Eccentric knee flexor torque following anterior cruciate ligament surgery

Quadriceps Strength and Endurance After Posterior Cruciate Ligament Tears Versus Matched Group With Anterior Cruciate Ligament Tears

PURPOSE

This study was designed to compare the preoperative strengths and endurances of the quadriceps and hamstring muscles in patients with anterior cruciate ligament (ACL) versus posterior cruciate ligament (PCL) tears.

METHODS

Quadriceps and hamstring muscle strength and endurance were compared between 20 prospectively enrolled patients with isolated PCL tears and a retrospective, matched control group of 20 patients with isolated ACL tears. The maximal torque (60°/s) and total work (180°/s) of the quadriceps and hamstring were evaluated with an isokinetic testing device.

RESULTS

Total work (1,094.4 ± 505.8 J v 797.5 ± 332.7 J, P = .035) and peak torque (129.9 ± 56.2 N ∙ m v 98.2 ± 37.4 N ∙ m, P = .046) of the quadriceps muscle on the involved side were higher in the PCL tear group than in the ACL tear group. However, there were no significant differences between the PCL tear group and ACL tear group in hamstring muscle strength (45.8 ± 42.3 N ∙ m and 46.0 ± 24.4 N ∙ m, respectively; P = .940) and endurance (429.3 ± 238.9 J and 382.4 ± 256.1 J, respectively; P = .574) on the involved side.

CONCLUSIONS

The strength and endurance of the quadriceps muscle of the injured limb were greater after PCL tears than after ACL tears. However, there were no significant between-group differences in hamstring muscle strength and endurance on the involved side.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Intérêts des évaluations isocinétiques du genou avant et après reconstruction du ligament croisé antérieur chez le footballeur

AIM

The aim of this study was to analyse the evolution of the isokinetic performance of the knee flexor and extensor muscles in soccer players before and after intra-articular anterior cruciate ligament reconstruction (Kennet-Jones).

METHODS

Two isokinetic evaluations were carried out before surgery and after rehabilitation (i.e. 4 months later) in 18 soccer players.

RESULTS

The initial evaluation showed that the stabilizing muscles of the knee were affected differently after lesion of the external anterior crossed ligament. At the opposite of the flexor muscles, the performance of the knee extensor muscles of the injured leg was significantly reduced as compared with that of the healthy leg (peak torque at 90 degrees /s, -16%; power at 180 degrees /s, -14%; total work at 240 degrees /s, -11%). Even if 4 months after surgery, this deficit was accentuated (peak torque at 90 degrees /s, -26%; power at 180 degrees /s, -23%; total work at 240 degrees /s, -19%), the preoperative results of the knee extensor muscle do not condition the postoperative performance.

CONCLUSION

After a rupture of the external anterior crossed ligament, a regular program of isokinetic evaluation of the knee seems to be relevant in the follow-up of the wounded athlete. The evaluation before surgery can be used as reference, and from a psychological point of view, this evaluation can create confidence in the athlete during hospitalization. A second evaluation 4 months after surgery can be used to quantify the muscular deficit to direct the exercises of rehabilitation.

Spectral EMG changes in vastus medialis muscle following short range of motion isokinetic training

This study was aimed at exploring the carryover effect of short range of motion (RoM) isokinetic conditioning on vastus medialis (VM) motor unit recruitment (MUR) across the full RoM. Fifty-five women were randomly assigned to one of four groups: G1 (n = 14) and G2 (n = 14) trained concentrically at 30 and 90 degrees /s, respectively whereas G3 (n = 13) and G4 (n = 14) trained similarly but using the eccentric mode. All 4 groups trained within 30-60 degrees of knee flexion. The training protocol consisted of 4 sets of 10 maximal repetitions, 3 times a week for 6 weeks. sEMG was recorded from the VM for analysis of mean frequency of the EMG power spectrum prior to the training period and 2 days after its termination. The EMG assessments took place during dynamic contractions within 3 angular RoM's: 85-60 degrees (R1), 60-30 degrees (R2) and 30-5 degrees (R3). In addition MUR was evaluated during isometric contractions at 10 degrees , 45 degrees and 80 degrees . Significant increases were observed in the MUR at R1, R2, and R3 during dynamic contractions as well as in all 3 angles during isometric contractions. These findings applied equally regardless of the mode of contraction and motion speed during training. The fact that MUR increased significantly within untrained RoM's may point out to the potential benefits of short RoM conditioning, particularly in those cases where, during specific phases of rehabilitation, a wider RoM may be contraindicative.

Transferability of Strength Gains from Limited to Full Range of Motion

PURPOSE

This study was aimed at exploring the transferability of short range of motion (RoM) isokinetic conditioning on quadriceps performance inside and outside the trained range.

METHODS

Fifty-five women were randomly assigned to one of four groups: G1 (N = 14) and G2 (N = 14) trained concentrically at 30 and 90degrees x s(-1), respectively, whereas G3 (N = 13) and G4 (N = 14) trained similarly but using the eccentric mode. All four groups trained within 30-60degrees of knee flexion. The training paradigm consisted of 4 sets of 10 maximal repetitions, 3x wk(-1) for a total period of 6 wk. Before the training period and 2 d after its termination, the isokinetic work output (Wisk) was assessed within three angular RoM: 85-60degrees (R1), 60-30degrees (R2), and 30-5degrees (R3). Isometric peak extension moment (PM) and rate of force development (RFD) were evaluated at 10degrees, 45degrees and 80degrees.

RESULTS

Significant increases were observed in the isometric output (at all three angles), Wisk (in R1 and R2), and the RFD (45degrees). The PM increased significantly more in G3 and G4 compared with G1 and G2, evidencing specificity of contraction mode.

CONCLUSION

These findings point out to the potential benefits of short RoM conditioning, particularly in those cases where, during specific phases of rehabilitation, a wider RoM may be contraindicative.

Évaluation isocinétique des extenseurs et fléchisseurs du genou en médecine du sport : revue de la littérature

There is growing evidence that isokinetic muscle strength, is one of the most common testing method why muscle strength is thought to be a major factor in athletic success and rehabilitation. A lot of publications during the last 20 years concerned the peak torque, the concentric ratio flexor/extensor, with comparison between males and females, sport specialties, young and old people. Isokinetic is also used for evaluation of knee disorders. The results are very useful after knee ligament surgery, less for femoro-patellar disorders and arthrosis. More recently some authors proposed the functional concept (eccentric flexors/concentric extensors ratio) as a predictive method for preventive muscle injuries or ACL lesions. They demonstrated more discomfort after muscle disorders with isokinetic eccentric testing, and proposed rehabilitation programs for prevention. However apart from a few situations, isokinetic testing does not fully predict functional measurements. It must be used with other techniques of evaluation (clinical methods and imagery).

Eccentric muscle contractions: their contribution to injury, prevention, rehabilitation, and sport

Muscles operate eccentrically to either dissipate energy for decelerating the body or to store elastic recoil energy in preparation for a shortening (concentric) contraction. The muscle forces produced during this lengthening behavior can be extremely high, despite the requisite low energetic cost. Traditionally, these high-force eccentric contractions have been associated with a muscle damage response. This clinical commentary explores the ability of the muscle-tendon system to adapt to progressively increasing eccentric muscle forces and the resultant structural and functional outcomes. Damage to the muscle-tendon is not an obligatory response. Rather, the muscle can hypertrophy and a change in the spring characteristics of muscle can enhance power; the tendon also adapts so as to tolerate higher tensions. Both basic and clinical findings are discussed. Specifically, we explore the nature of the structural changes and how these adaptations may help prevent musculoskeletal injury, improve sport performance, and overcome musculoskeletal impairments.

Efficacy of stairclimber versus cycle ergometry in postoperative anterior cruciate ligament rehabilitation

OBJECTIVE

To examine the effective use of stair climbing as an alternative to cycling for knee rehabilitation in an actual injured sport population.

DESIGN

Repeated-measures multivariate analyses with data collected during anterior cruciate ligament (ACL) rehabilitation.

SETTING

Clinical rehabilitation setting following ACL reconstruction.

PARTICIPANTS

46 athletes with ACL reconstruction (32 males, 14 females; age 25.5 +/- 8.9 yrs) were randomly assigned to either cycle or stairclimber programs previously matched by metabolic equivalents (METs) and heart rate.

MAIN OUTCOME MEASURES

Isokinetic testing was performed at 4 and 12 weeks postoperatively on the uninjured knee to safely determine mean and peak concentric quadriceps, eccentric quadriceps, concentric hamstring, and eccentric hamstring peak torques. Pre/post leg girths were also measured bilaterally (+7.6, +15.2, +22.9, -7.6, -15.2, -22.9 cm) proximal/distal to the patella.

RESULTS

Multivariate analysis of variance indicated no differences (Wilks' Lambda F(8,37) = 1.461; p = 0.21; eta(2) = 0.240; Power = 0.556) in strength gains (NM) between cycle and stair climbing groups, respectively, in mean concentric quadriceps (58.4 +/- 12.0 vs. 37.1 +/- 13.2), peak concentric quadriceps (77.0 +/- 14.7 vs. 36.8 +/- 16.2), mean eccentric quadriceps (57.2 +/- 12.7 vs. 79.2 +/- 14.0), peak eccentric quadriceps (78.6 +/- 19.3 vs. 105.5 +/- 21.3), mean concentric hamstring (14.3 +/- 3.9 vs. 6.5 +/- 4.3), peak concentric hamstring (24.0 +/- 6.7 vs. 22.2 +/- 7.4), mean eccentric hamstring (22.6 +/- 8.6 vs. 23.8 +/- 9.5), or peak eccentric hamstring (23.5 +/- 11.2 vs. 36.7 +/- 12.3) response. A significant stair climbing effect (Wilks' Lambda F(6,37) = 2.95; p = 0.02; eta(2) = 0.324; Power = 0.843) was observed in gastrocnemius girth (-15.2 cm) in both injured (0.5 +/- 0.1 cm vs. 0.3 +/- 0.1 cm, p < 0.04) and non-injured (0.3 +/- 0.1 cm vs. 0.0 +/- 0.1 cm, p < 0.008) legs.

CONCLUSIONS

In conclusion, the results of the data suggest no deleterious effect of stair climbing on knee isokinetic performance or limb girth measurements, and confirms the use of stair climbing as a viable adjunct/alternative to cycle ergometry in ACL-injured athletes.