Cardiac autonomic recovery after strength exercise in lower and upper limbs

Introduction Strength exercises influence the cardiovascular system by promoting autonomic adjustments induced by the increased metabolic demand and consequent increase in local blood flow. However, it is unclear whether there are differences between upper and lower limbs. We aimedto evaluate recovery of cardiac autonomic modulation afterstrengthexercise in upper and lower limbs. Methods We analysed 29 healthy male subjects physically active but not professional athletes aged between 20 and 35 years old. We analysed heart rate variability (HRV) in the time and frequency domain 0-10 minutes before exercise (T1), 0-10 minutes after exercise (T2), 10-20 minutes after exercise (T3) and 20-30 minutes after exercise (T4). Results Regarding the time domain we observed that the SDNN, pNN50 and RMSSD were reduced (P < 0.0001) in T2, T3, T4 in relation to T1 with no difference between upper and lower limbs. In the frequency domain analysis, we observed stronger significancefor the increased values of LF (nu) (P = 0.0008) and LF/HF ratio (P = 0.0008) and for reduction in HF (nu) (P = 0.0008) in the lower limbs compared to upper limbs (LF (nu) - P = 0.0015, LF/HF ratio - P = 0.0028 and HF (nu) - P = 0.0028). Conclusion Strength exercise acutely induced more pronounced cardiac autonomic responses in lower limbs compared to upper limbs.