en Sports and Exercise Medicine Sports and Exercise Medicine Original Research Original Research <span style="font-size:13pt"><span style="text-justify:kashida"><span style="text-kashida:0%"><span style="text-autospace:none"><span style="font-family:&quot;Times New Roman&quot;,serif"><span style="font-style:italic"><b><span style="font-size:9.0pt"><span style="font-style:normal">Background: </span></span></b><span style="font-size:9.0pt"><span style="font-style:normal">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. </span></span></span></span></span></span></span></span><br> <span style="font-size:13pt"><span style="text-justify:kashida"><span style="text-kashida:0%"><span style="text-autospace:none"><span style="font-family:&quot;Times New Roman&quot;,serif"><span style="font-style:italic"><span style="font-size:9.0pt"><span style="font-style:normal">&nbsp;&nbsp; <b>Methods:</b> 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 </span></span><span style="font-size:9.0pt">P</span><span style="font-size:9.0pt"><span style="font-style:normal"><0.05). </span></span></span></span></span></span></span></span><br> <span style="font-size:13pt"><span style="text-justify:kashida"><span style="text-kashida:0%"><span style="text-autospace:none"><span style="font-family:&quot;Times New Roman&quot;,serif"><span style="font-style:italic"><span style="font-size:9.0pt"><span style="font-style:normal">&nbsp;&nbsp; <b>Results:</b> 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 (</span></span><span style="font-size:9.0pt">P</span><span style="font-size:9.0pt"><span style="font-style:normal"><0.001). The p-values for the time-treatment interaction were </span></span><span style="font-size:9.0pt">P</span><span style="font-size:9.0pt"><span style="font-style:normal">=0.05 for Wald-type statistics and </span></span><span style="font-size:9.0pt">P</span><span style="font-size:9.0pt"><span style="font-style:normal">=0.06 for ANOVA-type statistics. Post-hoc testing confirmed lower pain in the nitrate group at 96 hours post-exercise (</span></span><span style="font-size:9.0pt">P</span><span style="font-size:9.0pt"><span style="font-style:normal">=0.03). No significant between-group differences were found for isometric force or ROM (</span></span><span style="font-size:9.0pt">P</span><span style="font-size:9.0pt"><span style="font-style:normal">>0.05).</span></span></span></span></span></span></span></span><br> <span style="font-size:13pt"><span style="text-justify:kashida"><span style="text-kashida:0%"><span style="text-autospace:none"><span style="font-family:&quot;Times New Roman&quot;,serif"><span style="font-style:italic"><span style="font-size:9.0pt"><span style="font-style:normal">&nbsp;&nbsp; <b>Conclusion:</b> A single dose of potassium nitrate supplementation before eccentric exercise significantly reduced muscle tenderness but had no effect on muscle force or joint ROM. </span></span></span></span></span></span></span></span><br> &nbsp; Nitrates, Musculoskeletal Pain, Muscle Force, Joint Range Of Motion, Sports Medicine 345 354 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-10035-1&slc_lang=en&sid=1 Mohammad Mahdi Tavana tavana.md@yahoo.com 200319475328460097404 200319475328460097404 No Department of Sports and Exercise Medicine, Imam Khomeini Hospital Complex, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran Farzin Halabchi fhalabchi@tums.ac.ir 200319475328460097405 200319475328460097405 Yes Department of Sports and Exercise Medicine, Imam Khomeini Hospital Complex, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran Tohid Seif Barghi tohid_seif@yahoo.com 200319475328460097406 200319475328460097406 No Department of Sports and Exercise Medicine, Imam Khomeini Hospital Complex, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran Reyhaneh Khazaei reyhanehkh72@gmail.com 200319475328460097407 200319475328460097407 No Department of Sports and Exercise Medicine, Imam Khomeini Hospital Complex, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran Shaghayegh Rahimi shaqayeq.rahimi@yahoo.com 200319475328460097408 0009-0007-2777-3782 No Department of Sports and Exercise Medicine, Imam Khomeini Hospital Complex, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran