Cardiac Autonomic and Salivary Responses to a Repeated Training Bout in Elite Swimmers

The measurement of heart rate variability (HRV) is often considered a convenient non-invasive assessment tool for monitoring individual adaptation to training. Decreases and increases in vagal-derived indices of HRV have been suggested to indicate negative and positive adaptations, respectively, to endurance training regimens. However, much of the research in this area has involved recreational and well-trained athletes, with the small number of studies conducted in elite athletes revealing equivocal outcomes. For example, in elite athletes, studies have revealed both increases and decreases in HRV to be associated with negative adaptation. Additionally, signs of positive adaptation, such as increases in cardiorespiratory fitness, have been observed with atypical concomitant decreases in HRV. As such, practical ways by which HRV can be used to monitor training status in elites are yet to be established. This article addresses the current literature that has assessed changes in HRV in response to training loads and the likely positive and negative adaptations shown. We reveal limitations with respect to how the measurement of HRV has been interpreted to assess positive and negative adaptation to endurance training regimens and subsequent physical performance. We offer solutions to some of the methodological issues associated with using HRV as a day-to-day monitoring tool. These include the use of appropriate averaging techniques, and the use of specific HRV indices to overcome the issue of HRV saturation in elite athletes (i.e., reductions in HRV despite decreases in resting heart rate). Finally, we provide examples in Olympic and World Champion athletes showing how these indices can be practically applied to assess training status and readiness to perform in the period leading up to a pinnacle event. The paper reveals how longitudinal HRV monitoring in elites is required to understand their unique individual HRV fingerprint. For the first time, we demonstrate how increases and decreases in HRV relate to changes in fitness and freshness, respectively, in elite athletes.

This paper discusses the use of saliva analysis as a tool for monitoring steroid, peptide, and immune markers of sports training. Salivary gland physiology, regarding the regulation and stimulation of saliva secretion, as well as methodological issues including saliva collection, storage and analysis are addressed in this paper. The effects of exercise on saliva composition are then considered. Exercise elicits changes in salivary levels of steroid hormones, immunoglobulins, antimicrobial proteins and enzymes. Cortisol, testosterone and dehydroepiandrosterone can be assessed in saliva, providing a non-invasive option to assess the catabolic and anabolic effects of exercise. Validation studies using blood and salivary measures of steroid hormones are addressed in this paper. Effects of acute exercise and training on salivary immunoglobulins (SIgA, SIgM, SIgG) and salivary antimicrobial proteins, including α-amylase, lysozyme and lactoferrin, are also discussed. Analysis of cortisol and testosterone in saliva may help detect the onset of non-functional overreaching and subsequently may help to prevent the development of overtraining syndrome. Assessment of salivary immunoglobulins and antimicrobial proteins has been shown to successfully represent the effects of exercise on mucosal immunity. Increases in SIgA and antimicrobial proteins concentration and/or secretion rate are associated with acute exercise whereas conversely, decreases have been reported in athletes over a training season leaving the athlete susceptible for upper respiratory tract infections. The measurement of physiological biomarkers in whole saliva can provide a significant tool for assessing the immunological and endocrinological status associated with exercise and training. Copyright © 2011 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Measures of an athlete's heart rate variability (HRV) have shown potential to be of use in the prescription of training. However, little data exists on elite athletes who are regularly exposed to high training loads. This case study monitored daily HRV in two elite triathletes (one male: 22 year, VO2max 72.5 ml kg min(-1); one female: 20 year, VO2max 68.2 ml kg min(-1)) training 23 ± 2 h per week, over a 77-day period. During this period, one athlete performed poorly in a key triathlon event, was diagnosed as non-functionally over-reached (NFOR) and subsequently reactivated the dormant virus herpes zoster (shingles). The 7-day rolling average of the log-transformed square root of the mean sum of the squared differences between R-R intervals (Ln rMSSD), declined towards the day of triathlon event (slope = -0.17 ms/week; r2 = -0.88) in the NFOR athlete, remaining stable in the control (slope = 0.01 ms/week; r2 = 0.12). Furthermore, in the NFOR athlete, coefficient of variation of HRV (CV of Ln rMSSD 7-day rolling average) revealed large linear reductions towards NFOR (i.e., linear regression of HRV variables versus day number towards NFOR: -0.65%/week and r2 = -0.48), while these variables remained stable for the control athlete (slope = 0.04%/week). These data suggest that trends in both absolute HRV values and day-to-day variations may be useful measurements indicative of the progression towards mal-adaptation or non-functional over-reaching.