Effects of different phenylcapsaicin doses on resistance training performance, muscle damage, protein breakdown, metabolic response, ratings of perceived exertion, and recovery: a randomized, triple-blinded, placebo-controlled, crossover trial

ABSTRACT

Background

The aim of this study was to explore the effects of a low dose (LD) of 0.625 mg and a high dose (HD) of 2.5 mg of phenylcapsaicin (PC) on full squat (SQ) performance, active muscle (RPE-AM) and overall body (RPE-OB) ratings of perceived exertion, muscle damage, protein breakdown, metabolic response, and 24-h recovery in comparison to placebo (PLA).

Method

Twenty-five resistance-trained males (age = 21.00 ± 2.15 years, SQ 1-repetition maximum [1RM] normalized = 1.66 ± 0.22 kg) were enrolled in this randomized, triple-blinded, placebo-controlled, crossover trial. Participants completed 2 weekly sessions per condition (LD, HD, and PLA). The first session consisted of pre-blood testing of lactate, urea, and aspartate aminotransferases (AST) and 2 SQ repetitions with 60% 1RM followed by the resistance exercise protocol, which consisted of SQ sets of 3 × 8 × 70% 1RM monitoring lifting velocity. RPE-OB and RPE-AM were assessed after each set. After the first session, 2 SQ repetitions with 60% 1RM were performed, and blood lactate and urea posttests were collected. After 24 h, AST posttest and 1 × 2 × 60% 1RM were determined as biochemical and mechanical fatigue outcomes.

Results

HD reported significant differences for RPE-AM, AST, and SQ performance compared to LD and PLA. Post-hoc analyses revealed that HD attained faster velocities in SQ than LD (p = 0.008). HD induced a lower RPE-AM when compared with LD (p = 0.02) and PLA (p = 0.004). PLA resulted in higher AST concentrations at 24-h post than HD (p = 0.02). No significant differences were observed for the rest of the comparisons.

Conclusions

This study suggests that PC may favorably influence SQ performance, RPE-AM, and muscle damage compared to PLA. However, HD exhibited most of the biochemical and mechanical anti-fatigue effects instead of LD.

KEYWORDS:

• TRPV1
• ergogenic aid
• capsaicinoids
• velocity-based training
• velocity loss

Acknowledgments

We would like to thank all the participants involved in this study and Axichem for supporting us with scientific material. We also acknowledge AMG., MC, and Life Pro Nutrition for their involvement on the preparation of the blinded packages.

Disclosure statement

PJM and CAF are scientific advisors of a supplement brand (Life Pro Nutrition, Madrid, Spain).

Data availability statement

Datasets used in this study are available from the corresponding author under reasonable request.

Publication statement

This manuscript has not been published elsewhere.

Authors´ contributions

The study and methodology were conceived using JCC, PJM, FPB, and CAF. PCD, JSV, IAI, CCC, PJM were involved in data collection and data treatment, writing was conducted by CAF and PJM, all authors reviewed critically the manuscript under JCC and FPB supervision.

Additional information

Funding

This study was supported by Axichem. However, the sponsor was not involved in data collection or data entry, and there were no restrictions on analysis, writing, or publication.