Unilateral Quadriceps Strengthening With Disinhibitory Cryotherapy and Quadriceps Symmetry After Anterior Cruciate Ligament Reconstruction

Abstract

Context:  The effect of unilateral cryotherapy-facilitated rehabilitation exercise on involved-limb quadriceps function and limb symmetry in individuals with quadriceps dysfunction after anterior cruciate ligament reconstruction (ACLR) remains unclear. Objective:  To measure the effect of a 2-week unilateral cryotherapy-facilitated quadriceps-strengthening program on knee-extension strength and quadriceps central activation ratio (CAR) in participants with ACLR. Design:  Controlled laboratory study. Setting:  Laboratory. Patients or Other Participants:  A total of 10 volunteers with unilateral ACLR (1 man, 9 women; age = 21.0 ± 2.8 years, height = 164.6 ± 5.0 cm, mass = 64.0 ± 6.1 kg, body mass index = 23.7 ± 2.7 kg/m2) and 10 healthy volunteers serving as control participants (1 man, 9 women; age = 20.8 ± 2.5 years, height = 169.1 ± 6.2 cm, mass = 61.1 ± 6.4 kg, body mass index = 21.4 ± 2.3 kg/m2) participated. Intervention(s):  Participants with ACLR completed a 2-week unilateral cryotherapy-facilitated quadriceps-strengthening intervention. Main Outcome Measure(s):  Bilateral normalized knee-extension maximal voluntary isometric contraction (MVIC) torque (Nm/kg) and quadriceps CAR (%) were assessed preintervention and postintervention. Limb symmetry index (LSI) was calculated at preintervention and postintervention testing. Preintervention between-groups differences in unilateral quadriceps function and LSI were evaluated using independent-samples t tests. Preintervention-to-postintervention differences in quadriceps function were evaluated using paired-samples t tests. Cohen d effect sizes (95% confidence interval [CI]) were calculated for each comparison. Results:  Preintervention between-groups comparisons revealed less knee-extension MVIC torque and quadriceps CAR for the ACLR limb (MVIC: P = .01, Cohen d = −1.31 [95% CI = −2.28, −0.34]; CAR: P = .004, Cohen d = −1.48 [95% CI = −2.47, −0.49]) and uninvolved limb (MVIC: P = .03, Cohen d = −1.05 [95% CI = −1.99, −0.11]; CAR: P = .01, Cohen d = −1.27 [95% CI = −2.23, −0.31]) but not for the LSI (MVIC: P = .46, Cohen d = −0.34 [95% CI = −1.22, 0.54]; CAR: P = .60, Cohen d = 0.24 [95% CI = −0.64, 1.12]). In the ACLR group, participants had improved knee-extension MVIC torque in the involved limb (P = .04, Cohen d = 0.32 [95% CI = −0.56, 1.20]) and uninvolved limb (P = .03, Cohen d = 0.29 [95% CI = −0.59, 1.17]); however, the improvement in quadriceps CAR was limited to the involved limb (P = .02, Cohen d = 1.16 [95% CI = 0.21, 2.11]). We observed no change in the LSI with the intervention for knee-extension MVIC torque (P = .74, Cohen d = 0.09 [95% CI = −0.79, 0.97]) or quadriceps CAR (P = .61, Cohen d = 0.26 [95% CI = −0.62, 1.14]). Conclusions:  Two weeks of cryotherapy-facilitated exercise may improve involved-limb quadriceps function while preserving between-limbs symmetry in patients with a history of ACLR.