Recovery

The autonomic nervous system (ANS) regulates involuntary bodily functions including heart rate, blood pressure, digestion, and respiration. It is traditionally divided into…

Baroreflex sensitivity (BRS) quantifies the magnitude of the heart rate response to acute changes in arterial blood pressure, expressed as milliseconds of RR-interval change per…

Delayed-onset muscle soreness (DOMS) is the diffuse muscular pain, stiffness, and tenderness that develops 24–72 hours after unaccustomed or eccentric-heavy exercise, peaking…

Heart rate variability is the beat-to-beat fluctuation in time between successive heartbeats, measured in milliseconds. Within a healthy sinus rhythm, higher values typically…

Frequency-domain HRV analysis decomposes the beat-to-beat interval spectrum into bands: high frequency (HF, 0.15–0.4 Hz) primarily reflects respiratory sinus arrhythmia driven by…

Overtraining syndrome (OTS) sits on a continuum with functional overreaching (FOR) and non-functional overreaching (NFOR), per ECSS/ACSM consensus. It is a maladaptive state in…

Parasympathetic activation refers to engagement of the rest-and-digest branch of the autonomic nervous system, primarily mediated by the vagus nerve to thoracic and…

pNN50 is a time-domain HRV index defined as the percentage of consecutive normal-to-normal (NN) R–R interval pairs differing by more than 50 ms. It equals NN50 — the count of…

A readiness score is a vendor-defined daily index, popularized by devices like Oura and Garmin (whose analogous metric is branded Training Readiness or Body Battery), that aims…

Recovery score is a generic category for vendor-defined composite metrics that estimate how well the body has recuperated from prior strain. Branding differs by device: Whoop…

RMSSD (Root Mean Square of Successive Differences) is a time-domain HRV metric defined as the square root of the mean of the squared successive differences between adjacent NN…

Rate of perceived exertion (RPE) is a subjective scale used to quantify how hard physical exercise feels, most commonly on the 6–20 Borg scale or the 0–10 modified scale. It…

SDNN (Standard Deviation of NN intervals) is a time-domain HRV measure capturing the overall variability of normal heartbeats. Per HRV Task Force standards, SDNN is primarily…

Sympathetic dominance describes a chronic shift in autonomic balance toward sustained sympathetic nervous system activation relative to parasympathetic tone, typically reflected…

Vagal tone describes the baseline activity of the vagus nerve, the primary parasympathetic pathway connecting the brainstem to organs including the heart, lungs, and gut. Higher…