Factors associated with the Single Leg Squat test in female soccer players: a cross-sectional study

BACKGROUND

The Single Leg Squat (SLS) test is widely used in the clinical setting to examine and evaluate rehabilitation goals. It is simple to perform and is proposed to have biomechanical and neuromuscular similarities to athletic movements. The aim of the present study was to investigate whether demographics, previous injuries, and biomechanical and psychosocial factors are associated with the outcome of the SLS, assessed as a total score for all segments and as a separate knee segment in elite and sub-elite female soccer players.

METHODS

We conducted a cross-sectional study involving 254 female soccer players (22 yrs; SD ± 4, height 1.69 m; SD ± 0.1, weight 64 kg; SD ± 6) from divisions 1-3 of the Swedish Soccer League. During the preseason, we assessed the participants using the SLS and tested their hip strength and ankle mobility. Demographics, previous injury, sleep quality, fear of movement, anxiety, and perceived stress were assessed with questionnaires. Logistic regression models were built to analyse the association between the outcome of the SLS and the independent variables for the dominant and non-dominant leg.

RESULTS

Significantly more participants failed the SLS on the dominant leg compared with the non-dominant leg (p < 0.001). The outcome of the SLS associated with various biopsychosocial factors depending on if the dominant or non-dominant leg was tested. The total score associated with hip strength for the dominant (OR 0.99, 95% CI 0.98-0.99, p = 0.04) and the non-dominant leg (OR 0.99, 95% CI 0.97-0.99, p = 0.03). The knee segment associated with division level for the dominant (div 2; OR 2.34, 95% CI 1.01-5.12, p = 0.033. div 3; OR 3.07, 95% CI 1.61-5.85, p = 0.001) and non-dominant leg (div 2; OR 3.30, 95% CI 1.33-8.00, p = 0.01. div 3; OR 3.05, 95% CI 1.44-6.43, p = 0.003).

CONCLUSIONS

This study identified that leg dominance, division level, hip strength, and psychosocial factors were associated with the outcome of the SLS when assessed as a total score and as a separate knee segment. This indicates that clinicians need to understand that movement control is associated with factors from several domains. Whether these factors and, the results of the SLS are related to injury need to be studied prospectively.

TRIAL REGISTRATION

Clinical Trials Gov, date of registration 2022-03-01.

CLINICAL TRIALS IDENTIFIER

NCT05289284A.

Reliability and validity of a novel Kinect-based software program for measuring a single leg squat

Background

The Single leg squat (SLS) is a movement screening test widely used in clinical settings. The SLS is highly subjective in its nature. Objective measures, such as 3D-motion analyses, are seldom used in daily clinical work. An interactive, Kinect-based 3D-movement analysis system, the Qinematic™, is proposed to be easily used in clinical settings to assess the SLS. The aim of this study was to establish the test-retest reliability and construct validity of Qinematic™ for assessing the SLS. A further aim was to identify angles of medial knee displacement, to summarise the discriminative ability of the SLS measured by Qinematic™.

Methods

We performed a test-retest reliability study (n = 37) of the SLS using Qinematic™ and a construct validity study, in which Qinematic™ data were compared with visual assessment of video-recorded SLS.

Results

Three variables (left knee down, right knee up and down) reached “substantial reliability” (ICC = 0.64–0.69). One variable, “left knee up”, showed a significant difference between the two test occasions (T1–6.34°, T2 0.66°, p = 0.013, ICC = 0.50), and “poor absolute reliability” was seen for all variables (SEM = 9.04–10.66, SDC = 25.06–29.55). A moderate agreement between the visual assessment and Qinematic™ data for various knee angles was shown (Kappa = 0.45–0.58). The best discriminative ability of the SLS was found at a knee angle of 6° (AUC = 0.82, sensitivity = 0.86, specificity = 0.78, PPV = 0.58, NPV = 0.94).

Conclusions

Qinematic™ shows a poor absolute reliability, and a substantial relative reliability, in measuring a SLS at the way down. This indicates that Qinematic™ should not be recommended for the use on an individual level, but it can possibly be used on a group level. The merged results of the construct validity study indicate that Qinematic™ at 6° of medial displacement can identify subjects with a knee over foot position. In summary, the use of the Qinematic™ net trajectory angle, which estimates the “line of best fit” cannot be recommended to assess a knee medial to foot position and should be reconsidered.

Visual assessment of movement quality in the single leg squat test: a review and meta-analysis of inter-rater and intrarater reliability

Single leg squat (SLS) is a common tool used in clinical examination to set and evaluate rehabilitation goals, but also to assess lower extremity function in active people.

Reliability and validity of a novel Kinect-based software program for measuring posture, balance and side-bending

Background

Clinical examinations are subjective and often show a low validity and reliability. Objective and highly reliable quantitative assessments are available in laboratory settings using 3D motion analysis, but these systems are too expensive to use for simple clinical examinations. Qinematic™ is an interactive movement analyses system based on the Kinect camera and is an easy-to-use clinical measurement system for assessing posture, balance and side-bending. The aim of the study was to test the test-retest the reliability and construct validity of Qinematic™ in a healthy population, and to calculate the minimal clinical differences for the variables of interest. A further aim was to identify the discriminative validity of Qinematic™ in people with low-back pain (LBP).

Methods

We performed a test-retest reliability study (n = 37) with around 1 week between the occasions, a construct validity study (n = 30) in which Qinematic™ was tested against a 3D motion capture system, and a discriminative validity study, in which a group of people with LBP (n = 20) was compared to healthy controls (n = 17). We tested a large range of psychometric properties of 18 variables in three sections: posture (head and pelvic position, weight distribution), balance (sway area and velocity in single- and double-leg stance), and side-bending.

Results

The majority of the variables in the posture and balance sections, showed poor/fair reliability (ICC < 0.4) and poor/fair validity (Spearman <0.4), with significant differences between occasions, between Qinematic™ and the 3D–motion capture system. In the clinical study, Qinematic™ did not differ between people with LPB and healthy for these variables. For one variable, side-bending to the left, there was excellent reliability (ICC =0.898), excellent validity (r = 0.943), and Qinematic™ could differentiate between LPB and healthy individuals (p = 0.012).

Conclusion

This paper shows that a novel software program (Qinematic™) based on the Kinect camera for measuring balance, posture and side-bending has poor psychometric properties, indicating that the variables on balance and posture should not be used for monitoring individual changes over time or in research. Future research on the dynamic tasks of Qinematic™ is warranted.