Is Heart Rate Variablity a Suitable method For Monitoring The Effect Of A Training Session In Synchronized Swimming?

PURPOSE: To determine whether heart rate variability (HRV) is a suitable method for monitoring the effect of a training session (TS) in elite synchronized swimmers
METHODS: We recorded resting HRV (Rest) in 12 elite swimmers (mean age: 21.5±3.5 yrs) for 3 days over one week, interspersed by 48 h, prior to the 2015 World Swimming Championships. During the last TS, we continuously monitored heart rate (HR) and obtained salivary cortisol (SC) samples before and after the session. We measured capillary blood lactate (Lapeak) 2, 4, and 8 min after the TS and monitored recovery HRV (Rec), which was averaged for the following 5-min periods after the TS: Rec20-25, Rec25-30and Rec30-35. We assessed rate of perceived exertion (RPE) and tested the association between Lapeak, SC, and RPE and the relative changes (Δ%) of the natural logarithm (Ln) of the HRV-derived indices [standard deviations of the distance of rate to rate (SD1and SD2), the root mean square successive difference of intervals (RMSSD), and the high- and low-frequency domain parameters (HF and LF, respectively)]. We calculated the individual coefficient of variation (CV) of LnRMSSD for each recovery period.
RESULTS: LnLF (ms2) was lower in Rec25-30 (5.72±1.05) than in Rec20-25 and Rec30-35(6.68±0.97, 6.26±1.29; P<0.05). On average, CV=10.7%. Lapeakwas correlated positively with Δ%LnRMSSD, Δ%LnLF, Δ%LnSD1, and Δ%SC.
CONCLUSIONS: Isolated HRV data from synchronized swimmers may less accurate than other physiological markers for assessing the effect of TSs as a result of exercise bouts performed in apnea.