Myocardial load at 30% and 50% of Maximal Voluntary Isometric Contraction in healthy individuals with Active and Sedentary Lifestyle

Abstract

Background: Activities of daily living consists of isometric & isotonic contraction. Isometric contraction is a static contraction that exerts pressure overload on the heart. Studies have been carried out demonstrating hemodynamic effects of isotonic exercises however limited studies are available on myocardial load with isometric exercises. Aims and Objectives: To study the myocardial load at 30% and 50% of maximal voluntary isometric contraction (MVIC) in individuals with active and sedentary lifestyle. Study design and setting: Observational cross-sectional study was carried out in a tertiary care hospital. Materials and Methods: 140 healthy subjects (70 each in active & sedentary group) were recruited for the study. Baseline demographics of both groups were comparable. Hemodynamic parameters were taken at rest. Subject performed 30% and 50% MVIC and hemodynamic parameters were recorded during and post contraction. Statistical Analysis: Paired t test was used to compare the myocardial load between 30% and 50% MVIC in both groups. Repeated measures ANOVA was used to compare the myocardial load between active & sedentary groups at 30% and 50% MVIC. Result: There was a statistically significant difference in heart rate, systolic blood pressure &rate pressure product between 30% and 50% in active as well as sedentary groups. There was statistically no significant difference in heart rate, systolic blood pressure & rate pressure product between active & sedentary groups at 30% and 50% MVIC. Conclusion: The myocardial load during activities at submaximal intensities (<50%) is within the physiological limits and can be performed safely in individuals with active and sedentary lifestyle.