Individual Adaptation to Endurance Training Guided by Heart Rate Variability

Ida Heikura (2015). Individual adaptation to endurance training guided by heart rate variability. Department of Biology of Physical Activity, University of Jyväskylä, Master’s Thesis in Exercise Physiology. 65 pp. Heart rate variability (HRV) reflects the function of the cardiac autonomic system. Therefore, planning daily endurance training based on HRV has been suggested to be a potential training method compared to preprogrammed training. The purpose of this study was to examine the effects of an individualized training program based on 7-day rolling averaged HRV on endurance training adaptation. Methods. A total of 40 recreational endurance runners, 20 women (age 34.0 ± 7.8 yr, VO2max 48.6 ± 4.4 ml/kg/min) and 20 men (age 35.4 ± 6.6 yr, VO2max 55.5 ± 5.3 ml/kg/min) volunteered for the study. For the final analysis, 31 subjects were included. All subjects trained similarly during the first 4-week training period, after which they were matched for age, sex, endurance performance and HRV into two training groups (HRV and TRAD) for the eight-week long second training period. HRV group trained according to a 7-day rolling averaged morning RMSSD (RMSSDrollavg), whereas TRAD trained based on a predetermined training program. HRV trained at high intensity on days when the RMSSDrollavg was within the individually determined smallest worthwhile change (SWC) and when the RMSSD was outside this area subjects did low intensity training. TRAD did 50 % of the training at high intensity during the second period. Individual training frequency was kept unchanged throughout the study in all groups. Endurance performance was measured with a maximal incremental running test on a treadmill and a field 3000 m running test. HRV group measured real-time morning RMSSD with Omegawave. Nightly HRV was measured with Garmin HR monitor and analyzed with Firstbeat SPORTS software. Results. The velocity in the 3000 m run improved in HRV (2.1 %, p = 0.004) but not in TRAD. In contrast, VO2max increased in both HRV (3.7 %, p = 0.027) and TRAD (5.0 %, p = 0.002). Maximum velocity (2.6 %, p = 0.005; 2.1 %, p < 0.001) and velocities at LT2 (2.6 %, p = 0.025; 1.9 %, p = 0.004) and LT1 (2.8 %, p = 0.028) on a treadmill increased significantly in HRV and all but VLT1 in TRAD, respectively. RMSSDday (-25.3 %) and RMSSDrollavg (-8.3 %) decreased from pre to post. The CV for the mean RMSSDday was 14.5 %, whereas for the RMSSDrollavg it was 6.7 %. Conclusion. The change in the 3000m run velocity improved in HRV but not in TRAD even though HRV did less HIT. RMSSDrollavg provides a more reliable method to assess the response to training compared to RMSSDday which has more day-to-day variability. Future studies should further investigate HRV guided training and aim to find a reliable protocol for field practice. Based on the results of the current study, the use of HRV in planning daily endurance training to optimize training adaptation is highly recommended.