Heart Autonomic Control During Static Submaximal Contractions: Influence of Task Features

Background: Isometric exercise is important to cardiac rehabilitation, but understanding how different tasks can interfere with the Heart Rate Variability (HRV) still needs some clarification. Objective: To compare the Autonomic Nervous System (ANS) behavior during submaximal isometric tasks involving different muscle groups. Methods: Six healthy males ([Formula: see text] years old) performed two submaximal isometric tasks (30%) of knee extension and handgrip, sustained for 3[Formula: see text]min each, using visual feedback to maintain force levels. Successive RR intervals were recorded along the task, as well as for 5[Formula: see text]min before the task. Linear and nonlinear methods were used to obtain HRV parameters from successive RR intervals. Student [Formula: see text] test was used to compare the data with significant level set as [Formula: see text]. Results: Time domain parameters as well as the nonlinear parameters were significantly higher during the handgrip task. Conclusions: Submaximal isometric handgrip task is associated with a lower vagal withdrawal, when compared to submaximal isometric knee extension, suggesting that handgrip task promotes greater cardioprotection during exercise, while the isometric knee extension task could induce better adaptations to training.