Training adaptation and heart rate variability in elite endurance athletes: opening the door to effective monitoring
Key Findings
HRV (vagal-derived indices) is a convenient non-invasive tool for monitoring individual adaptation to training. The usual reading — decreases = negative adaptation, increases = positive adaptation — comes mostly from recreational and well-trained athletes.
In elite athletes the picture is equivocal: studies have found both increases and decreases in HRV associated with negative adaptation, and positive adaptation (increased cardiorespiratory fitness) has been observed with concomitant decreases in HRV.
HRV saturation: in elites, HRV can fall despite a falling resting heart rate — a high-vagal-tone artefact, not fatigue. Specific HRV indices are needed to see through it.
Averaging matters: single-day values are noisy; the review recommends appropriate averaging techniques rather than day-to-day reading. Full text (not checked against the abstract): 7-day rolling average of Ln rMSSD, with its coefficient of variation as a second signal.
Individual fingerprint: longitudinal monitoring in elites is required to understand each athlete's unique HRV pattern; cross-athlete comparison is not meaningful.
Case data (Olympic and World Champion athletes): for the first time the authors show increases in HRV relating to changes in fitness and decreases relating to freshness in the lead-up to a pinnacle event — a falling HRV before a peak can be the taper working, not fatigue.
Practical Application
Narrative review + elite case data (Plews 2013): in elite endurance athletes both rises and falls in HRV have been linked to negative adaptation, fitness gains have come with falling HRV, and HRV can drop simply because resting HR drops (saturation); the authors' own Olympic/World-Champion data show HRV increases tracking fitness and decreases tracking freshness. Read HRV as a rolling trend, against resting HR and the training phase, per athlete — not as a daily go/no-go number.
Use an averaged index (full text: 7-day rolling Ln rMSSD), not a single morning value, and log it long enough to learn the athlete's own pattern before interpreting anything.
When Ln rMSSD falls together with resting HR in a fit athlete, consider saturation before fatigue; when it falls during a taper, consider freshness before fatigue.
Combine with resting HR, subjective wellness and the training context — the review offers HRV as a door to monitoring, not a stand-alone readiness score.
Limitations
Narrative review; the elite evidence is a small number of studies plus the authors' own case data — equivocal by the authors' own account
Individual variability in HRV baseline enormous; comparison across athletes not meaningful — within-individual only
HRV affected by hydration, alcohol, late-night food, temperature, illness → signal can be confounded
Not a single readiness index — requires subjective + resting HR + training-load context
Wearable HRV measurement quality varies (see REF-364)
How this entry was checked and changed
Why this level
regraded 2026-09-27 from A: narrative review from the leading group
Content correction 2026-09-27
"Increasing trend = adaptation; sustained decline = accumulating fatigue" -> in elites both increases and decreases have been linked to negative adaptation, fitness gains occur with falling HRV (saturation), and the authors' case data tie increases to fitness and decreases to freshness.
Decision rules ("> 1 SD for 2+ days → reduce, 4+ days → extended recovery"), "4-6 week baseline", "slow-wave sleep strongly correlated", morning-measurement protocol -> not in this paper; deleted or marked not from this paper.
7-day rolling Ln rMSSD / CV -> kept, marked as full text not checked against the abstract.
Cross-reference descriptions checked against the cited entries' current content; wrong years, wrong entries and claims the cited entry does not make were corrected.
Resync 2026-09-28: Two places labelled REF-362 'Bellenger 2016' (an unverified companion review) -> Javaloyes 2019, the entry's verified RCT.