Effects of the Off-Loading Brace on the Activation of Femoral Muscles: A Preliminary Study

OBJECTIVE: To provide the off-loading knee brace was designed relief for the pain associated with osteoarthritis by reduce loads on the degenerative compartment of the knee. This study examined the effects of the off-loading knee brace on activation of femoral muscles during squatting, slow and fast walking exercise in healthy young individuals. METHOD: Ten healthy male subjects without a history of knee pain were recruited. Each subject was asked to do squatting, slow and fast walking exercises with a brace secured to the dominant leg. The same exercises were repeated without the brace. Surface electromyographic (sEMG) data was collected from the vastus medialis oblique (VMO), vastus lateralis (VL) and biceps femoris (BF) muscles from the dominant side of the leg. All dynamic root mean squre (RMS) values of sEMG were standardized to static RMS values of the maximal isometric contraction and expressed as a percentage of maximal activity. RESULTS: We found that VMO activity was significantly decreased with application of the off-loading knee brace during squatting and fast walking exercise. However there were no significant differences in VMO activity with application of the off-loading knee brace during slow walking exercise. CONCLUSION: These results suggest that the external moment of the brace which effectively stabilized the patella in the movement in which the knee joints become relatively unstable. The brace could be useful in the short term, but for long-term use, weakening of the VMO is predicted. Therefore the program of selective muscular strength strengthening for the VMO should be emphasized.

Validity of Two Kinds of Physical Activity Tracker for Measuring Total Calorie Expenditures and Activities above Moderate Intensity

OBJECTIVE: To evaluate the validity of two kinds of physical activity trackers (PAT) during treadmill exercise. METHOD: 14 healthy people performed cardiopulmonary exercise test by means of Bruce protocol. The omnidirectional PATs were placed onto the right wrist and ankle, and the temperature sensing PATs were placed onto the right arm and lower leg. Simultaneous measurement of body motion was continuously recorded during cardiopulmonary exercise test. Then we checked total calorie expenditure and duration above moderated intensity activity (>3 METs) from each PATs and gas analyzer. RESULTS: Total calorie expenditures of PAT were significantly underestimated than gas analyzer, except the temperature sensing PAT applied onto the leg, but all of them showed significant correlation. The duration above moderate intensity activity of the PAT did not show significant difference comparing with gas analyzer, except the omnidirectional PAT applied onto the arm, but all of them showed significant correlation. CONCLUSION: Both omnidirectional PATs and temperature sensing PATs could estimate the total calorie expenditure and the duration above moderate intensity activity. But it is necessary to apply exercise-specific protocol to PAT to enhance the accuracy of estimating energy expenditure during periods of exercise.