How well is your athlete coping with the current training load? How long can an individual athlete cope with intensified training before he/she becomes non-functional? Here, Simon Wegerif will demonstrate how heart rate variability (HRV) can reliably indicate when the planned training can safely continue versus when load should be modified.
Many coached endurance training programs are periodized, meaning they contain blocks of intensified training where volumes and/or intensities are increased above baseline level, followed by a deloading phase or taper towards an event or competition.
It’s expected that performance will temporarily decrease during the intensified period and then bounce back or super-compensate during the taper to a new, higher level.
The exact combination of loads, intensities, and volumes to stress the body sufficiently to stimulate adaptation depends on the individual athlete and their state of both training and general life stress at that point in time. Too little stimulus and the athlete’s performance will not improve, whereas overdo the stimulus and they can get cooked or sick, with no improvement either.
Judging the right balance is an art for the coach who knows their athletes, but can science help us detect when overreaching may be non-functional?
Research to the Rescue
Vuelta a España Study
A study conducted on riders in the Vuelta a España demonstrates how dramatic the impact of continued punishment is day after day on the riders’ autonomic nervous system. The below was assessed using heart rate variability (HRV).
During the early stages of the tour, the riders’ HRV was an average of 55ms. Then, during the demanding second week of the tour, which consisted of four mountain stages and two long flat stages, several riders’ nervous systems became sympathetic – fight or flight – dominated.
At the end of the tour, the lowest recorded number (around 17 ms) was from a domestique team member. This was very low, and, in the words of one of the study’s authors, comparable to a ‘heart attack patient.’ The protected team leader, however, achieved two stage victories during this period.
Recreational Runners Study
In this study, a deliberate overload period was placed on recreational runners.
The athletes were divided into two groups for analysis based on their maximal performance at the end of the overload stage.
- Acute fatigue (AF): Seven athletes who maintained or improved performance.
- Functionally overreached (FOR): Eight athletes with decreased performance.
In terms of HRV, there was relatively little difference at the end of the overload period, but there were two useful observations made:
- HRV taken in the standing position produced much more consistent results compared to when taken lying down supine.
- The trajectory taken by HRV during recovery was dramatically different between the runners classed as AF versus those classed as FOR.
This second point is important because higher HRV during taper (RCV, compared to baseline BSL) has been associated with improved performance – meaning, the training has worked. The performance of the FOR group dropped slightly at the end of the overload and improved only slightly at the end of recovery, compared to the AF group that improved continuously.
It’s also worth noting that there was a significant difference in physical subjective scores between the two groups at the end of the overload period.
Practical Takeaways
Based on the above studies, there are three practical takeaways:
- HRV can be a useful and practical way to assess the impact of chronic training loads on an athlete, especially in the context of total load (i.e. non-training stress).
- HRV baseline decreasing during intensified training will depend on the degree of overload. It will also depend on the characteristics of the individual athlete, including training status, attention to recovery, and total load.
- If an athlete’s HRV baseline increases following a taper, it shows that good adaptations have taken place. This is a good sign for increased performance.
To effectively detect overreaching that may become non-functional (for example, no performance gain even after recovery), coaches and athletes should also record wellness and fatigue metrics, especially during periods of significantly increased loads when metrics like TSB and the acute chronic training load ratio get worse.
References:
N. Bourdillon et al. / Journal of Science and Medicine in Sport 21 (2018) 941–949
Relation between physical exertion and heart rate variability characteristics in professional cyclists during the Tour of Spain
C P Earnest, R Jurca, T S Church, J L Chicharro, J Hoyos and A Lucia
Br. J. Sports Med. 2004;38;568-575
