Monitoring training in women's volleyball: Supine or seated heart rate variability?

Highlights

• Submaximal exercising heart rate varied inversely with seated LnRMSSD_M.

• Seated LnRMSSD_CV was the most sensitive HRV metric to changes in training load.

• Less fluctuation in seated LnRMSSD was often associated with positive adaptations.

• Seated HRV seems preferable to supine recordings for monitoring volleyball players.

Abstract

We aimed to examine changes in resting heart rate variability, submaximal exercising heart rate (HRex), countermovement-jump height (CMJ), perceptual wellbeing, and internal load throughout preparatory training in elite women's volleyball players. We also aimed to determine which HRV measurement position (supine vs. seated) provided greater associations with the various markers of training adaptation. Thirteen players (age = 25.8 ± 3.0 years, height = 178.1 ± 6.7 cm, weight = 69.7 ± 7.6 kg) were monitored throughout four successive training camps preceding the Asia Cup. Daily measures of the root-mean square of successive differences were used to calculate the mean (LnRMSSD_M) and coefficient of variation (LnRMSSD_CV) for each camp. Averages were also determined for Hooper's Index and session ratings of perceived exertion (sRPE). HRex and CMJ were tested at the start of each camp. RESULTS: Seated LnRMSSD_CV, HRex, CMJ, and sRPE increased at camp 3 (p < 0.05), then reverted to values similar to camp 2. Changes in seated LnRMSSD_M were associated with changes in HRex (r = -0.68 to -0.71, p < 0.05). Occasional associations (p < 0.05) were observed between LnRMSSD_CV and Hooper's Index (r = 0.59) and CMJ (r = -0.57), and changes in HRex (r = 0.69) and HRR (r = -0.62). CONCLUSIONS: A reduced cardiorespiratory response to a standardized submaximal workload was associated with increased seated LnRMSSD_M. Higher seated LnRMSSD_CV was observed in response to increased sRPE and was often associated with decrements in various status markers. Seated LnRMSSD provided more associations with indicators of training adaptation than supine measures.

Introduction

Volleyball is an intermittent sport that involves short bouts of high intensity movements such as spiking, blocking, serving, and passing [1]. The physical demands of volleyball simultaneously challenge cardiovascular and neuromuscular systems. Therefore, quickness, agility, jumping ability, as well as aerobic and anaerobic power are important determinants of performance [1,2]. Volleyball players are typically exposed to high training loads preceding competitions due to an increased frequency of training sessions [3]. Periods of concentrated loads can disturb the balance between training and recovery, and may consequently increase the occurrence of overreached states among players. Therefore, further investigation into player-monitoring strategies is needed so that practitioners can more effectively evaluate individual adaptations, guide training, and optimize performance [4].

Effective player-monitoring protocols include workload quantification and tracking of variables related to cardiovascular, neuromuscular, and subjective status to comprehensively inform on training adaptations [1,5]. Accordingly, heart rate (HR) responses [6], jumping performance [7], and self-reported subjective measures [7,8] reflect independent markers of status that can be implemented in applied settings. Exercising heart rate (HRex), and HR recovery (HRR) from a standardized submaximal running test have shown promise for monitoring athletes’ aerobic fitness status [4,9]. The countermovement jump (CMJ) is a marker of lower-body power that is specific to volleyball performance and sensitive to training-related changes [7]. In addition, subjective coping responses are assessed via wellness questionnaires such as Hooper's Index [10] and are sensitive to fluctuations in training load [8]. Finally, session rating of perceived exertion (sRPE) provides subjective quantification of internal load in volleyball players [11]. To our knowledge, no previous study has examined how these variables concurrently evolve throughout preparatory training in women's volleyball players.

Heart rate variability (HRV) is an objective physiological marker used to assess autonomic nervous system status in response to physical training [4,[12], [13], [14], [15]]. The preferred vagal-related HRV parameter for monitoring athletes is the natural logarithm of the root mean square of successive R-R interval differences (LnRMSSD) [4]. Isolated (i.e., single-time point) recordings are less sensitive to training responses than more frequent monitoring, necessitating a minimum of three LnRMSSD recordings to sufficiently quantify a weekly mean (LnRMSSD_M) and its daily variation (i.e., coefficient of variation, LnRMSSD_CV) [6,16]. Weekly LnRMSSD values are sensitive to training loads [16], [17], [18], [19] and are associated with changes in exercise performance [12,16]. For example, increased or stable LnRMSSD_M and reductions in LnRMSSD_CV have been associated with improvements in aerobic fitness [12,[18], [19], [20], [21]]. Contrastingly, reductions in LnRMSSD_M and increments in LnRMSSD_CV have been observed in athletes showing signs of fatigue or responding unfavorably to training [12,13,22]. Whether weekly LnRMSSD parameters are associated with markers of fitness, performance, or subjective training responses in women's volleyball players is currently unknown.

LnRMSSD varies as a function of body position during recordings (e.g., seated, supine), which may affect its sensitivity to training load, performance, and fatigue [16,23]. Lying supine facilitates an undisturbed resting condition, whereas an upright position provokes autonomic modulation of HR and blood pressure to overcome gravitational pooling of blood in the lower extremity [24]. Monitoring HRV from measures obtained in multiple positions increases compliance demands of athletes. Therefore, determining which HRV measurement position provides the greatest sensitivity to training responses is needed to guide efficient monitoring protocols.

Few investigations have examined the utility of HRV in volleyball players. Available studies have reported equivocal findings [25,26] and have methodological limitations related to reliance on isolated measures, or supine-only recordings [6,25]. Therefore, we aimed to examine changes in cardiac-autonomic, cardiorespiratory, neuromuscular, and perceptual markers throughout preparatory training camps in elite women's volleyball players. A secondary aim was to determine which LnRMSSD measurement position (i.e., supine versus seated) provided greater associations with the various markers of training adaptation.