Capsaicin and Its Effect on Exercise Performance, Fatigue and Inflammation after Exercise

Abstract

Capsaicin (CAP) activates the transient receptor potential vanilloid 1 (TRPV₁) channel on sensory neurons, improving ATP production, vascular function, fatigue resistance, and thus exercise performance. However, the underlying mechanisms of CAP-induced ergogenic effects and fatigue-resistance, remain elusive. To evaluate the potential anti-fatigue effects of CAP, 10 young healthy males performed constant-load cycling exercise time to exhaustion (TTE) trials (85% maximal work rate) after ingestion of placebo (PL; fiber) or CAP capsules in a blinded, counterbalanced, crossover design, while cardiorespiratory responses were monitored. Fatigue was assessed with the interpolated twitch technique, pre-post exercise, during isometric maximal voluntary contractions (MVC). No significant differences (p > 0.05) were detected in cardiorespiratory responses and self-reported fatigue (RPE scale) during the time trial or in TTE (375 ± 26 and 327 ± 36 s, respectively). CAP attenuated the reduction in potentiated twitch (PL: -52 ± 6 vs. CAP: -42 ± 11%, p = 0.037), and tended to attenuate the decline in maximal relaxation rate (PL: -47 ± 33 vs. CAP: -29 ± 68%, p = 0.057), but not maximal rate of force development, MVC, or voluntary muscle activation. Thus, CAP might attenuate neuromuscular fatigue through alterations in afferent signaling or neuromuscular relaxation kinetics, perhaps mediated via the sarco-endoplasmic reticulum Ca²⁺ ATPase (SERCA) pumps, thereby increasing the rate of Ca²⁺ reuptake and relaxation.

Keywords: afferent; cardiac output; metabolism; motoneuron; perfusion; skeletal muscle; ventilation.

Figure 1

Experimental design of the study. After familiarization, participants reported to the lab on the first day for an incremental test. One week later, they were allocated in one of the two conditions, placebo (PL) or capsaicin (CAP). The neuromuscular assessment then started with 6 maximal voluntary contractions (MVC) using the interpolated twitch technique, which was repeated immediately following the time to exhaustion trial (85% W_peak of the incremental test). After one week of washout, the participants proceeded with the same assessments with the other condition.

Figure 2

Sample Absorbance signal from High-Performance Liquid Chromatography (HPLC) analysis of Capsaicin supplement used for the quantification of the Capsaicinoids, Capsaicin, and Dihydrocapsaicin.

Figure 3

Time to exhaustion (TTE) and its correlation with the resting potentiated twitch (QT_w,pot) after exercise (n = 10). (A) Time to exhaustion in individual valued after CAP or PL ingestion; (B) Time to exhaustion correlated with the QT_w,pot showed a significant positive correlation in both PL (r = 0.7, p = 0.04) and CAP (r = 0.7, p = 0.04). Values are presented as individual data and Mean ± SEM.

Figure 4

Neuromuscular Function Parameters expressed as the exercise-induced relative change after the time to exhaustion (TTE) in young active males (n = 10). (A) Maximal voluntary contraction. (B) Voluntary muscle activation. (C) Maximal relaxation rate. (D) Maximal rate of force development. (E) Resting potentiated twitch in percentual values. (F) Resting potentiated twitch in absolute values after fatigue. Values are presented as Mean ± SEM; *: p < 0.05.

Figure 5

Central hemodynamic (Heart rate (HR); Cardiac output (CO); Panel (A,B)). Oxygen consumption (VO₂; Panel (C)) and perceived exertion (RPE; Panel (D)) throughout the time to exhaustion (TTE) under Placebo (PL) and Capsaicin (CAP) Conditions (n = 10). In panel (D), RPE is represented as the rating of perceived exertion of the lower limbs (RPEleg; triangle) and whole-body (RPEtot; dot). Values are presented as Mean ± SEM.