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The Effect of Short-term Aerobic Exercise and Resistance Training on Heart Rate Variability in Response to Graded Head-Up Tilt

LJ Nickie - 2012 - Abstract: To evaluate the effects of short term aerobic and resistance training on cardiac autonomic response during orthostatic stress in young men; cardiac autonomic neural activity was determined by Fast Fourier Transformation (FFT) spectrum a frequency ...

To evaluate the effects of short term aerobic and resistance training on cardiac autonomic response during orthostatic stress in young men; cardiac autonomic neural activity was determined by Fast Fourier Transformation (FFT) spectrum a frequency domain method used to analyze spectral power in RR intervals as well as changes in short term heart rate variability. Data were collected at the Howard University Exercise Physiology lab from 22 healthy male participants whose health status was assessed through medical history forms submitted by participants as well as blood work collected before the study. The mean age of participants was 21.5+/-1.6 years. Subjects were separated into three groups--Untreated Benchmark Control Group (N= 5), Aerobic Group (N= 7) and Resistance Training Group (N= 6).

Each participant performed 5 minutes of paced breathing and 5 minutes of spontaneous breathing both before and after the exercise treatments. The aerobic exercise treatment consisted of 11 consecutive days of 30 minutes of running on a treadmill at a moderate work intensity level. Moderate work intensity is defined in this study as an exercise level in which the participants can carry on a conversation and exercise at the same time. The resistance exercise treatment lasted 10 minutes and consisted of bicep curls, bench press, arm curl, leg curl, leg extension, arm extension and abdominal curl performed at70% one RM/3 sets/@10 repetitions/set. The control group was also subjected to 5 minutes paced breathing and 5 minutes spontaneous breathing. Heart Rate Variability (HRV) data was then collected using an 800 head-up tilt orthostatic stress test pre and post on all participants across all groups. The RR intervals were evaluated through ECG and spectral amplitudes: Low-Frequency power (LF) defined as 0.04-0.15 Hz, High- Frequency power (HF) defined as 0.4-.15 Hz and LF/HF ratio defined as the Balance between sympathetic and parasympathetic activities. RSSMD is used in this study as an indicator of short term changes in HRV. All HRV proxies--LF, HF, LF/HF and RSSMD data were collected and evaluated using the Kruskal-Wallis non-parametric analysis of variance (ANOVA) tests.

During head up tilt, paced breathing, and spontaneous breathing after aerobic exercise training it was found that there were no significant increases in LF, HF, and LF/HF ratio (probability (p) ≤ 0.05). In contrast, the resistance exercise group exhibited increases in LF, HF, and LF/HF ratio (p ≤ 0.05) when subjected to both paced breathing and spontaneous breathing controls. The findings indicate an increase in sympathetic and parasympathetic activity as well as sympathovagal balance of the autonomic nervous system (ANS) for the resistance exercise participants. RMSSD was significant across both groups and all treatments (p ≤0.05) except for the spontaneous breathing treatment in the resistance group. Statistically significant increases in RMSSD across both groups indicate increases in the short term HRV through a higher degree of autonomic control of the heart via vagus nerve-mediation measures.

The findings of this study suggest that that 11days of aerobic and resistance exercise respectively have significant impacts on HRV when measured in the time domain. Resistance exercise particularly has a significant impact on all measures of HRV in both the time and frequency domain through increases in parasympathetic activity. This study allowed for the measurement of the effects each exercise treatment on HRV without confounds of exercise adaptation observed in long-term exercise training. These findings suggest that resistance exercise in the short-term has a much greater effect on HRV when compared to short term aerobic exercise training.