Evaluation of Lower Limb Asymmetry Index Based on the 30-Second Skater Squat Functional Test in Young Men

Introduction: Physical performance tests (PPTs) are used for the pre-season evaluation of athletes and to monitor and control the rehabilitation process. PPTs include single-leg jumps, single-leg squats, and balance tests. One of the physical fitness tests is the skater squat test. The 30 s skater squat functional test (SSFT) is used as one of the tests to assess fitness and symmetry in the lower limbs. The present study aimed to calculate and compare the asymmetry index using the 30 s skater squat functional test, the single-leg distance jump test, and the isometric measurement of knee joint extensor strength. Materials and Methods: The study examined 25 men aged 23 ± 3.17 years. The study used the 30 s SSFT, the single-leg long jump test (SLLJT), and an isometric dynamometer test to measure peak moment of force values for extensors of the knee using the JBA Zbigniew Staniak® measuring station ("JBA" Zb. Staniak, Poland). The statistical analysis of functional test results and iso-metric dynamometry results was based on correlation analysis. Results: There was a moderate correlation between 30 s SSFT and SLLJT (r = 0.540), and between SLLJT and measurements of peak moment of force of the knee joint extensors (r = 0.533). Conclusions: The asymmetry index calculated based on functional tests and peak moment of force of the knee extensors in a group of young men should not be used interchangeably. The asymmetry index calculated from the 30 s skater squat functional test detects greater differences in knee extensor strength than the ASI index calculated from the single-leg long jump test in a group of young male athletes. The practical significance of this study was that its results could play an important role in the training process and monitoring the return to sports after a possible injury.

Recurrence quantification analysis of isokinetic strength tests: A comparison of the anterior cruciate ligament reconstructed and the uninjured limb

BACKGROUND

Despite widespread use of return to sport testing following anterior cruciate ligament reconstruction, studies suggest inadequacy in current testing criteria, such as limb symmetry index calculations, to determine athletes' readiness to return to play. Recurrence quantification analysis, an emerging non-linear data analysis tool, may reveal subtle neuromuscular differences between the injured and uninjured limb that are not captured by traditional testing. We hypothesized that isokinetic torque curve data of the injured limb would demonstrate lower determinism and entropy as compared to the uninjured limb.

METHODS

102 patients (44 M, 58F, 10 ± 1 months post-anterior cruciate ligament reconstruction) underwent isokinetic quadriceps strength testing using a HumacNorm dynamometer. Patients completed maximum effort knee extension and flexion at 60°/sec. Data were post-processed with a MATLAB CRQA Graphical User Interface and determinism and entropy values were extracted. Paired-sample t-tests (α = 0.05) were used to compare data from the injured and uninjured limb.

FINDINGS

Determinism and entropy values in the torque curves were lower in the injured limb than the uninjured limb (p < 0.001). Our findings indicate there is less predictability and complexity present in the torque signals of injured limbs.

INTERPRETATION

Recurrence quantification analysis can be used to assess neuromuscular differences between limbs in patients who have undergone anterior cruciate ligament reconstruction. Our findings offer further evidence that there are changes to the neuromuscular system which persist following reconstruction. Further investigation is needed to establish thresholds of determinism and entropy values needed for safe return to sport and to evaluate the utility of recurrence quantification analysis as a return to sport criterion.

Knee extensor strength, hop performance, patient-reported outcome and inter-test correlation in patients 9-12 months after anterior cruciate ligament reconstruction

BACKGROUND

Hop performance and isokinetic knee extensor strength (IKES) asymmetry are associated with re-injury after anterior cruciate ligament reconstruction (ACLR). This study investigated deficits after ACLR, and which hop tests are most correlated with IKES and patient-reported outcome measures (PROMs).

METHODS

50 patients were assessed 9-12 months after ACLR using the International Knee Documentation Committee (IKDC) and ACL Return to Sport after Injury (ACL-RSI) scores. Peak IKES and eight hop tests were assessed: single (SHD), triple (THD) and triple crossover (TCHD) hop for distance, 6 m timed hop (6MTH), single medial (MHD) and single lateral (LHD) hop for distance, single countermovement jump (SLCMJ) and timed speedy hop (SHT). The percentage of patients with limb symmetry indices (LSIs) < 90% was reported. Pearson's correlations investigated the correlation between PROMs, IKES and hop LSIs.

RESULTS

The majority (80%) of patients had IKES LSIs < 90%. While 12-14% of patients demonstrated LSIs < 90% for the SHD, 6MTH, THD and TCHD, 52-80% demonstrated LSIs < 90% for the other hop tests. The IKES LSI was significantly different (p < 0.05) from all hop LSIs, besides the SLCMJ (p = 0.638). Large correlations were only observed between the IKES LSI and the SLCMJ (r = 0.82), MHD (r = 0.71) and LHD (r = 0.53). The SLCMJ, MHD and IKES LSIs demonstrated the largest significant correlations with the IKDC (r = 0.51-0.53) and ACL-RSI (r = 0.38-0.40).

CONCLUSIONS

Hop tests such as the MHD and SLCMJ may present a more practical alternative to quantifying peak IKES, especially in the absence of more sophisticated testing equipment. While not surrogates as such, these selective hop measures may better inform the clinician as to whether significant underlying quadriceps deficits are still present throughout the post-operative rehabilitation period.

Who Passes Return-to-Sport Tests, and Which Tests Are Most Strongly Associated With Return to Play After Anterior Cruciate Ligament Reconstruction?

Background:

Return-to-sport (RTS) testing after anterior cruciate ligament (ACL) reconstruction (ACLR) surgery has become popular. It has been recommended that such testing should incorporate several domains, or set of tests, but it is unclear which are most associated with a successful RTS.

Purpose:

To determine (1) the proportion of patients who can pass a set of self-report and functional tests at 6 months after ACLR; (2) age, sex, and activity level differences between patients who pass and those who do not; and (3) whether specific types of tests are associated with a return to competitive sport at 12 months.

Study Design:

Cohort study; Level of evidence, 2.

Methods:

This was a prospective longitudinal study of 450 patients who had primary ACLR. At 6 months postoperatively, patients completed 2 self-report measures, the International Knee Documentation Committee (IKDC) subjective knee form and ACL–Return to Sport after Injury (ACL-RSI) scale, and 3 functional measures: single hop and triple crossover hop for distance and isokinetic quadriceps strength. Limb symmetry index scores of ≥90 for functional tests, IKDC scores ≥85, and ACL-RSI scores ≥65 were considered indicators of satisfactory recovery. Proportional statistics and contingency analysis were used to determine associations between age, sex, preinjury sports level, and (1) meeting test thresholds and (2) RTS at 12 months.

Results:

Only 17 (3.8%) patients met all 5 test criteria at 6 months, and 95 (21%) patients did not pass any test. More of the younger patients (<21 years) passed all of the functional tests (P < .01), and more male patients met the IKDC threshold (P = .03). Patients who played level I sports before injury had the same pass rates as those who played level II/III sports. Patients who passed the thresholds for the ACL-RSI and IKDC scales had 4 and 3 times the odds, respectively, of RTS at 12 months (both P < .0001). Meeting the threshold for quadriceps strength or either of the hop tests at 6 months was not associated with RTS.

Conclusion:

At 6 months after ACLR, few patients met all of the thresholds of the common tests used to assess RTS ability, although younger patients had higher rates of passing the functional tests. Self-perceived symptoms/function and psychological readiness were associated with a return at 12 months.