± 3 yr) completed two 4-min treadmill running bouts (2 min at 12 and 15 km·h-1) under two conditions: a no-compression control (CON1) and compression (COMP). For study 2, 14 participants (77.8 ± 8.4 kg, 27 ± 5 yr) completed four 9-min treadmill running bouts (3 min at 8, 10, and 12 km·h-1) under four conditions: a no-compression control (CON2) and three different commercially available compression tights (2XU, Nike, and Under Armor). Using Vicon 3D motion capture technology, lower limb muscle displacement was investigated in both study 1 (thigh and calf) and study 2 (vastus lateralis + medialis [VAS]; lateral + medial gastrocnemius [GAS]). In addition, study 2 investigated the effects of compression on soft tissue vibrations (root-mean-square of resultant acceleration, RMS Ar), muscle activation (iEMG), and running economy (oxygen consumption, VO2) during treadmill running. Results Wearing compression during treadmill running reduced thigh and calf muscle displacement as compared with no compression (both studies), which was evident across all running speeds. Compression also reduced RMS Ar and iEMG during treadmill running, but it had no effect on running economy (study 2). Conclusion Lower limb compression garments are effective in reducing muscle displacement, soft tissue vibrations, and muscle activation associated with the impact forces experienced during running

Quadriceps Muscle Fatigue Reduces Extension and Flexion Power During Maximal Cycling

Purpose: To investigate how quadriceps muscle fatigue affects power production over the extension and flexion phases and muscle activation during maximal cycling. Methods: Ten participants performed 10-s maximal cycling efforts without fatigue and after 120 bilateral maximal concentric contractions of the quadriceps muscles. Extension power, flexion power and electromyographic (EMG) activity were compared between maximal cycling trials. We also investigated the associations between changes in quadriceps force during isometric maximal voluntary contractions (IMVC) and power output (flexion and extension) during maximal cycling, in addition to interindividual variability in muscle activation and pedal force profiles. Results: Quadriceps IMVC (−52 ± 21%, P = 0.002), voluntary activation (−24 ± 14%, P \u3c 0.001) and resting twitch amplitude (−45 ± 19%, P = 0.002) were reduced following the fatiguing task, whereas vastus lateralis (P = 0.58) and vastus medialis (P = 0.15) M-wave amplitudes were unchanged. The reductions in extension power (−15 ± 8%, P \u3c 0.001) and flexion power (−24 ± 18%, P \u3c 0.001) recorded during maximal cycling with fatigue of the quadriceps were dissociated from the decreases in quadriceps IMVC. Peak EMG decreased across all muscles while inter-individual variability in pedal force and EMG profiles increased during maximal cycling with quadriceps fatigue. Conclusion: Quadriceps fatigue induced by voluntary contractions led to reduced activation of all lower limb muscles, increased interindividual variability and decreased power production during maximal cycling. Interestingly, power production was further reduced over the flexion phase (24%) than the extension phase (15%), likely due to larger levels of peripheral fatigue developed in RF muscle and/or a higher contribution of the quadriceps muscle to flexion power production compared to extension power during maximal cycling

Effects of Oxygen Stoichiometry on Structure And Properties in Ba//2ycu//3O//X. .

Results of a series of studies on the oxygen stoichiometry in Ba//2YCu//3O//x, 6. 0 less than equivalent to x less than equivalent to 7. 0, are reported. The structure at x equals 7 contains layers of corner-shared, square pyramidal copper and chains of square planar copper. Oxygen is removed from the chains leaving two-fold coordinate copper at x equals 6. Superconductivity is optimal for x approximately equals 7 and for x equals 6 the material is a semiconductor. A valence description ascribes Cu** plus **2 to the Cu in the layers for all x with the Cu in the chains going from Cu** plus **3 at x equals 7 to Cu** plus **1 at x equals 6. A model for twinning based on oxygen defects similar to those in Ba//2YCu//3O//6 is discussed