1. HUMAN PERFORMANCE LABORATORY
Time course for stabilization of heart rate variability among athletes and non-athletes during supine rest
 Andrew A. Flatt, M.Sc., Henry N. Williford, Ph.D., FACSM., Michael R. Esco, Ph.D., FACSM
Human Performance Laboratory, Auburn University Montgomery, Montgomery, AL
HUMAN PERFORMANCE LABORATORY
Introduction
Conclusion
Results
Resting HRV is a potentially useful marker to consider for monitoring training status in athletes (2). Traditional HRV data collection methodology requires a 5-min recording period preceded by a 5-min stabilization period. However, some researchers have used less than 5-min while others have used greater than 5 min for stabilization prior to HRV assessment. Therefore, there remains a wide discrepancy within sports science literature as it relates to appropriate pre-HRV-recording methodology.
Within the sports science literature HF, LF and RMSSD are commonly used HRV parameters for monitoring training status in athletes (1). However more recently, lnRMSSD has been suggested as the preferable parameter for athletes (2,6). This is in part due to its stability and reproducibility compared to spectral measures (5,8) as well as its potential suitability for ultra-short (i.e., 60-sec) assessment (4).
Determining the time-course for HRV stabilization in athletes is of particular importance for sport scientists who wish to include HRV in their monitoring protocols (4). The lengthy process of traditional 5-min stabilization periods may limit HRV monitoring in the field due to time constraints and high compliance demands of athletes (7). Investigation into more practical methodology for HRV data acquisitions is required.
In EA, lnRMSSD ranged from / to /- 0.41, lnHF ranged from / to /- 0.20, and lnLF ranged from / to / For NA, lnRMSSD ranged from / to /- 0.42, lnHF ranged from / to /- 0.63, and lnLF ranged from / to / There was no effect for time among the HRV measures in either group (p > 0.05). The parameters were significantly different (p < 0.05) between EA versus NA at each time point for lnRMSSD, all time points except 4-9m for lnHF, and all time points except 4-9-min, 5-10-min, and 6-11-min for lnLF.
Established guidelines recommend that short-term HRV be recorded under physiological stable conditions (3). Traditional HRV recording procedures utilize a 5-min stabilization period preceding HRV analysis which may be too lengthy for implementation in the sports domain for routine athlete monitoring (4,7). This study aimed to determine the time course for stabilization of commonly used HRV parameters in athletes and healthy controls in 5-minute segments across 15-min.
The results demonstrated that lnRMSSD stabilizes within the first minute of ECG recording compared to lnHF and lnLF in EA and NA. lnRMSSD and lnHF appeared more stable than lnLF among both groups which is in agreement with previous work (5,8). Thus, lnRMSSD may be a preferable parameter for athlete monitoring when shorter recording procedures are desired. The current results lend support to shorter, more convenient HRV recording procedures by utilizing a shorter (e.g., 60 second) stabilization period prior to HRV recording for lnRMSSD assessment.
Abstract
Established guidelines recommend a 5 minute (-min) stabilization period prior to electrocardiograph (ECG) recordings for short-term heart rate variability (HRV) analysis. However, time constraints in the sports domain do not always allow for such lengthy procedures when daily HRV recordings are used for athlete monitoring. Shorter procedures for collecting HRV data are desirable and thus require investigation.
PURPOSE: The purpose of this study was to determine the time course of stabilization for several HRV indices over a 15-min supine ECG recording in collegiate endurance athletes (EA) and non-athletes (NA). It is likely that HRV stabilization in athletes may be achieved in less than 5-min, thus suggesting the suitability of a shorter stabilization period.
METHODS: 15-min ECG recordings were collected in the laboratory during supine resting conditions in 12 EA (6 male) and 12 NA (6 male). Log-transformed (ln), normalized high (lnHF) and low frequency (lnLF) spectral power and ln root mean square of successive R-R intervals (lnRMSSD) were assessed from each of the 15-min ECG segments in the following 5-min intervals: 0-5; 1-6; 2-7; 3-8; 4-9; 5-10; 6-11; 7-12; 8-13; 9-14; and min, respectively.
RESULTS: In EA, lnRMSSD ranged from / to /- 0.41, lnHF ranged from / to /- 0.20, and lnLF ranged from / to / For NA, lnRMSSD ranged from / to /- 0.42, lnHF ranged from / to /- 0.63, and lnLF ranged from / to / There was no effect for time among the HRV measures in either group (p > 0.05). The parameters were significantly different (p < 0.05) between EA versus NA at each time point for lnRMSSD, all time points except 4-9m for lnHF, and all time points except 4-9-min, 5-10-min, and 6-11-min for lnLF.
CONCLUSION: This study suggests that the assessment of short-term HRV in the supine position may likely be performed with shorter stabilization requirements than traditional recommendations in both EA and NA.
References
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Aim
The purpose of this study was to determine the time course for stabilization of lnRMSSD, lnHF and lnLF over a 15-min supine ECG recording in collegiate endurance athletes (EA) and non-athletes (NA).
Figure 1. EA lnRMSSD = Endurance Athletes log transformed Root Mean Square of Successiver R-R intervals, EA lnHF = Endurance Athletes log transformed High Frequency normalized units, EA lnLF = Endurance Athletes log transformed Low Frequency normalized units.
Methods
Subjects
Twenty-four male (n=12) and female subjects volunteered for this study. Twelve (n = 6 male) were EA from the University’s cross-country team and 12 (n = 6 male) were NA from the Kinesiology Department.
Experimental Design
For each subject, 15-min ECG recordings were collected in the laboratory during supine resting conditions closely after awakening from sleep. lnHF and lnLF spectral power and lnRMSSD were assessed from each of the 15-min ECG segments in the following 5-min intervals: 0-5; 1-6; 2-7; 3-8; 4-9; 5-10; 6-11; 7-12; 8-13; 9-14; and min, respectively.
Figure 2. NA lnRMSSD = Non-Athletes log transformed Root Mean Square of Successive R-R intervals, NA lnHF = Non-Athletes log transformed High Frequency normalized units, NA lnLF = Non-Athletes log transformed Low Frequency normalized units.