Pre-operative quadriceps activation is related to post-operative activation, not strength, in patients post-ACL reconstruction

Abstract

Purpose

Quadriceps activation failure is considered to contribute to the weakness that lingers following anterior cruciate ligament (ACL) reconstruction. Importantly, the impact of pre-operative quadriceps activation on post-operative quadriceps function is unknown. Understanding this relationship is clinically important; as the counteractive approach clinicians should employ pre-operatively to mitigate post-operative quadriceps weakness is unclear. Accordingly, the primary purpose of this study was to investigate the relationship between pre-operative quadriceps activation and post-operative quadriceps strength and activation.

Methods

Fifty-four individuals post-ACL injury reported for testing on two occasions: prior to surgery and post-surgery once they returned to activity. Quadriceps activation was assessed using the burst superimposition technique and quantified using the central activation ratio. Quadriceps strength was assessed using isometric contractions that were performed at 90° of knee flexion. Multiple linear regressions were utilized to detect the relationships between pre-operative activation and strength and post-operative activation and strength.

Results

Pre-operative activation was not associated with post-operative strength (R ² = 0.064, P = 0.186). Pre-operative quadriceps activation and strength were associated with post-operative activation (R ² = 0.383, P ≤ 0.001) and strength (R ² = 0.465, P ≤ 0.001), respectively.

Conclusions

Individuals with better pre-operative quadriceps activation demonstrated greater post-operative activation. Similarly, individuals with better pre-operative strength demonstrated better post-operative strength. Pre-operative quadriceps activation was not a predictor of post-operative strength. From a clinical perspective, our work indicates that clinicians should utilize therapies targeting both quadriceps activation and strength prior to ACL reconstruction in order to maximize these factors post-ACL reconstruction, as pre-operative activation and strength are related to post-operative activation and strength, respectively at return-to-activity.

Appendices

Appendix 1

See Table 3.

Table 3 Post-operative Guidelines for Participants Undergoing ACL Reconstruction

Appendix 2: Clinic specific return to play criteria

To be cleared for activity all participants were required to complete a leg press test and basic three-week agility program.

Leg press test

To pass the leg press test, the clinical protocols require that patients need to complete at least 15 repetitions at 100 % of body weight with the involved limb from a resting neutral position to a depth of 90° of knee flexion. This test is performed while subjects are in a recumbent, supine position with their ACL limb in contact with the platform. No other strength tests are utilized by the clinic for

Agility program guidelines

Directions: complete three sessions per week with at least 1 day of rest in between sessions. Do not complete a session if you are experiencing pain or swelling. Take rest days until symptoms are gone, and then resume the program. If you are performing your strength workout on the same day as your agility workout, make sure you perform you strength workout last.

Exercise	Week
	1	2	3
Forward run	10 reps	10 reps	10 reps
Retro run	10 reps	10 reps	10 reps
Side shuffles	10 reps	10 reps	10 reps
Carioca’s	10 reps	10 reps	10 reps
Forward skip	10 reps	10 reps	10 reps
Retro skip	10 reps	10 reps	10 reps
Quick step		5 reps × 20 s	5 reps × 20 s
Double leg line hop		5 reps × 20 s	5 reps × 20 s
Double leg square hop		5 reps × 20 s	5 reps × 20 s
Cutting			10 reps (1/2 basketball court)
Shuttle run			10 reps (full basketball court)
Box cut			10 reps (each corner basketball court)
Base running			10 reps (on baseline of court, forward and backward)

Agility exercise descriptions

Side shuffles

In a defensive stance, run sideways (laterally) with trailing foot stepping to the leading foot.

Carioca’s

Run sideways (laterally) by alternately crossing trailing leg in front of the leading leg and then crossing trailing leg behind the leading leg.

Quick step

Place a line on the floor. On toes, quickly step forward over the line with both feet, then step backward over the line, emphasizing quickness.

Double leg line hop

Place a line on the floor. Start on one side of the line with feet parallel to the line. Hop with both feet to the opposite side of the line and then hop back to the starting position.

Double leg square hop

Form a cross on the floor with tape. As you are facing the cross, box 1 is lower left, box 2 is upper left, box 3 is upper right, and box 4 is lower right. Start in box 1, with both feet hop forward to box 2, then hop laterally to box 3, then hop backward to box 4, then hop laterally back to box 1. Week 2 of agilities perform this pattern: 1, 2, 3, 4. Week 3 of agilities, switch to this pattern: 1, 3, 2, 4.

Cutting

Run at a 45° angle for 3–5 steps. Plant on the outside leg and cut 90° and continue another 3–5 steps. Continue this zig-zag pattern to half-court (basketball) or about 18 m (20 yards).

Shuttle runs

Perform either on a basketball court or outside, about 36 m (40 yards) total distance. Start on the baseline, run and touch the free-throw line, then return and touch the baseline. Next, run and touch half-court, then back and touch. Then run and touch the opposite free-throw line, then back and touch. Finally, run and touch the opposite baseline, then back and touch. Outside, go 9 m (10 yards), back, 18 m (20 yards), back, 27 m (30 yards), back, and 36 m (40 yards), back.

Box cut

Use the basketball key or similar size area. Start on the baseline at one of the corners. Run forward to the free-throw line. Change direction on your outside leg and side shuffle across the free-throw line. Plant on your outside leg and run backward to the baseline. Change direction on your outside leg and side shuffle back to your starting position. Repeat beginning from the opposite corner you started from.

Base running

Use softball or little league bases. If you are inside, just use half a basketball court. Starting from home plate, run bases with rounded turns like you normally would. Repeat in the opposite direction.