Quadriceps-hamstring EMG activity during functional, closed kinetic chain exercise to fatigue.

It has been hypothesized that the ability of the neuromuscular system to co-contract muscles for joint stabilization may be impaired during the development of fatigue. The purpose of this study was to examine muscle activation of the quadriceps and hamstring muscles during a prolonged closed kinetic chain exercise, the forward lunge. Eight males and two females [mean (SD) age 26.0 (2.3) years, height 177.2 (13.6) cm, body mass 82.8 (17.1) kg] with no prior knee pathology volunteered for this study. Subjects performed repeated forward lunges onto their dominant leg at the cadence of one full lunge cycle every 2 s, until the point of volitional failure. Digital switches were positioned to record foot-strike and knee-strike of the lunge leg at the midpoint of the lunge, as well as heel-strike upon return to stance. During the lunge performance, surface electromyographic (EMG) signals of the vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), and semitendinosus (ST) muscles of the supporting leg were measured. Heart rate was also monitored every 30 s during the performance. All EMG data were full-wave rectified, partitioned into up and down phases, and integrated over the entire exercise period. The results demonstrated a significant increase in activation of the VL, VM, and BF during performance of the forward lunge to volitional failure (P < 0.05). No significant increase was shown for the ST. Heart rate increased significantly over the course of the lunge. These findings suggest that activation of the VL, VM, and BF muscles occurs as a unit during performance of the forward lunge during both concentric and eccentric lunge phases.

Noninvasive positive-pressure ventilation in chronic obstructive pulmonary disease.

Interest in noninvasive positive-pressure ventilation both as an alternative to intubation and mechanical ventilation and as a unique therapy has grown over recent years. Clinical and patient acceptance is highest in neuromuscular deficits, but supporting evidence for its use in chronic obstructive pulmonary disease is highly dependent on the application. This review considers the clinical implementation of noninvasive positive-pressure ventilation in acute respiratory failure, as a postextubation weaning alternative, in stable severe hypercapnic chronic obstructive pulmonary disease, in overlap syndrome, and for nocturnal oxygen desaturation. Some applications are well supported, leading to a cautious recommendation for its utilizatip4, whereas for others evidence is starkly conflicting. The clinical efficacy of noninvasive positive-pressure ventilation is vastly dependent on equipment, equipment-patient interface, pressure settings, physician's bedside manner, and experience of the center. Interpretation of the studies must take into account the foregoing factors along with the various ventilatory techniques and differing primary outcome measures. Generalizations can be made regarding indications and contraindications, but this is an area rife with exceptions. The subtle message from the clinical studies describes the importance of the clinical art applied from the palette of science and technology.