Health, Exercise, and Sports Sciences ETDs

Publication Date

Fall 11-13-2020


Purpose: The purpose of this study was to investigate the combined effect of downhill running and heat stress on muscle damage, as well as on heat strain and kidney stress during subsequent endurance exercise in the heat. Methods: Using a crossover design and randomized order, ten non-heat-acclimated, physically active males completed downhill running in a cool (EIMD in Cool) and hot (EIMD in Hot) environment followed by an exercise-heat stress (HS) test after 3-hour seated rest. Core temperature, heart rate, thermal sensation and ratings of perceived exertion were recorded throughout each exercise session. Blood and urine samples were collected at immediately before (pre-) and after (post-) EIMD and HS, and 24 hours post-EIMD (post-24h). Serum creatine kinase (CK) activity, maximal voluntary isometric contraction of the quadriceps (MVC) and perceived muscle soreness were recorded to evaluate muscle damage. Urinary neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1) levels were measured to indicate acute kidney stress. Results: By the end of the EIMD sessions, the Hot condition induced a significantly higher core temperature (EIMD in Hot: 38.75 ± 0.35° C; EIMD in Cool: 38.27 ± 0.38° C, p = 0.04) and heart rate (EIMD in Hot: 157 ± 19 bpm; EIMD in Cool: 140 ± 15 bpm, p = 0.035). There was no difference in CK, MVC or perceived soreness between the conditions at any timepoints. Urinary NGAL level was significantly elevated in EIMD in Hot condition at post-HS comparing with pre-HS (pre-HS: 6.56 {1.53 – 12.24} ng/min, post-HS: 13.72 {7.67 – 21.46} ng/min p = 0.034). Conclusions: Downhill running combined with heat stress does not seem to aggravate muscle damage, compared with downhill running in a temperate condition. Nevertheless, prior EIMD in a hot environment may pose a greater risk of acute kidney injury during subsequent endurance exercise in the heat.


exercise-induced muscle damage. exertional heat stroke, acute kidney injury, downhill running

Document Type




Degree Name

Physical Education, Sports and Exercise Science

Level of Degree


Department Name

Health, Exercise, and Sports Sciences

First Committee Member (Chair)

Fabiano Amorim

Second Committee Member

Christine Mermier

Third Committee Member

Flavio de Castro Magalhaes

Fourth Committee Member

Matthew Kuennen