The effects of Shilajit supplementation on fatigue-induced decreases in muscular strength and serum hydroxyproline levels

Abstract

Background

Shilajit is a safe, fluvic mineral complex exudate that is common to Ayurvedic medicine and is composed of fulvic acids, dibenzo-α-pyrones, proteins, and minerals. The purpose of this study was to examine the effects of 8 weeks of Shilajit supplementation at 250 mg·d^− 1 (low dose) and 500 mg·d^− 1 (high dose) versus placebo on maximal voluntary isometric contraction (MVIC) strength, concentric peak torque, fatigue-induced percent decline in strength, and serum hydroxyproline (HYP).

Methods

Sixty-three recreationally-active men ($\overline{X}$ ± SD: 21.2 ± 2.4 yr.; 179.8 ± 6.3 cm; 83.1 ± 12.7 kg) volunteered to participate in this study. The subjects were randomly assigned to the high dose, low dose, or placebo group (each group: n = 21). During pre-supplementation testing, the subjects performed 2 pretest MVICs, 2 sets of 50 maximal, bilateral, concentric isokinetic leg extensions at 180°·s^− 1 separated by 2-min of rest, and 2 posttest MVICs. Following 8 weeks of supplementation, the subjects repeated the pre-supplementation testing procedures. In addition, the groups were dichotomized at the 50th percentile based on pre-supplementation MVIC and baseline HYP. Mixed model ANOVAs and ANCOVAs were used to statistically analyze the dependent variables for the total groups (n = 21 per group) as well as dichotomized groups.

Results

For the upper 50th percentile group, the post-supplementation adjusted mean percent decline in MVIC was significantly less for the high dose group (8.9 ± 2.3%) than the low dose (17.0 ± 2.4%; p = 0.022) and placebo (16.0 ± 2.4%; p = 0.044) groups. There was no significant (p = 0.774) difference, however, between the low dose and placebo groups. In addition, for the upper 50th percentile group, the adjusted mean post-supplementation baseline HYP for the high dose group (1.5 ± 0.3 μg·mL^− 1) was significantly less than both the low dose (2.4 ± 0.3 μg·mL^− 1; p = 0.034) and placebo (2.4 ± 0.3 μg·mL^− 1, p = 0.024) groups.

Conclusions

The results of the present study demonstrated that 8 weeks of PrimaVie® Shilajit supplementation at 500 mg·d^− 1 promoted the retention of maximal muscular strength following the fatiguing protocol and decreased baseline HYP. Thus, PrimaVie® Shilajit supplementation at 500 mg·d^− 1 elicited favorable muscle and connective tissue adaptations.

Keywords:

• Shilajit
• Muscular strength
• Collagen
• Hydroxyproline
• Fatigue

Acknowledgements

We would like to thank all the subjects for their participation. In addition, we would like to thank Dr. Sophie Alvarez and technicians of the Proteomics and Metabolomics Facility at the Center for Biotechnology/ University of Nebraska - Lincoln for their contribution.

Funding

The project was funded by Natreon Inc.

Availability of data and materials

Individual data not available due to the University’s Institution Review Board regulations. Please contact authors for all other data requests.

Authors’ contributions

All authors participated in the conception and design of the study. JLK, ECH, and CMS collected data and recruited subjects. JLK and TJH wrote the manuscript. JLK, ECH, and CMS carried out all dietary analyses. All authors equally contributed to the data analysis. All authors gave approval of the final manuscript, and they were equally involved in the editing and revising of the final manuscript draft.

Ethics approval and consent to participate

The University of Nebraska Institutional Review Board for Human Subjects approved the study (IRB Approval #: 20171117645FB).

Consent for publication

Not applicable; no individual data was reported.

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.