- 87 - Enhancement of Tibialis Anterior Recovery by Intermittent Se- quential Pneumatic Compression of the Legs Avi Wiener, Joseph Mizrahi (1) and Oleg Verbitsky (1) Department of Occupational Medicine, Rambam Medical Center and (1) Department of Biomedical Engineering, Technion, Israel Institute of Technology, Haifa, Israel Abstract In this study we examined the effect of Intermittent Sequential Pneumatic Compression (ISPC) of the legs on the recovery of fatigued Tibialis Anterior (TA) muscles. Eight sub- jects performed 10 min fast walking on a treadmill, followed by 2 min sustained effort of the TA (load A). Immediately afterwards they took 3 min of resting time, during which one leg was treated by ISPC (active recovery) and the opposite one served as a control (passive recovery). A second sustained effort (load B), similar to load A in intensity and duration, followed the recovery period. Surface EMG of the TA was used to monitor muscle fatigue. The results indicate that the mean power frequency (MPF) of the actively recovering TA was significantly higher than that of the passively recovering TA, irrespective of the side on which ISPC was applied. An additional interesting result was the higher MPF in the begin- ning of load B compared to that of the end of load A. However, this difference was signifi- cant in the actively recovering leg, but not so in the passively recovering leg. It was conclu- ded that ISPC treatment of fatigued muscle after a sustained effort improves its contractile capacity in comparison to passive recovery. Key words: fatigue, intermittent sequential pneumatic compression, mean power fre- quency, recovery, water evacuation. Basic Appl Myol 11 (2): 87-90, 2001 Muscle fatigue is defined as failure to maintain the required or expected force [3]. At least two mecha- nisms are involved in muscle fatigue [10]. One is re- lated to intracellular acidosis, acting directly on the myofibrils by suppressing their contractile force. The other is based on the interference with the excitation- contraction coupling process. Recovery from fatigue is sensitive to the muscular pH [13] and to the evacuation of water and metabolites in both the intracellular and the extracellular environments [14]. It is well accepted that active recovery is more effec- tive than passive recovery [1, 2]. Active recovery fa- cilitates the removal of metabolites by enhancing ve- nous blood return [1]. It has been shown that applying intermittent sequential pneumatic compression (ISPC) on the lower limbs of volunteers immediately after they had experienced muscular fatigue through isotonic cy- cling yielded a 45% improvement in their muscular per- formance. It has therefore been suggested that the "milking effect" of the ISPC, yields a significant im- provement of the venous return [15]. Other authors have shown that various devices of pneumatic compression of the legs increased maximal venous velocity (MVV) in the major veins through draining of the lower limbs [4, 8]. The efficacy of ISPC on the recovery of fatigued mus- cle by isometric exercise through systematic testing protocols and fatigue indicators has not as yet been studied. A well-established fatigue indicator at high lev- els of muscle activity is the mean power frequency (MPF) of the myo-electric signals, as recorded by EMG [12]. For instance, a sustained isometric contraction of 80% or higher of the maximal voluntary contraction (MVC) is associated with a decrease in MPF, reflecting the development of muscle fatigue. In this study we quantified the effect of ISPC on Tibi- alis Anterior (TA) recovery after a fatiguing sustained effort bout by making use of EMG fatigue indicators. We postulated that enhancing MVV in the veins of the lower limbs by ISPC would result in a faster TA recovery. This study should provide a better insight into the role of ac- celerated evacuation of water and metabolites from the muscle tissue in the recovery of fatigued muscles.