Associations Between Heart Rate and Skeletal Muscle Oxygen Saturation (SmO₂) in Upper and Lower Extremities During Self‐Paced Walking

Abstract

This study aims to determine the association between heart rate and skeletal muscle oxygen saturation (SmO₂) during 30 minutes of self‐paced walking on 4 different days. It was hypothesized that there would be a significant association between heart rate and SmO₂, as increased exercise intensity would result in increased peripheral muscle O₂ consumption and increased heart rate. Participants (age= 18‐40) were recruited from Clarkson University as part of an ongoing larger study and informed consent was signed. Heart rate was measured using a pulse oximeter after every five minute interval of the 30 minute walking period and was recorded in an online survey on surveymonkey.com. The muscle oxygen monitor (MOXY) near infrared sensors were placed on the left and right medial gastrocnemius heads as well as on the left biceps brachii muscle to record SmO₂ levels. Data was analyzed using a bivariate Pearson correlation to determine if there was a significant correlation between SmO₂ and heart rate while walking. Heart rate was negatively associated with SmO₂ in the left medial gastrocnemius head (R= ‐0.139, p= 0.044, n= 211) while there was no significant relationship seen in the right medial gastrocnemius head (p> 0.05). In the left biceps brachii muscle, there was a positive association between heart rate and SmO₂ (R= 0.148, p= 0.035, n= 204). The findings of our study suggest that as walking intensity increases, O₂ consumption in the upper and lower extremities has a weak, but significant association with heart rate. These findings suggest that as blood is shunted from the upper extremity to lower extremity to meet lower extremity demands during walking, O₂ utilization by muscles in the upper extremity is decreased. Further research is needed to elucidate how these relationships change when performing activities that require both upper and lower extremity muscles as well as with varying intensities of exercise.