Lack of effect of superficial heat to the knee on quadriceps function in individuals with quadriceps inhibition.

CONTEXT Quadriceps function improves after application of focal joint cooling or transcutaneous electrical nerve stimulation to the knee in patients with arthrogenic muscle inhibition (AMI), yet it is not known whether superficial heat is able to produce a similar effect. OBJECTIVE To determine quadriceps function after superficial heat to the knee joint in individuals with AMI. DESIGN Single blinded randomized crossover. SETTING Laboratory. PATIENTS 12 subjects (4 female, 8 males; 25.6 ± 7.7 y, 177.2 ± 12.7 cm, 78.4 ± 18.2 kg) with a history of knee-joint pathology and AMI, determined with a quadriceps central activation ratio (CAR) of <90%. INTERVENTION 3 treatment conditions for 15 min on separate days: superficial heat using a cervical moist-heat pack (77 °C), sham using a cervical moist pack (room temperature at about 24 °C), and control (no treatment). All subjects received all treatment conditions in a randomized order. MAIN OUTCOME MEASURES Central activation ratio and knee-extension torque during maximal voluntary isometric contraction with the knee flexed to 60° were collected at pre, immediately post, 30 min post, and 45 min posttreatment. Skin temperature of the quadriceps and knee and room temperature were also recorded at the same time points. RESULTS Three (treatment conditions) by 4 (time) repeated ANOVAs found that there were no significant interactions or main effects in either CAR or knee-extension torque (all P > .05). Skin-temperature 1-way ANOVAs revealed that the skin temperature in the knee during superficial heat was significantly higher than other treatment conditions at all time points (P < .05). CONCLUSIONS Superficial heat to the knee joint using a cervical moist-heat pack did not influence quadriceps function in individuals with AMI in the quadriceps.