Number of Repetitions to Maximum in Hop Tests in Patients with Anterior Cruciate Ligament Injury

Limb Symmetry Index of Single-Leg Vertical Jump vs. Single-Leg Hop for Distance After ACL Reconstruction: A Systematic Review and Meta-analysis

CONTEXT

The limb symmetry index (LSI) is recommended as a milestone of return to play (RTP), and relying on the LSI value of a single-leg hop for distance (SLHD) test may overestimate rehabilitation status. Identifying a more reliable functional test can help to carefully make decisions for RTP.

OBJECTIVE

The aim was to compare the LSI value of the SLHD test with that of a single-leg vertical jump (SLVJ) test after anterior cruciate ligament reconstruction (ACLR) and determine which test provides lower LSI values.

DATA SOURCES

The PubMed, Web of Science, Embase, and Cochrane Library databases were searched from inception to July 2022.

STUDY SELECTION

Observational studies with participants who had both SLHD and SLVJ tests after ACLR and LSI values of an SLHD and SLVJ were included. Disagreements were resolved after discussion between the 2 researchers.

STUDY DESIGN

Systematic review and meta-analysis.

LEVEL OF EVIDENCE

Level 4.

DATA EXTRACTION

Data on the primary outcomes (LSI values of the SLVJ and SLHD tests) were collected. Means and standard deviations (SDs) for each variable of interest were used to calculate standardized mean differences (SMDs).

RESULTS

A total of 12 studies met the inclusion criteria for the meta-analysis. A total of 587 patients underwent SLHD and SLVJ tests at different time points after ACLR. Compared with the SLHD test, the SLVJ test provided lower LSI values (SMD -0.42; 95% confidence interval (CI) -0.67 to -0.17). Subgroup analysis found that the SLVJ test provided a lower LSI value than the SLHD test in a specific period (approximately 7-18 months after ACLR, SMD -0.53; 95% CI -0.91 to -0.14) and a similar LSI value at other times.

CONCLUSION

The SLVJ test provided lower LSI values in a specific period (7-18 months after ACLR).

The effect of knee extensor open kinetic chain resistance training in the ACL-injured knee

PURPOSE

To investigate the effect of different loads of knee extensor open kinetic chain resistance training on anterior knee laxity and function in the ACL-injured (ACLI) knee.

METHODS

Fifty-eight ACLI subjects were randomised to one of three (12-week duration) training groups. The STAND group trained according to a standardised rehabilitation protocol. Subjects in the LOW and HIGH group trained as did the STAND group but with the addition of seated knee extensor open kinetic chain resistance training at loads of 2 sets of 20 repetition maximum (RM) and 20 sets of 2RM, respectively. Anterior knee laxity and measurements of physical and subjective function were performed at baseline, 6 and 12 weeks. Thirty-six subjects were tested at both baseline and 12 weeks (STAND n = 13, LOW n = 11, HIGH n = 12).

RESULTS

The LOW group demonstrated a reduction in 133 N anterior knee laxity between baseline and 12 weeks testing when compared to the HIGH and the STAND groups (p = 0.009). Specifically, the trained-untrained knee laxity decreased an average of approximately 5 mm in the LOW group while remaining the same in the other two groups.

CONCLUSION

Twelve weeks of knee extensor open kinetic chain resistance training at loads of 2 sets of 20RM led to a reduction in anterior knee laxity in the ACLI knee. This reduction in laxity does not appear to offer any significant short-term functional advantages when compared to a standard rehabilitation protocol. These results indicate that knee laxity can be decreased with resistance training of the thigh muscles.

LEVEL OF EVIDENCE

Randomised controlled trial, Level II.

Are practice trials required for hop tests?

Single-legged hop tests are commonly used in clinic and research settings to obtain information on functional performance of the injured leg. When performing these tests, it is typical to provide a few practice trials before performing actual test trials. However, the importance of practice trials and how it affects performance during actual test trials are not known. This study investigated the effect of practice trials on single-leg hop performance using a marker-based kinematic tracking approach in individuals with anterior cruciate ligament (ACL) reconstruction and athletic controls. Thirteen subjects with ACL reconstruction and thirteen uninjured healthy subjects performed the single hop for distance test for both legs. Three practice and five test trials were performed on each leg. Single-leg hop distance scores and hop indices (i.e., side-to-side hop distance ratios) obtained from practice and test trials were compared. There were significant differences in the mean hop distance between practice and test trials (P<0.05) when raw scores were compared, but no differences were observed when comparing the side-to-side distance ratios (P>0.05). There were also significantly high correlations between practice and test trials (P<0.01) and the agreement between practice and test scores was very good (ρc=0.88-0.98). The findings suggest that subjects indeed improve their performance during test trials; however, the improvements had an inconsequential effect on the side-to-side hop distance ratios. Therefore, if the examiner is interested only in side-to-side ratios, then practice trials can be minimized or even avoided to improve efficiency and minimize time and costs associated with additional trials.

Distance reached in the Anteromedial Reach Test as a function of learning and leg length

The anteromedial reach test (ART) is a new outcome measure for assessing dynamic knee stability in anterior cruciate ligament-injured patients. The effect of learning and leg length on distance reached in the ART was examined. Thirty-two healthy volunteers performed 15 trials of the ART on each leg. There was a moderate correlation (r = .44-.50) between reach distance and leg length, therefore reach distances were normalized for leg length. Normalized reach distance increased significantly over the 15 trials (p < .01), reaching a plateau after 8 trials, identified by a moving average graph. It is recommended that participants be afforded eight practice trials and that reach distances be normalized by expressing them as a percentage of leg length.

The ability of 4 single-limb hopping tests to detect functional performance deficits in individuals with functional ankle instability

STUDY DESIGN

Experimental laboratory testing using a cross-sectional design.

OBJECTIVES

To determine if functional performance deficits are present in individuals with functional ankle instability (FAI) in 4 single-limb hopping tests, including figure-of-8 hop, side hop, 6-meter crossover hop, and square hop.

BACKGROUND

Conflicting results exist regarding the presence of functional deficits in individuals with FAI. It is important to evaluate whether functional performance deficits are present in this population, as well as if subjective feelings of giving way can assist in identifying these deficits.

METHODS

Sixty college students volunteered for this study. Thirty participants with unilateral ankle instability were placed in the FAI group and 30 participants with no history of ankle injuries were placed in the control group. The FAI group was subsequently further divided to indicate those that reported giving way during the functional test (FAI-GW) and those that did not (FAI-NGW). Time to complete each test was recorded and the mean of 3 trials for each test were used for statistical analysis. To identify performance differences, we used 4 mixed-design 2-way (side-by-group) ANOVAs, 1 for each hop test. A Tukey post hoc test was completed on all significant findings.

RESULTS

We identified a significant side-by-group interaction for all 4 functional performance tests (P<.05). Specifically, for each functional performance test, the FAI limb performed significantly worse than the contralateral uninjured limb in the FAI-GW group. Additionally, the FAI limb in the FAI-GW group performed worse than the FAI limb in the FAI-NGW group, and the matched limb in the control group in 3 of the 4 functional performance tests.

CONCLUSION

We found that functional performance deficits were present in participants with FAI who also experienced instability during the test. This difference was identified when comparing the FAI limb to the contralateral uninjured limb as well as control participants. However, the performance deficits identified in this study were relatively small. Future research in this area is needed to further evaluate the clinical meaningfulness of these findings. Finally, we found that limb dominance did not affect performance.

Comparison of conventional resistance training and the fly-wheel ergometer for training the quadriceps muscle group in patients with unilateral knee injury

A fly-wheel ergometer (FWE) offering resistance training of the knee extensors has been designed for space travel and found to be effective during bed rest. The possibility exists that this device is also effective in training the knee extensors after knee injury. The purpose of this study was to compare the FWE to standard knee extensor training equipment for their effects on individuals with a history of knee injury, a group who commonly suffer from weakness of the knee extensors that effects their function. Twenty-nine subjects completed the study, which included tests of knee self-assessment, knee extensor static and dynamic muscle strength, size and neural activation as well as single leg power output, standing balance and vertical jump performance. Both groups showed statistically significant (P < 0.05) improvements in these variables over the 3-month training period but no differences were noted between the groups. The FWE appears to be as effective as standard resistance training equipment for improving knee extensor muscle group size and performance after knee injury.