RELIABILITY OF HEART RATE VARIABILITY DURING DYNAMIC HANDGRIP EXERCISE

Abstract

This study examined test-retest reliability of heart rate variability (HRV) during low (H20:20%MVC) and high (H60: 60%MVC) intensity dynamic handgrip exercise. 6 women and 3 men (age:22 ± 2yrs) participated in three tests with no more than two weeks between sessions. During each session, MVC was measured and handgrip exercise (0.50 hz) performed using a Biodex handgrip dynamometer. Visits land 3 (V1 and V3) consisted of 5 minutes of both H20 and H60 exercise, each preceded by 5 min spontaneous breathing (SB) in the supine position (SB1 and SB2, respectively). Visit 2 (V2) involved 5 min of SB1 and 5 minutes of H60 exercise. ECG (Biopac MP100) were continuously collected during each session. Data were analyzed in 2.2 min segments using MATLAB and Acqknowledge (3.0) software to obtain mean R-R interval, standard deviation (SDNN), low frequency (LF: 0–0.15 hz) and high frequency (HF:0.15–0.40hz) power, and normalized frequency units (power/sum of LF and HF). A repeated measure ANOVA with Tukey's post hoc analysis was used to test for significance across day and condition. Reliability was tested using Hoyt's reliability analysis. Mean R-R (V3: SB1:943.3 ± 129.2ms, H20: 883.8 ± 140.7ms, SB2:943.0 ± 147.9ms, H60:756.5 ± 112.6ms) and HFnu (V3:SB1:44.7 ± 24.8%, H20:47.6 ± 26.0%, SB2:29.8 ± 17.9%, H60:29.1 ± 19.7%) decreased and LFnu (V3:SB1:55.3 ± 24.8%, H20:52.4 ± 26.0%, SB2:70.2 ± 17.9%, H60:70.9 ± 19.7%) increased in an intensity dependent manner during exercise (p < 0.05). SDNN decreased during exercise (V3: SB1:56.2 ± 30.2ms, H20:40.7 ± 16.0ms, SB2:92.6 ± 33.6ms, H60:39.6 ± 17.4ms; p < 0.05 from SB), but was not intensity dependent. The reliability coefficients for R-R and HRV are in the table. These data indicate time and frequency domain during dynamic exercise are reliable over a one month period.Table