The relationship between y balance performance and hip strength in recreationally trained women

This study set one ́s sight on the relationship between lower quarter y balance test (YBT-LQ) score with hip isometric strength with recreationally resistance-trained women. Utilizing dynamic balance as a screening tool for lower extremity injury risk has been proposed as a potential solution in injury prevention and injury assessment. A convenience sample of twenty young college females (22.3 ± 2.1 years) with a background in regular strength or plyometric training volunteered to participate in this study. The scores of YBT-LQ for each direction were calculated. A hand-held dynamometer was used to measure the maximum voluntary isometric strength of each participant ́s unilateral hip extensors, flexors, adductors, abductors, internal and external rotation muscles. Significant lower normalized score was noted for the dominant limb (81.2 ± 11.7) when compared to non-dominant limb (83.6 ± 12.4) for anterior distance. For the composite score of YBT-LQ, a weak association was noted for hip extension and internal rotation, and moderate association was observed for hip flexion, adduction, and abduction. On the other hand, a strong association was observed between hip external rotators strength (r =0.516). Thus, the main finding of the current study was the strong association observed between hip external rotators strength and composite score of YBT-LQ.


Introduction
Dynamic balance is an integral component when examining lower extremity injury risk considering that the neuromuscular system has an important role n dynamic stability (Riemann & Lephart, 2002). Utilizing dynamic balance as a screening tool for lower extremity injuries has been proposed as a potential solution in injury avoidance and injury assessment (Brech, et al., 2013). Hip abductor and external rotator muscle strength play a major role in reducing knee adduction and internal rotation torque (Kendall, et al., 2005). Specifically, hip abductor and external rotator muscle strength deficits are associated with the femoral position of adduction and internal rotation torque at the knee (dynamic knee valgus) and consequently affect hip dynamic balance (Gordon, et al., 2013).
An increasing number of studies have attempted to identify variables related to dynamic balance, static balance, and ankle range of motion (ROM) aiming to predict lower extremity injuries in physically active populations (Paz, et al., 2016, Williams, et al., 2016. One instrument utilized to examine dynamic balance is the Lower Quarter Y Balance Test (YBT-LQ).
The YBT-LQ is a platform apparatus variant of the Star Excursion Balance Test (SEBT), employing three of the original eight reaching directions: anterior, posteromedial and posterolateral (Wilson, et al., 2018). This dynamic balance instrument incorporates standardized height, stance foot placement and reaching measurements. The YBT-LQ has been verified as a reliable test with a high proficiency of inter and intra-rater reliability (McCann, et al., 2017). The benefits of the YBT are that it has a standard protocol and high inter-rater (0.99-1.00) and intra-rater (0.85-0.91) reliabilities (Linek, et al., 2017). Wilson et al. (2018) examined the relationship between elements of isometric hip strength and the Y Balance Test, to provide clinicians better guidance as to specific areas of muscle performance to address in the event of poor performance on the Y Balance Test. The authors found significant positive correlations between Y-Balance Test performance and hip abduction strength. They also found correlations between the Y-Balance Test and hip extension and external rotation strengths. Hartley et al. (2018) investigated static balance, dynamic balance, ankle range of motion, body mass index (BMI), or history of an ankle sprain were all associated with ankle sprain injuries within collegiate athletes of both sexes. Research, Society andDevelopment, v. 10, n. 10, e327101019167, 2021 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v10i10.19167 3 They noticed that male collegiate athletes with greater BMI and lesser YBT-LQ anterior reach were at a greater risk of sustaining an ankle sprain injury.
Understanding the dynamic balance framework for each particular population allows for specific standard performance evaluation points to be established. Although the authors understand that the relationship between dynamic balance and isometric strength is already established, we consider it relevant to address this topic exclusively to recreationally.
Thus, this evidence may help conditioning professionals and practitioners during the training prescription and assessment.
Therefore, the purpose of this study was to identify the relationship between YBT-LQ score with hip isometric strength with recreationally resistance trained college women 2. Methodology

Experimental design
This was an experimental qualitative research whose sample was selected for convenience (Medronho, et al., 2009).

Participants
Twenty young college females with background in regular strength or plyometric training volunteered to participate in this study (Age 22.3± 2.1; Height 161.1± 5.3 (cm); mass 65.2± 3.9 (kg)). Power analysis was conducted to determine sample size (n) using Cohen's d (Cohen, 2013) of ~1.1-1.3 for improvements in muscular performance. Sample size was calculated revealing that each group required between 13 and 15 participants to meet the required power of 0.8 at an alpha value of p<0.05. All participants had at least three years of resistance training experience (3.5 ± 1.2 years), averaging 60-min per sessions three times a week. All participants were active in competitive sports training or were active in actual competition one to four times per week. The exclusion criteria adopted for the current research was: (a) potential medical problems such as joint injuries or a history of ankle, knee or back pathology that compromised their participation or performance during the proposed tests; (b) any lower extremity surgery in the prior two years.

Protocol
Participants indicated their "dominant limb" by answering which leg they would use to kick a ball. Limb testing was randomized. Prior to data collection, the participants were informed about the experimental procedures and about possible risks and benefits associated with their participation in the study and signed an informed consent before any of the tests performed.
Procedures were approved by the Institutional Ethics Review Committee of the University in accordance with the current national and international laws and regulations governing the use of human subjects (Declaration of Helsinki II).
Y balance test (YBT-LQ) measurement: Participants completed the YBT-LQ using a metric tape fixed on the floor in a manner previously described in the literature (Ganesh, et al.,2015;Gordon, et al., 2013;Johnston, et al., 2018). The participants stood with one leg -the stance leg-on the starting position, and used their opposite leg, the reaching leg, to touch as far as possible with the halux in the anterior, posterolateral, and posteromedial directions sustaining the farthest reach for at least two seconds. Attempts did not count if the participant was unable to maintain a single leg stance throughout the entire movement, rested the left foot out of the mark while reaching, elevated the suporting ankle in an attempt to gain extra distance, or the participant did not return to starting position with maintained balance. Each participant completed three testing trials in each direction with each leg after completing six practicing trials, which were included to familiarize the participant with the testing maneuvers. One-minute rest between repetitions was adopted to prevent fatigue. Only values from the three testing trials were used to calculate the subject's scores.
Scores for each direction (anterior, posteromedial, and posterolateral) were calculated by dividing the average reach distance (in cm) by the participant's leg length (in cm) and multiplying by 100 (Paz, et al., 2017). The patient's leg length was measured from the most prominent aspect of the anterior-superior iliac spine to the distal tip of the ipsilateral medial malleolus. To calculate the composite score, the sum of maximum reaches in each directions was divided by three times the leg length (Paz, et al., 2017).
Handheld dynamometer: A MicroFet 2 hand-held dynamometer (Hogan Health Industries, Inc. 8020 South 1300 West, West Jordan, USA) was used to measure the maximum voluntary contraction. The rater was a physical education professional with five years of experience in testing procedures. The maximal isometric contraction of the unilateral hip extensors, flexors, adductors, abductors, internal and external rotation was adopted following procedures suggested by Kendall et al (2005). Participants were told to stop contracting when the tester finished counting to five seconds (Williams, et al., 2016). This duration was shown to be adequate for most subjects in order to reach the maximum force (Douma, et al., 2014). The mean peak value of these three trials for each muscle group was used for the data analysis.

Statistical Analysis
All statistical analysis were performed using SPSS 23 Statistics Software (SPSS Inc. Chicago, IL). Data were tested for normality using the Shapiro-Wilk test. Mean and standard deviations were calculated for each of the variables, on each leg.
T-tests were performed to determine if there were any between limb differences of the dominant and non-dominant leg.
Pearson correlation coefficients were calculated between the three hip strength measurements and the Y-Balance test scores.
To describe the strength of the correlation, the following scale was used for the absolute value of the correlation coefficient (r): strong relationship (0.50 ≤ r ≤ 1.0), moderate relationship (0.3≤ r < 0.5), and weak relationship (r < 0.3) (Hopkins, et al., 2009).
The level of significance for all analysis was set at p ≤ 0.05.

Results and Discussion
No difference between dominant and non-dominant limb was noted for posterolateral and posteromedial parameters of YBT-LQ (Table 1 provided for observation). However, a significant lower score was noted for dominant limb when compared with the non-dominant limb for anterior distance. No difference between limbs was observed for all hip strength evaluation applied in the present study. Research, Society and Development, v. 10, n. 10, e327101019167, 2021 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v10i10.19167 5 A weak association was noticed between hip extension, internal rotators and anterior distance of YBT-LQ test (Table   2 provided for observatiob). On the other hand, moderate association was observed between hip extension, adduction, abduction and external rotation with anterior reach distance. For posterolateral reach distance, a weak association was noted for hip flexion, extension, adduction and abduction (Table 3 provided for observation). However, moderate association was observed for internal and external rotators.  For posteromedial reach distance, a weak association was noted for hip flexion, extension, abduction and internal rotation (Table 4 provided for observation). However, moderate association was noted for hip adduction and external rotation.
For composite score of YBT-LQ, a weak association was noted for hip extension and internal rotation (Table 5 provided    The purpose of this study was to identify the relationship between YBT-LQ score and hip isometric strength in recreationally resistance trained women. The main finding of the current study was the strong association observed between hip external rotators strength and composite score of YBT-LQ. A weak/moderate association was noted between hip flexion, extension, adduction, abduction and internal rotation isometric strength and YBT-LQ reach distances or composite score. These results were partially in agreement with the previous evidences observed in the scientific literature (Brech, et al., 2013;Chen & Chou, 2017;Culiver, et al., 2019;Linek, et al., 2017;McCann, et al., 2017).
Despite the lack of a significant difference, a strong association between hip external rotation strength and the composite score of YBT-LQ was found in the present study. On the other hand, Gordon et al (2013)  14.5 ± 4.9 N). In the present study, the participants has at least three years of regularly resistance training experience, different to Wilson et al (18) who evaluated participants classified as moderately active in recreational activities.
The relevance of the participants background can be noted in Lee et al (2014) study, which investigated the relationship between YBT-LQ distance and the lower-limb strength of adult women aged 45 to 80 years. Participants were tested for maximal muscle strength of the lower limbs (hip extensors, hip flexors, hip abductors, knee extensors, knee flexors, and ankle dorsiflexors) and YBT-LQ distances in the anterior, posteromedial, and posterolateral directions. The authors noted a weak correlation between lower-limb strength (hip extensors, hip abductors, and knee flexors) and dynamic postural control as measured by the YBT-LQ. In another study Lee et al (2015) investigated the ability of the YBT-LQ and lower limb strength to discriminate between females in two age groups, the relationship between YBT-LQ distance and the Berg Balance Scale (BBS), and the degree to which performance on YBT-LQ distance is related to lower limb strength in middle-aged and older females. The YBT-LQ distance in three directions and lower limb muscle strength for both lower limbs were significantly lower in the older adults than in the middle-aged group. A moderate correlation but insignificant correlation was found between the YBT-LQ composite and the BBS scores. In the older females, YBT-LQ distance was significantly positively correlated with strength of the knee flexor and hip abductor. In the middle-aged group, YBT-LQ distance was significantly positively correlated with strength of the knee flexor and hip extensor. This collection of evidence shows controversial results.
It´s important to highlight that the intervention was proposed using a modified version of the YBT-LQ using a fixed tape on the floor which can lead the individuals to different neuromuscular strategies in order to maintain their balace. For instance, Jagger et al (2020)

Final Considerations
There are important limitations in this study. First, we only tested healthy females with resistance training background. The healthy participants in the study conducted by Lee et al (2015) had an average age of 65.73 years, while the moderate physically active participants in the study by Wilson et al (18) had an average age of 25.40 year s in the healthy participants in this study. This suggests that the age of the participant could play a larger role than their injury status and explain the discrepancy seen between correlations amongst the studies. However, the use of healthy subjects decreased the possibility that lower extremity pathology such as patellofemoral pain, ankle instability, or other limitations would prevent maximal performance.
Furthermore, the present findings provide clinicians with useful information regarding the relative contribution of hip muscle strength to YBT-LQ performance when evaluating dynamic balance in resistance training field. Further studies are needed to determine the clinical utility of this test in different age groups or injury conditions. All things considered, the main finding of the current research was the strong association observed between hip external rotators strength and composite score of YBT-LQ. A weak or moderate association was noted between hip flexion, extension, adduction, abduction and internal rotation isometric strength and YBT-LQ reach distances or composite score.