Variation in Response and Recovery to Training Intensity in Highly Trained Rowers

Background: In endurance sports, where training loads are high, effective programming of day-to-day training is crucial to achieve sufficient training stimuli and adequate recovery for optimal adaptation. The time required for recovery to a pre-exercise state following a single exercise stimulus is influenced by exercise intensity, although studies to date investigating this influence implement passive recovery periods. This does not reflect a real-world setting, where high training frequencies often require subsequent training to be performed prior to complete recovery. Furthermore, no study has investigated the influence of energetic profile on recovery time-course, which may prove valuable in individualising training programming. Aims: 1) To quantify the acute post-exercise deviation and time-course for recovery to baseline following different high-intensity interval training sessions throughout a non- passive recovery period. 2) To investigate the influence of energetic profile on the acute deviation and time-course for recovery to baseline. Methods: Ten male and three female highly trained rowers (mean ±SD age: 20.2 ±3.7 yr; body mass: 83.4 ±9.4 kg; VO₂peak: 4.93 ±0.71 L⋅min-1) completed preliminary testing to determine energetic contribution to a 6 min maximal rowing test. On separate days, participants completed three interval training (IT) sessions on the rowing ergometer: 5 x 3.5 min, 4 min rest periods (VO₂); 10 x 30 s, 5 min rest periods (Glycolytic); and 5 x 10 min, 4 min rest periods (Threshold). Intervals were requested to be performed at the highest possible maintainable pace. Blood lactate and salivary cortisol were measured pre, 3 and 30 min post-exercise respectively. Resting heart rate (HR) variability (HRV), post-submaximal exercise HRV (HRVex), submaximal HR (HRex), HR recovery (HRR), modified Wingate peak power and mean power, and subjective recovery (REC-Q) were measured pre and 1, 10, 24, 34, 48, 58, and 72 h post-exercise. Study One involved the comparison of mean acute post-exercise deviation and time-course for recovery to baseline data between the three IT sessions. Study Two retrospectively selected four male and two female participants from Study One for matched pair comparison. Pairs were matched for performance capacity (<1% difference in 6 min mean test power or 2000 m test time) with differing energetic profiles (>6.8% difference in aerobic energy system contribution to the 6 min rowing test). Results: Study One found either trivial or unclear differences in the acute deviation from baseline of blood lactate, salivary cortisol, HRV, HRVex, HRex, HRR, REC-Q, modified Wingate mean and peak power between IT sessions. HRVex had the longest time-course for baseline return: 37.8 ±14.2 h (mean ± CL) post-Threshold, 20.2 ±11.0 post-Glycolytic, and 20.6 ±15.2 h post-VO₂ IT. Partial correlations revealed participants with greater aerobic energetic contributions to have shorter recovery time-courses for HRR following Threshold IT (r = -0.52 ±0.51), but longer recovery time-courses for HRex following Threshold IT (r = 0.53 ±0.51) and HRVex following Glycolytic IT (r = 0.36 ±0.47) in the analysis of all thirteen participants. In Study Two matched pair comparison revealed participants with greater anaerobic energetic contributions (AnT) had a 64.1 ±103.4% (mean ±SD) greater blood lactate response across IT sessions than participants with greater aerobic contributions (AeR). AeR illustrated larger acute HRV (17.7 ±216.2%), HRVex (40.1 ±68.7%), HRR (76.4 ±168.5%), cortisol (229.2 ±479%), and HRex (57.0 ±113.9%) responses across IT sessions. Larger acute mean power reduction (107.6 ±100.8%) in AnT across IT sessions. Longer HRVex (18.0 ±35.9 h) and HRex (10.5 ±18.0 h) recovery-time courses in AeR, with no consistent difference in recovery-time course for HRV, HRR, mean or peak power between AeR and AnT. Conclusion: Acute deviations from baseline were similar following Threshold, Glycolytic, and VO₂ IT across all recovery variables measured in highly-trained male and female rowers. However, following resumption of training, return to a pre-exercise state is prolonged following Threshold compared to Glycolytic and VO₂ IT. Suggesting the existence of a durational effect on time to recover following exercise performed at HR intensities reflective of ≥VT₂. In addition, athletes presenting greater aerobic contributions demonstrate higher rates of parasympathetic recovery in comparison to athletes presenting greater anaerobic energetic contributions, however this did not correspond to differences in recovery time-course. These findings indicate energetic contribution to have limited practical influence on individualising the programming of high-intensity interval sessions, with regards to the time-course of recovery between acute sessions. However, the influence of individualising training programming with regard to energetic profile on the long-term adaptive response is unknown, and thus warrants further research