Muscle Oxygenation of the Paretic and Nonparetic Legs During and After Exercise in Chronic Stroke: Implications for Mobility.

INTRODUCTION
Oxygen delivery and demand are reduced in the paretic leg of post-stroke individuals. However, it is unknown how muscle oxygenation, the balance between delivery and utilization of oxygen at the muscle is altered post-stroke during aerobic exercise and how it relates to mobility.


OBJECTIVES
The objective of this study was to monitor muscle oxygenation changes between the paretic and nonparetic legs of post-stroke individuals during treadmill exercise and the six-minute walk test and analyze the association with mobility.


DESIGN
Cross-sectional study.


SETTING
Cardiac rehabilitation program.


PATIENTS
Eleven male subjects were enrolled in the study. Ten male subjects (30.8±4.1 months post-stroke; age 63.9±13.9 years) with hemiparetic gait pattern finished the study.


INTERVENTIONS
Not applicable.


MAIN OUTCOME MEASURES
Muscle oxygenation was measured with near-infrared spectroscopy placed on the vastus lateralis of each leg during treadmill exercise at the first ventilatory threshold and during a six-minute walk test.


RESULTS
The desaturation slope during treadmill exercise was significantly steeper (p=0.047) in the paretic (-0.7±0.6%/s) compared to the nonparetic leg (-0.3±0.2%/s). There was no other significant difference between legs. The six-minute walk test distance was not correlated with six-minute walk test muscle oxygenation in either leg (paretic: r=0.20, p=0.590; nonparetic: r=0.42, p=0.232).


CONCLUSIONS
At the onset of treadmill exercise, the paretic leg was unable to effectively match oxygen demand and extraction as well as the nonparetic leg, suggesting the need for an immediate cardiovascular warmup prior to initiating moderate intensity exercise in this population. Since the exercise desaturation rate is thought to indicate increased anaerobic metabolism and lactate production, efforts to delay rapid desaturation could improve sustainability of activities of daily living and exercise.