Acute responses and recovery in the femoral cartilage morphology following running and cool-down protocols

This study compared the immediate effects of two common post-exercise cool-down methods to a control condition on subsequent morphologic change in femoral cartilage and vascular response in the posterior tibial artery after running. Sixteen healthy young males (23.6 ± 2.2 years, 172.8 ± 4.9 cm, 72.2 ± 7.1 kg) visited the laboratory during three separate sessions and performed 30-min of treadmill running (7.5 km/h for the initial 5-min, followed 8.5 km/h for 25-min). After running, participants experienced one of three 30-min cool-down protocols: active cool-down, cold application, or control (seated rest with their knee fully extended), in a counterbalanced order. Ultrasonographic assessments of femoral cartilage thickness (intercondylar, lateral, and medial) and posterior tibial artery blood flow were compared. To test condition effects over time, two-way analysis of variances and Tukey tests were used (<i>p</i> < 0.05) with Cohen's d effect sizes (ES). There was no condition by time interaction in femoral cartilage thickness (intercondylar: F_30,705 = 0.91, <i>p</i> = 0.61; lateral: F_30,705 = 1.24, <i>p</i> = 0.18; medial: F_30,705 = 0.49, <i>p</i> = 0.99). Regardless of time (condition effect: F_2,705 > 3.24, <i>p</i> < 0.04 for all tests), femoral cartilage in the cold application condition was thicker than the control condition (intercondylar: <i>p</i> = 0.01, ES = 0.16; lateral: <i>p</i> < 0.0001, ES = 0.24; medial: <i>p</i> = 0.04. ES = 0.16). Regardless of condition (time effect: F_15,705 > 10.31, <i>p</i> < 0.0001 for all tests), femoral cartilage thickness was decreased after running (intercondylar: <i>p</i> < 0.0001, ES = 1.37; lateral: <i>p</i> < 0.0001, ES = 1.58; medial: <i>p</i> < 0.0001, ES = 0.81) and returned to baseline levels within 40-min (intercondylar: <i>p</i> = 0.09; lateral: <i>p</i> = 0.64; medial: <i>p</i> = 0.26). Blood flow volume was different (condition × time: F_30,705 = 2.36, <i>p</i> < 0.0001) that running-induced blood flow volume was maintained for 30-min for the active cool-down condition (<i>p</i> < 0.0001, ES = 1.64), whereas it returned to baseline levels within 10-min for other conditions (cold application: <i>p</i> = 0.67; control: <i>p</i> = 0.62). Neither blood flow nor temperature had a significant impact on the recovery in femoral cartilage after running.