Effects of Two Cooling Modalities on Temperature Recovery on Rectal, Middle Gluteal, and Pectoral Muscle Temperature Recovery Following Treadmill Exercise
Rectal temperature is the most common method used to measure body temperature in horses post-exercise. Recently, percutaneous thermal-sensing microchips (PTSM) have been used to measure temperature in the pectoral (PECT) and middle gluteal (GLUT) muscles of horses before, during, and after exercise1,2,3. The objective of this study was to compare the effects of hosing or walking on recovery of RECTAL, GLUT, and PECT temperatures in exercised horses.
Eight mature Thoroughbreds with PTSM previously implanted in the GLUT and PECT were used in a two-week cross-over design study. Following a 15-min standardized exercise test on an inclined (3o) high-speed treadmill (max speed 10 m/s @ HR 200.16.8 bpm), horses were either hosed for 5 min then walked for 10 min (HOSE) or walked for 15 min (WALK). Horses then stood in stalls with fans from 15 to 60 min post-exercise. Rectal, GLUT, and PECT temperatures were collected immediately before and after exercise, then at pre-determined intervals until 60 min of recovery. Changes from pre-exercise temperatures for GLUT, and PECT were fitted to an exponential one phase decay model to determine logarithmic rate of heat dissipation and expressed as cooling half-life (t1/2) in minutes. Differences in t1/2 between treatments were analyzed using a paired student’s t-test. Other temperature data were analyzed using a repeated measures two-way ANOVA. Results are reported as mean ± SD and considered significant at P < 0.05.
Post-exercise GLUT and PECT temperatures were 40.6±0.4oC and 40.8±0.5oC, respectively while RECTAL only reached a post-exercise temperature of 39.2±0.50oC. RECTAL temperature increased less (1.36±0.46oC) compared to pre-exercise than either GLUT (3.00±0.50oC) or PECT (3.79±0.48oC) temperatures (P<.001). HOSE decreased GLUT and PECT temperatures compared to WALK from 10 min until 30 min post-exercise (P<0.05). RECTAL temperature during WALK did not differ at any time compared to HOSE. Both GLUT and PECT t1/2 were shorter for HOSE (12.74±5.78 min and 13.97±2.98 min) than WALK (22.57±9.93 min and 18.50±4.92 min) (P < 0.05).
Hosing immediately post-exercise effectively shortened both GLUT and PECT temperature recovery rates. Rectal temperature post-exercise was lower than GLUT and PECT temperatures and was unaffected by hosing. PTSM implanted in GLUT and PECT produced no adverse reactions and offer an attractive alternative to rectal temperatures to more accurately monitor muscle recovery.
References:
1Kang et al. 2020. Animals 10 (12), 2274.
2Kang et al. 2022. Animals 12 (10), 1267.
3Kang et al. 2023. Intern. J. Biomet. 67 (6), 957-973