Effect of Nitrate Supplementation on Delayed Onset Muscle Soreness Indices: A Double-Blind, Randomized, Cross-Over...

Delayed onset muscle soreness (DOMS) results from unaccustomed exercise, leading to pain, decreased muscle force, and limited joint range of motion (ROM). Nitrate supplementation may alleviate these symptoms. The aim of this study was to evaluate the impact of potassium nitrate on muscle tenderness, isometric force, and elbow ROM following eccentric exercise.

This double-blind, randomized, crossover clinical trial was conducted at Imam Khomeini Hospital, Tehran, Iran, during 2023. Participants (sedentary adults aged 18-40) ingested 1000 mg of potassium nitrate or a placebo (Stevia) 3 hours prior to performing eccentric biceps curls. Assessments included tenderness (Visual Analogue Scale), force (kilogram force), and ROM (degrees) at baseline, 48 hours, and 96 hours post-exercise. A minimum one-week washout period separated the interventions. Data were analyzed using non-parametric repeated-measures models in R software version 4.5.0 (significance set at P<0.05).

Sixteen participants completed both arms of the crossover study. Median (IQR) tenderness scores for potassium nitrate were 20 (39) at baseline, 26.5 (45.5) at 48 hours, and 22 (36.75) at 96 hours, compared to 21 (36.75), 49.5 (26.25), and 32 (42.75) for the placebo. Nitrate reduced tenderness over time compared to the placebo (P<0.001). The p-values for the time-treatment interaction were P=0.05 for Wald-type statistics and P=0.06 for ANOVA-type statistics. Post-hoc testing confirmed lower pain in the nitrate group at 96 hours post-exercise (P=0.03). No significant between-group differences were found for isometric force or ROM (P>0.05).

A single dose of potassium nitrate supplementation before eccentric exercise significantly reduced muscle tenderness but had no effect on muscle force or joint ROM.