This study aimed to determine the effect of cooling progressively greater portions of the lower extremities on dynamic balance and neuromuscular activation.Methods
Ten healthy males (22.8 ± 3.4 yr, 76.5 ± 9.1 kg) performed one room air temperature control (22.4°C ± 0.8°C) and three trials of cold water immersion at 12°C (lateral malleolus, ankle; lateral femoral epicondyle, knee; anterior superior iliac spine, hip) for 10 min before performing a unipedal balance test (Star Excursion Balance Test (SEBT)) with their dominant limb. Muscle activation of the vastus lateralis, biceps femoris, tibialis anterior, and lateral gastrocnemius was measured with surface EMG during the SEBT.Results
Core temperature remained euthermic throughout all trials. Gastrocnemius temperature decreased from control (30.4°C ± 0.5°C) with knee (23.7°C ± 1.7°C) and hip immersion (22.4°C ± 1.0°C), whereas vastus lateralis temperature decreased from control (33.7°C ± 1.7°C) with hip immersion (27.3°C ± 2.0°C) (P < 0.01 for all comparisons). Cold water immersion influenced mean anterior and posterior reach distance on the SEBT in a dose-dependent fashion. Compared with those in control, mean anterior and posterior SEBT reach distances were not decreased with ankle (−1.38% and −0.74%, respectively) and knee immersion (−2.48% and −2.74%), whereas hip immersion significantly reduced SEBT by 4.73% and 4.05% (P < 0.05, d = 0.52–0.58). Muscle activation was largely unaffected as the lower extremities were cooled, with only the lateral gastrocnemius during the anterior SEBT approaching a decrease (P = 0.059).Conclusions
Cooling larger portions of the lower extremities progressively affect dynamic balance, and thermal protection strategies should focus on maintaining temperature in the large muscle mass of the thigh.