The back squat: A proposed assessment of functional deficits and technical factors that limit performance

Using Isometric Squat Strength to Predict Concentric and Eccentric Squat Strength in Young and Older Adults

BACKGROUND

Resistive squat exercise is a well-established technique to enhance the strength of muscles and bones of the back extensors in humans. Rehabilitation programs aimed at strengthening the muscles and bone of the back require the knowledge of the patient's 1 repetition maximum (RM) of squat exercise. Finding the 1RM value of squat exercise could lead to injury or seem nonfeasible because of the higher weights involved, especially in older adults.

PURPOSE

To investigate the predictive relationship between the maximum voluntary isometric squat strength and the 1RM concentric and eccentric squat strength in young and older individuals.

METHODS

In our cross-sectional study, individuals from two age populations, 21-35 years (young) and 55-75 years (older) were recruited and participated in two visits within a two-week period. Our main outcome measures were: Maximum voluntary isometric squat strength (IsoMax) and 1RM of concentric (ConMax) and eccentric (EccMax) back squat strength were calculated for young and older adults. All the strength measures were normalized for body weight.

RESULTS

IsoMax was a significant predictor of the ConMax (p = 0.003; Normalized ConMax = 0.708 + 1.376(Normalized IsoMax); 95%CI: 0.583-2.169) and EccMax (p = 0.003, Normalized EccMax = 0.844 + 1.433(Normalized IsoMax); 95%CI = 0.582-2.284) in older adults only. There was a trend toward significance for the relationship between IsoMax and ConMax (p = 0.058) in young adults.

DISCUSSION

Our novel findings show that safe techniques for muscle strength assessment, such as maximum voluntary isometric squat strength, can be utilized in older populations to predict their 1RM of concentric and eccentric squat strength. Our novel equations provide the information necessary for designing effective rehabilitation regimes for strengthening the muscles and bone of the back in older adults.

Using 30-s Prone Back Extension Repetition Maximum Test to Predict Concentric and Eccentric 1 Repetition Maximum Squat Strength in Young and Older Adults

Background: One repetition maximum (1RM) testing depends on lifting heavy loads which can put older adults at risk for injury and thus is nonfeasible. Thus, there is a great need for alternative 1RM testing methods, which are safe, patient-friendly, and clinically applicable, in older adults. Notably, aging-induced loss of muscle strength is greater for concentric than eccentric strength. However, there is a lack of information on unique 1RM for concentric and eccentric squat strength. Such information can lay the framework to design novel and effective resistive squat exercise programs in line with the principles of precision rehabilitation for various clinical populations. Purpose: To investigate if the 30-s prone back extension repetition maximum test can predict 1RM concentric and eccentric squat strength in young and older individuals. Methods: We enrolled and tested participants from 2 age groups: young: 21-35 years and older: 55-75 years in our cross-sectional study. Our main outcome measures were 30-s prone back extension repetition maximum and 1RM of concentric and eccentric back squat strength. All strength measures were normalized for body weight. Results: Thirty-second prone back extension repetition maximum significantly predicted 1RM concentric (p=0.030, ß = 0.56; 95% CI: 0.006-0.102) and 1RM eccentric squat strength (p=0.041; β = 0.030, 95% CI: 0.001-0.058) in young and older adults, respectively. In addition, we obtained a trend toward significance for the relationship between 30-s prone back extension repetition maximum and 1RM eccentric (p=0.078) and 1RM concentric (p=0.066) squat strength in young and older adults, respectively. Discussion: Novel data from our study show that 30-s prone back extension repetition maximum can predict 1RM of concentric and eccentric squat strength in young and older adults, respectively. Thus, clinicians and rehabilitation professionals can use our novel equations to design concentric- and eccentric-biased resistive training programs in young and older adults, respectively, without testing for 1RM.

The Development and Content of Movement Quality Assessments in Athletic Populations: A Systematic Review and Multilevel Meta-Analysis

BACKGROUND

Despite their prominence in the sport and human movement sciences, to date, there is no systematic insight about the development and content of movement quality assessments in athletic populations. This is an important gap to address, as it could yield both practical and scientific implications related to the continued screening of movement quality in athletic contexts. Hence, this study aimed to systematically review the (i) developmental approach, (ii) movements included, (iii) scoring system utilised, and (iv) the reliability of movement competency assessments used in athletic populations.

METHODS

Electronic databases (SPORTDiscus, MEDLINE, CINAHL, Web of Science, Scopus) were searched for relevant articles up to 12 May 2023. Studies were included if they reported data about the developmental approach, movements included, scoring system utilised and reliability of assessment in an athletic population. A modified Downs and Black checklist was used to measure study quality.

RESULTS

From a total of 131 identified studies: (i) 26 (20%) described the developmental approach of an assessment; (ii) 113 (86%) included descriptions of the movements included; (iii) 106 (81%) included a description of scoring system and criteria; and (iv) 77 (59%) studies included reliability statistics. There were 36 assessments identified within these studies, comprising 59 movements in total. Each assessment scored movement quality through a Likert or binary classification system.

CONCLUSION

First, the results demonstrate that choosing an appropriate movement quality assessment in an athletic population may be a complex process for practitioners as the development approach, movements included and scoring criteria vary substantially between assessments. Second, academics could use these results to help design new assessments for novel applications that meet rigour and reliability requirements. Third, these results have the potential to foster guidelines of use for the reliable assessment of movement quality in athletic populations.

Identifying the Primary Kinetic Factors Influencing the Anterior-Posterior Center of Mass Displacement in Barbell Squats: A Factor Regression Analysis

BACKGROUND

Barbell squats are commonly used in strength training, but the anterior-posterior displacement of the Center of Mass (COM) may impair joint stability and increase injury risk. This study investigates the key factors influencing COM displacement during different squat modes.; Methods: This study recruited 15 male strength training enthusiasts, who performed 60% of their one-repetition maximum (1RM) in the Front Barbell Squat (FBS), High Bar Back Squat (HBBS), and Low Bar Back Squat (LBBS). Joint moments at both the hip, knee, and ankle were collected using a motion capture system and force plates, and a factor regression analysis was conducted using SPSS.; Results: In the FBS, primary factors influencing COM displacement included right knee adduction-abduction (38.59%), knee flexion-extension (31.08%), and hip internal-external rotation (29.83%). In the HBBS, they were right ankle internal-external rotation (19.13%), hip flexion-extension (-19.07%), and left knee flexion-extension (19.05%). In the LBBS, the key factors were left knee adduction-abduction (27.82%), right ankle internal-external rotation (27.59%), and left ankle internal-external rotation (26.12%).; Conclusion: The study identifies key factors affecting COM displacement across squat modes, with knee flexion-extension being dominant in the FBS and hip moments more significant in the HBBS and LBBS. These findings have implications for optimizing squat training and injury prevention strategies.

Clinical presentation of anterior pelvic tilt and trunk muscle endurance among patients with femoroacetabular impingement syndrome: a cross-sectional study

BACKGROUND

Femoroacetabular impingement syndrome (FAIS) significantly affects the physical function and quality of life of the young and middle-aged population. Pelvic tilt and trunk muscle endurance are physical features poorly studied in FAIS.

AIM

This study aimed to compare the anterior pelvic tilt and anterior, lateral, and posterior trunk muscles endurance between people with FAIS and healthy individuals, within FAIS sub types and between the symptomatic and asymptomatic hip in people with FAIS.

DESIGN

Cross-sectional study.

SETTINGS

Participants were recruited and screened for potential eligibility at the Rehabilitation, Sports Medicine, and Physiotherapy Unit between April 2021 and February 2022.

POPULATION

Sixty-nine patients with FAIS and 69 controls.

METHODS

A study adhering to STROBE guidelines recruited 138 participants (69 FAIS, 69 controls). The degree of pelvic tilt was measured by the palpation meter (PALM) tool. To assess trunk musculature endurance, isometric trunk tests described by McGill were performed (extension resistance test, flexion resistance test, and side plank test). Cases were classified based on FAIS subtypes. Differences between groups and subgroups were performed using t-tests and ANCOVA, respectively.

RESULTS

Significant differences in anterior pelvic tilt were observed between the control and FAIS groups (P<0.001, d=0.72). Participants with FAIS exhibited greater pelvic tilt (MD=1.57, 95% CI=0.83 to 2.3). Trunk muscle endurance showed statistically significant differences (P<0.001, d=0.72) for posterior muscles. In comparisons between symptomatic and asymptomatic hips, significant differences were found in pelvic tilt (P<0.001, d=0.26) and lateral trunk muscle endurance (P<0.001, d=0.43). FAIS subtypes demonstrated significant differences in lateral trunk muscle endurance (P=0.002, ηp2=0.209).

CONCLUSIONS

This study found that patients with FAIS present large anterior pelvic tilt and lower posterior trunk muscle endurance. Although anterior pelvic tilt was comparable for all FAIS subtypes, Pincer-type with or without labral tear exhibited lower lateral trunk muscle endurance compared with Cam-type with or without labral tear. In addition, the symptomatic hip of FAIS patients showed lower lateral trunk muscle endurance compared to the asymptomatic hip.

CLINICAL REHABILITATION IMPACT

Incorporating rehabilitation strategies that address pelvic tilt and trunk muscle strengthening in individuals with FAIS might be considered as a potential means to improve these physical impairments, pending careful evaluation of their effectiveness.

Impact of the deep squat on articular knee joint structures, friend or enemy? A scoping review

Background

The squat exercise has been shown to improve athletic performance. However, the use of the deep squat has been questioned due to claims that it may cause knee joint injuries. Therefore, the purpose of this scoping review was to synthesize existing literature concerning the impact of deep squats on knee osteoarticular health in resistance-trained individuals.

Methods

This study adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses for Scoping Reviews (PRISMA-ScR) guidelines. The original protocol was prospectively registered in Figshare (https://doi.org/10.6084/m9.figshare.24945033.v1). A systematic and exhaustive search was conducted in different databases: PubMed, Scopus, Web of Science, and SPORTDiscus. Additional searches were performed in Google Scholar and PEDro. The main inclusion criteria were the following: (1) Articles of experimental, observational, or theoretical nature, including randomized controlled trials, longitudinal studies, case reports, integrative reviews, systematic reviews, and meta-analyses(Primary studies were required to have a minimum follow-up duration of 6 weeks, whereas secondary studies were expected to adhere to PRISMA or COCHRANE guidelines or be registered with PROSPERO; (2) Peer-reviewed articles published between 2000 and 2024; (3) Publications written in English, Spanish and Portuguese; (4) Studies reporting the effects of deep half, parallel or quarter squats on the knee or evaluating squats as a predictor of injury.

Results

The keyword search resulted in 2,274 studies, out of which 15 met all inclusion criteria. These 15 studies comprised 5 cohort studies, 3 randomized controlled trials, 4 literature or narrative reviews, 1 case study, and 2 systematic reviews, one including a meta-analysis. Overall, the risk of bias (ROB) across these studies was generally low. It is worth noting that only one study, a case study, associated deep squats with an increased risk of injury, the remaining 14 studies showed no negative impact of deep squats on knee joint health.

Conclusion

The deep squat appears to be a safe exercise for knee joint health and could be included in resistance training programs without risk, provided that proper technique is maintained.

Addressing Biomechanical Errors in the Back Squat for Older Adults: A Clinical Perspective for Maintaining Neutral Spine and Knee Alignment

Background/Objectives: Falls pose a significant health risk for older adults, often due to balance disorders and decreased mobility. Methods: The ability to perform sit-to-stand transfers, which involve squatting, is crucial for daily independence. Incorporating squats into exercise routines can enhance lower body strength, reduce fall risk, and improve overall quality of life. Results: While the back squat is beneficial, proper form is essential to avoid biomechanical errors, like lumbar hyperlordosis and knee valgus. Conclusions: Health and fitness professionals, such as physical therapists and/or clinical exercise physiologists, should carefully guide older adults in performing the back squat, addressing any functional deficits, and ensuring proper technique to minimize the risk of injury and maximize the benefits.

The Quality of Functional Movements and the Back Squat in Amateur and Professional Bodybuilders

Background

It is important to assess the quality of fundamental movements, to discover deficits, evaluate mobility, balance, and stability, and identify movement dysfunction and asymmetries. However, little research has been performed on the assessment of fundamental movements with bodybuilders.

Purpose

The purpose of this research was to examine the quality of professional and amateur bodybuilders' functional movements and the quality of the back squat performance. A secondary purpose was to discern whether greater experience in bodybuilding was associated with better scores on the back squat assessement (BSA).

Study design

Cross-Sectional Cohort.

Methods

Twenty-six athletes were recruited to participate. The group of professional bodybuilders consisted of five men and six women, a total of 11 athletes. The group of amateur bodybuilders consisted of seven men and eight women, a total of 15 athletes. The Functional Movement Screen™ (FMS™) was used to assess the seven included fundamental patterns that evaluate an individual's neuromuscular control, mobility, balance, and stability. The BSA was used to assess the quality of movement, dysfunction, deficit, or compensation during the squat exercise. Statistical analyses applied non-parametric tests (Wilcoxon, Mann-Whitney U, and Friedman's) for dependent and independent samples, with significance set at p<0.05, and the Spearman correlation coefficient and Chi-square test were used to assess relationships between quantitative and qualitative variables.

Results

Overall, athletes with a higher total FMS™ score performed better on the BSA as well. The professional athletes scored 2.58 points higher than the amateurs on total FMS™ scores (p<0.001).Professional athletes scored better on the BSA than amateurs (p<0.001). A statistically significant, positive moderate correlation was revealed between the FMS™ total score and the squat total score (r=0.68; p=0.005).

Conclusions

A higher FMS™ score in bodybuilders is associated with a higher BSA score. Professional bodybuilders have higher FMS™ scores and higher BSA scores than amateurs. Greater experience in bodybuilding is associated with the compliance with several BSA criteria: trunk position, frontal knee alignment, tibial translation angle, foot position in all three back squat variations with different external loads, and descent with the training weight.

Level of Evidence

3b.

Foot Kinematics of Elite Female 59 kg Weightlifters in the 2018-2021 World Championships

BACKGROUND/OBJECTIVES

Research on elite weightlifting performance is crucial for understanding the underlying attributes of efficient techniques. This study aimed to analyze the foot characteristics of elite female weightlifters in the 59 kg category during the snatch.

METHODS

Publicly available videos from the International Weightlifting Federation World Weightlifting Championships (2018-2021) were analyzed. Excluding the 2020 competition due to the COVID-19 pandemic and more unsuccessful attempts, a total of 20 videos were selected for kinematic analysis using Kenova video analysis software. Variables included the horizontal foot distance in the start and catch phases, horizontal displacement of sideway leg separation, and maximum vertical heel height of each foot.

RESULTS

The results revealed small to moderate significant negative correlations between snatch performance and maximum heel height (right: r = -0.28, p < 0.05; left: r = -0.332 p < 0.01). Snatch performance also demonstrated a small to moderate negative correlation with sideway leg separation and foot distance in the catch phase (r = -0.275, p < 0.01; r = -0.467, p < 0.01, respectively). Maximum heel height exhibited a very strong positive correlation between feet (r = 0.853, p < 0.01).

CONCLUSIONS

A relatively narrower stance was found to be more beneficial for elite weightlifter performance. Strong coordination suggests advanced movement strategies in this complex lift. These findings contribute to the existing knowledge on weightlifting techniques and offer valuable insights for athletes and coaches seeking to improve performance in competitive environments.

A Systematic Review of Lower Limb Strength Tests Used in Elite Basketball

BACKGROUND

Basketball players rely on their lower limb strength for speed and agility. Therefore, it is important for strength and conditioning coaches to seek methods to assess and develop lower limb strength.

OBJECTIVES

This study aimed to identify tests and variables used to assess lower body strength among elite basketball players and to provide normative values for the commonly used strength tests.

METHODS

A review of PubMed, MEDLINE, Scopus, and SPORTDiscus was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. The risk of bias was assessed using the Joanna Briggs Institute cross-sectional and cohort checklists.

RESULTS

Among the twelve reviewed studies, seven strength tests and five outcome variables were used. The most frequently used lower limb strength tests were the back squat (nine studies) and isometric mid-thigh pull (IMTP) (three studies), both reporting one repetition maximum (1RM) and peak force metrics. The most frequently used lower limb strength test was the back squat among males and IMTP among females.

CONCLUSIONS

Among elite basketball players, the back squat 1RM is the most used lower limb strength test. However, across studies, a large variability was evidenced, which suggests that lower limb testing procedures are heterogeneous in this population.

Light weights are as effective as heavy weights for muscle activation in the Hammerobics exercise

PURPOSE

We previously reported that a Hammerobics exercise using weights can enhance trunk and lower extremity muscles, some studies suggested that training effects could also be expected without heavy weights. If the muscle activity induced by Hammerobics swinging with a 'light plastic ball' equals or surpasses that of the isometric static squat and synchronized squat with a heavy ball, this training approach could alleviate joint strain, fostering an exercise regimen universally accessible across generations, benefit for workouts sports and rehabilitation.

METHODS

Fifteen healthy men participated in this study. By using surface electromyography, muscle activities for the abductor hallucis, tibialis anterior, tibialis posterior, peroneus longus, rectus femoris, biceps femoris long head, semitendinosus, gluteus maximus, multifidus, and internal oblique muscles were measured during a light Hammerobics synchronized squat (HSS-light), Hammerobics synchronized squat, and conventional isometric squat, and statistically compared.

RESULTS

The front-to-back tibialis anterior activity of HSS-light was significantly higher than that of conventional isometric squat. The activities of all other muscles, except for the multifidus, were not significantly different between these exercises in the front-to-back and back-to-front phases. Compared to the Hammerobics synchronized squat, the light Hammerobics synchronized squat showed no differences in front-to-back tibialis anterior, rectus femoris, biceps femoris long head, and internal oblique activities and back-to-front abductor hallucis, tibialis anterior, rectus femoris, and internal oblique activities.

CONCLUSION

The HSS-light could stimulate muscles to the same level as the conventional isometric squat without weight bearing. While the HSS-light was less effective than the Hammerobics synchronized squat, there was no significant difference in internal oblique, rectus femoris, and tibialis anterior activities between these exercises. Hence, the HSS-light is an exercise method that can be viable approach to promoting accessible workouts sports and rehabilitation.

Are Anthropometric Measures, Range of Motion, or Movement Control Tests Associated with Lumbopelvic Flexion during Barbell Back Squats?

Background

Resistance training with the barbell back squat (BBS) exercise is practiced in sports, recreation, and rehabilitation. Although extensively debated, it is commonly believed and recommended that maintaining a neutral lumbopelvic alignment during BBS is an important technical aspect that might reduce the risk of injury. There is limited knowledge of how objectively measurable factors affect the extent to which the lumbopelvic region moves into flexion during a BBS.

Purpose

The aim of the study was to investigate the association among anthropometric measurements, range of motion in the hips and ankle joints, lumbopelvic movement control tests, and flexion of the lumbopelvic region during execution of the BBS.

Study design

Observational, cross sectional.

Methods

Eighteen experienced powerlifters and Olympic weightlifters were included and measurements of lumbopelvic movements were collected with inertial measurement units during BBS performed at 70 % of 1RM. Examination of anthropometric properties, range of motion in the hip and ankle joints, and lumbopelvic movement control tests were collected as independent variables. Linear regression analysis was used to investigate which independent variables were associated with lumbopelvic flexion during a BBS.

Results

The linear regression showed that a higher range of motion in ankle dorsiflexion could statistically significantly explain an increased amplitude of lumbopelvic flexion during the BBS. Anthropometrics, range of motion of the hips, and performance in lumbopelvic movement control tests did not show any statistically significant associations.

Conclusions

The results suggest that strength and conditioning professionals and clinicians who instruct and assess lifting technique in the BBS and/or use the BBS to assess performance or as an intervention should recognize that a higher range of motion in the ankle joints might affect lumbopelvic flexion during the BBS. In practice, the value of an individual assessment of lifting technique focusing on the goal of the movement should be emphasized.

Level of Evidence

3.

Construct Validity of the Athlete Introductory Movement Screen in Grassroots Footballers Aged 11-13 Years

BACKGROUND

This study examined the construct validity of the Athlete Introductory Movement Screen (AIMS) in children.

METHODS

Following ethics approval, parental consent, and child assent, 87 children (50 boys, 37 girls) aged 11-13 years (Mean ± SD = 12.4 ± 0.6 years) performed the AIMS and Test of Gross Motor Development (TGMD-3) in a counterbalanced order. AIMS tertiles were subsequently created, classifying children with 'high', 'medium', or 'low' movement skills.

RESULTS

A 2 (Gender) X 3 (AIMS tertile) ways analysis of covariance (ANCOVA), controlling for age and age at peak height velocity, with TGMD-3 scores as the dependant variable, indicated that TGMD-3 scores were significantly higher for girls categorised as having a medium movement skill compared to girls categorised as low, and those categorised having high movement skill compared to medium and low movement skill groups (all, p = 0.001). There was no difference in TGMD-3 scores for boys classed as having low and medium movement skills. Boys categorised as high for movement skills had significantly greater TGMD-3 scores than their peers categorised as having both low and medium movement skills (p = 0.001).

CONCLUSIONS

As the AIMS differentiates the theoretically related construct of motor competence, this study demonstrates that the AIMS has construct validity as a measure of movement skill in children aged 11-13 years.

Whole-body kinematics of squats two decades following anterior cruciate ligament injury

BACKGROUND

Kinematic studies suggest that injury of the anterior cruciate ligament (ACL) leads to long-lasting movement deficits or compensations to unload the injured knee. This study evaluated lower body kinematics during squats in individuals who suffered unilateral ACL-injury more than 20 years ago.

METHOD

Using motion capture, we compared maximum squat depth, time to complete the squat task, detailed kinematics, estimated kinetic-chain joint moments 0- 80° knee flexion, and weight distribution between legs across three groups with (ACLR, n = 27) and without ACL-reconstructive surgery (ACLPT, physiotherapy only, n = 28), and age-matched non-injured asymptomatic Controls (n = 31, average age across groups 47 years).

RESULTS

ACLPT demonstrated significantly reduced squat depth compared to Controls (p = 0.004), whereas ACLR performed similarly to Controls (p = 1.000). Other outcome variables were comparable between groups. All participants nevertheless demonstrated asymmetric weight distribution between legs but without systematic unloading of the injured side in the ACLgroups.

CONCLUSION

Expected compensatory strategies were not found in the ACL-groups, while poorer squat performance in the ACL-deficient group may depend on pure knee-joint mechanics, or lifestyle factors attributed to a less stable knee decades after ACL-injury.

Effects of high-intensity sprint exercise on neuromuscular function in sprinters: the countermovement jump as a fatigue assessment tool

Background

High-intensity sprint exercises (HIS) are central to sprinter training and require careful monitoring of athlete muscle fatigue to improve performance and prevent injury. While the countermovement jump (CMJ) may be used to monitor neuromuscular fatigue (NMF), little is known about the specific effects from HIS. The purpose of this study is to investigate the effects of HIS on the CMJ to assess its utility for assessing NMF following HIS.

Methods

Ten male collegiate 400 m sprinters completed a 400 m sprint fatigue protocol and underwent five CMJ-testing sessions (baseline, 3 minutes, 10 minutes, 1 hour and 24 hours) over two days. Three CMJ trials, performed on a force plate, were completed each trial, with rating of perceived exertion (RPE) recorded as a subjective fatigue measure. Changes in RPE, CMJ variables, force-time and power-time curves at baseline and post fatigue were assessed.

Results

Significant changes were observed in most variables following the fatigue protocol. In particular, concentric mean power remained significantly lower after 24 hours compared to baseline. In addition, the force-time curves exhibited a significant reduction in all conditions following the fatigue protocol. This decline was most pronounced within 50-75%of the concentric phase relative to baseline measurements. Conclusion. Results indicate that the CMJ may be a useful tool for monitoring fatigue in at least 400 m sprinters. These data also indicate that HIS may disproportionately reduce force output in during concentric movement. These insights may improve training prescriptions and injury prevention strategies for sprint athletes.

Retrospective review of the efficacy for sublingual ketamine in the treatment of chronic low back pain defined by a cause and central functional pain symptom focused clinical model

PURPOSE

Chronic low back pain is a leading cause of disability worldwide. A clinical model for its cause is lacking. Defining a cause based clinical model and a framework of understanding back pain in terms of peripheral structural and central functional pain is essential for optimal management.

MATERIALS AND METHODS

We describe the results of the largest published audit of 41 chronic low back pain patients, receiving outpatient sublingual ketamine therapy for defined central functional pain along with conventional peripheral structural pain management. Our clinical model assigns Movement Dysfunction as the primary cause for low back pain symptoms and restores it with Movement Therapy focused rehabilitation which is also defined. Patients were derived from a tertiary single neurosurgical specialist practice in Brisbane Australia over a three year period.

RESULTS

Severe pain and disability measurements more than halved and only 13% of patients ceased ketamine prematurely due to predominantly non-sinister side effects common to all pharmaceutical therapies. All other surveyed metrics of utility were highly favourable in this challenging cohort of chronic back pain patients biased to poor outcomes.

CONCLUSIONS

Outpatient ketamine maintains high efficacy and safety used in conjunction with a unique clinical model that describes chronic low back pain.

The Effect of Sex and Different Repetition Maximums on Kinematics and Surface Electromyography in the Last Repetition of the Barbell Back Squat

During the ascent phase of a maximal barbell back squat after an initial acceleration, a deceleration region occurs as the result of different biomechanical factors. This is known as the sticking region. However, whether this region is similar in the last repetition of different repetition maximums and if sex has an impact on biomechanics of this region are not known. Therefore, this study investigated the effect of sex (men/women) and repetition maximum (1-, 3-, 6-, and 10RM) on kinematics and surface electromyography around the sticking region. Twenty-six resistance-trained individuals comprising 13 men (body mass: 82.2 ± 8.7; age: 23.6 ± 1.9; height: 181.1 ± 6.5) and 13 women (body mass: 63.6 ± 6.6; age: 23.9 ± 4.5; height: 166.0 ± 4.5) participated in the study. The main findings were that women, in comparison to men, displayed larger trunk lean and lower hip extension angles in the sticking region, possibly due to different hip/knee extensor strength ratios. Moreover, an inverse relationship was discovered between repetition range and timing from V0 to Vmax2, in which lower repetition ranges (1- and 3RM) were shorter in Vmax2 compared to higher ranges (6- and 10RM). It was concluded that this occurrence is due to more moments of inertia in lower repetition ranges. Our findings suggest that both sex and repetition range might induce different requirements during the squat ascent.

The development of an automated assessment system for resistance training movement

Portable data collection devices and machine learning (ML) have been combined in autonomous movement analysis models for resistance training (RT) movements. However, input features for these models were mostly extracted empirically and subsequent models demonstrated limited interpretability and generalisability to real-world settings. This study aimed to investigate the utility of interpretable and generalisable modelling techniques and several data-driven feature extraction (FE) methods. This was achieved by developing machine learning movement analysis models for the barbell back squat and deadlift using markerless motion capture. 61 participants performed submaximal and maximal repetitions of both RT movements. Movement data was collected using two Azure Kinect cameras. Joint and segment kinematic variables were calculated from the collected depth imaging, and input features were extracted using traditional, manual FE methods and novel data-driven techniques. Classifiers were developed for several predefined technical deviations for both movements. Many of the addressed technical deviations could be classified with good levels of accuracy (≥70%) while the remainder were poor (55%-60%). Additionally, data-driven FE techniques were comparable to previous, traditional FE methods. Interpretable and generalisable modelling techniques can be utilised to good effect for certain classification tasks while data-driven FE techniques did not provide a consistent advantage over traditional FE methods.

"Knees Out" or "Knees In"? Volitional Lateral vs. Medial Hip Rotation During Barbell Squats

ABSTRACT

Chiu, LZF. "Knees out" or "Knees in"? Volitional lateral versus medial hip rotation during barbell squats. J Strength Cond Res 38(3): 435-443, 2024-Medial or lateral hip rotation may be present during barbell squats, which could affect the hip frontal and transverse plane moments. Male (n = 14) and female (n = 18) subjects performed squats using their normal technique and with volitional medial and lateral hip rotation. Hip net joint moments (NJM) were calculated from 3-dimensional motion capture and force platform measurements. Statistical significance was set for omnibus tests (α = 0.05) and Bonferroni's corrected for pairwise comparisons (αt-test = 0.0056). Normal squats required hip extensor, adductor, and lateral rotator NJM. Lateral rotation squats had smaller hip extensor (p = 0.002) and lateral rotator (p < 0.001) NJM and larger hip adductor (p < 0.001) NJM than normal squats. Medial rotation squats had smaller hip extensor (p = 0.002) and adductor (p < 0.001) NJM and larger hip lateral rotator (p < 0.001) NJM than normal squats. These differences exceeded the minimum effects worth detecting. As gluteus maximus exerts hip extensor and lateral rotator moments, and the adductor magnus exerts hip extensor and adductor moments, these muscles combined would be required to meet these hip demands, supporting previous research that has established these muscles as the primary contributors to the hip extensor NJM. Lateral rotation squats reduce hip lateral rotator and increase hip adductor NJM, which may be hypothesized as preferentially loading adductor magnus. Medial rotation squats increase hip lateral rotator and decrease hip adductor NJM; therefore, this variant may shift loading to the gluteus maximus.

Enhancing squat movement classification performance with a gated long-short term memory with transformer network model

Bodyweight squat is one of the basic sports training exercises. Automatic classification of aberrant squat movements can guide safe and effective bodyweight squat exercise in sports training. This study presents a novel gated long-short term memory with transformer network (GLTN) model for the classification of bodyweight squat movements. Twenty-two healthy young male participants were involved in an experimental study, where they were instructed to perform bodyweight squat in nine different movement patterns, including one acceptable movement defined according to the National Strength and Conditioning Association and eight aberrant movements. Data were acquired from four customised inertial measurement units placed at the thorax, waist, right thigh, and right shank, with a sampling frequency of 200 Hz. The results show that compared to state-of-art deep learning models, our model enhances squat movement classification performance with 96.34% accuracy, 96.31% precision, 96.45% recall, and 96.32% F-score. The proposed model provides a feasible wearable solution to monitoring aberrant squat movements that can facilitate performance and injury risk assessment during sports training. However, this model should not serve as a one-size-fits-all solution, and coaches and practitioners should consider individual's specific needs and training goals when using it.

The Significance of Maximal Squat Strength for Neuromuscular Knee Control in Elite Handball Players: A Cross-Sectional Study

Both weak muscle strength and impaired neuromuscular control has previous been suggested as risk factors for future traumatic knee injury. However, data on the relationship between these two factors are scarce. Thus, the aim of this study was to investigate the relationship and influence of the one repetition maximum (1RM) barbell squat strength on dynamic knee valgus in elite female and male handball players. In this cross-sectional study 22 elite handball players (7 females) were included. A unilateral drop jump (VDJ) test was used for the assessment of frontal plane dynamic knee valgus. Players also performed a one repetition maximum (1RM) barbell squat test, expressed relative to bodyweight (r1RM), to assess maximal strength, which were dichotomized to analyze 'weak' versus 'strong' players according to median. Correlations were noted between r1RM in squat and knee valgus angle for both the non-dominant (r = -0.54; p = 0.009) and dominant leg (r = -0.46, p = 0.03). The odds of knee valgus were eight times higher, for the dominant leg, in the weak group compared to the strong group (p = 0.03) and 27 times higher, for the non-dominant leg (p = 0.002). The outcome of the present study suggests that maximum squat strength plays an important role when it comes to neuromuscular control of the knee, and that weak handball players are at higher risk of knee valgus compared to strong players during jumping activity.

Associations Between Motor Competence and Physical Activity, Physical Fitness and Psychosocial Characteristics in Adolescents: A Systematic Review and Meta-analysis

BACKGROUND

Motor competence is an integral component of the health and performance of youth. Numerous studies support the hypothesis that motor competence interacts with perceived motor competence and physical fitness during childhood to induce positive (e.g. healthy weight status) or negative (e.g. reduced physical activity engagement) trajectories. Yet, while adolescence is a key period of rapid growth and maturation, no systematic reviews and meta-analyses have examined the association between motor competence and physical activity, physical fitness and psychosocial characteristics solely within adolescents.

OBJECTIVES

This study aimed to (1) analyse the scientific literature evaluating associations between motor competence and physical activity, physical fitness and/or psychosocial characteristics amongst adolescents; (2) evaluate the associations between motor competence and physical activity, physical fitness characteristics and/or psychosocial characteristics amongst adolescents; and (3) investigate the impact of moderator variables (i.e., age, sex, type of motor competence assessment) on the associations.

METHODS

A systematic search of electronic databases was conducted, followed by a qualitative synthesis of study methods. Random-effects meta-analyses were performed to establish the magnitude and orientation of pooled correlation coefficients between motor competence and physical activity, physical fitness and psychosocial characteristics of adolescents, whilst considering potential moderators (i.e., age, sex, type of motor competence assessment).

RESULTS

Sixty-one studies were included, totalling 22,256 adolescents. Twenty-seven different assessments of motor competence were used, with 31 studies utilising product-orientated (i.e. outcome) motor competence assessments. Meta-analyses of 43 studies showed that motor competence was positively associated with physical activity (r = 0.20 to 0.26), some physical fitness characteristics (e.g. muscular strength, cardiovascular endurance; r = 0.03 to 0.60) and psychosocial characteristics (r = 0.07 to 0.34), and inversely associated with weight status (r =  - 0.36 to - 0.10), speed (r =  - 0.31) and agility (r =  - 0.37 to 0.41). Associations with flexibility were unclear.

CONCLUSIONS

The results of this systematic review and meta-analysis support the hypothesised interactions of motor competence with physical activity (positive), physical fitness (positive except for weight status, speed and agility) and psychosocial characteristics (positive) in adolescence. However, methodological approaches vary considerably (e.g. variety of motor competence assessments utilised), with limitations of the current literature including an inadequate assessment of motor competence, a lack of longitudinal observations and a failure to account for biological maturation. Future research assessing associations between motor competence and physical activity, physical fitness and psychosocial characteristics of adolescents should include longitudinal observations of a combined motor competence assessment (i.e. process and product) and account for biological maturation. Improved evaluation using these recommendations could provide more accurate data, leading to more targeted interventions to improve adolescents' physical and psychosocial outcomes.

CLINICAL TRIAL REGISTRATION

CRD42021233441 (PROSPERO ID).

IMU-based classification of resistive exercises for real-time training monitoring on board the international space station with potential telemedicine spin-off

The microgravity exposure that astronauts undergo during space missions lasting up to 6 months induces biochemical and physiological changes potentially impacting on their health. As a countermeasure, astronauts perform an in-flight training program consisting in different resistive exercises. To train optimally and safely, astronauts need guidance by on-ground specialists via a real-time audio/video system that, however, is subject to a communication delay that increases in proportion to the distance between sender and receiver. The aim of this work was to develop and validate a wearable IMU-based biofeedback system to monitor astronauts in-flight training displaying real-time feedback on exercises execution. Such a system has potential spin-offs also on personalized home/remote training for fitness and rehabilitation. 29 subjects were recruited according to their physical shape and performance criteria to collect kinematics data under ethical committee approval. Tests were conducted to (i) compare the signals acquired with our system to those obtained with the current state-of-the-art inertial sensors and (ii) to assess the exercises classification performance. The magnitude square coherence between the signals collected with the two different systems shows good agreement between the data. Multiple classification algorithms were tested and the best accuracy was obtained using a Multi-Layer Perceptron (MLP). MLP was also able to identify mixed errors during the exercise execution, a scenario that is quite common during training. The resulting system represents a novel low-cost training monitor tool that has space application, but also potential use on Earth for individuals working-out at home or remotely thanks to its ease of use and portability.

Thoracolumbar and Lumbopelvic Spinal Alignment During the Barbell Back Squat: A Comparison Between Men and Women

Background

Maintaining neutral spinal alignment is considered important when performing the barbell back squat exercise. Since male and female lifters may differ in injury location it is important to examine whether they differ in spinal alignment during the back squat.

Objectives

The study aimed to quantify the spinal alignment in the upper and lower lumbar spine during the barbell back squat exercise in male and female lifters. Secondary aims were to compare alignment during the back squat to standing habitual lumbar spine alignment and determine whether male and female lifters differ in these aspects.

Study Design

Observational, Cross-sectional.

Methods

Competitive power- and weightlifters were recruited and performed three repetitions of the barbell back squat exercise using a load equivalent to 70% of their one-repetition maximum. Spinal alignment and range of motion were measured using inertial measurement units placed on the thoracic, lumbar and sacral spine. Data was presented descriptively and comparisons between men and women as well as spinal alignment in four different positions were done with a factorial repeated measures analysis of variance.

Results

Twenty-three (14 males, 9 females) were included. During execution of the squat, spinal alignment adjustments in the lumbar spine were made in all three planes of movement, compared to the start position, in both male and female lifters. Compared to their standing habitual posture, all lifters adjusted their upper lumbar spine to a less lordotic position when in the start position of the back squat (standing upright with the barbell on their back). Only male lifters assumed a less lordotic alignment in their lower lumbar spine in the start position compared their habitual posture.

Conclusions

Adjustments of spinal alignment, predominantly in the sagittal plane, are made during execution of the back squat in both male and female lifters. Further, lifters adopt a less lordotic alignment with a heavy barbell on their upper back, more so in male than female lifters. In conclusion, it seems that spinal alignment changes noticeably during the barbell back squat.

Level of Evidence

3©The Author(s).

Acute Effects of Isometric Conditioning Activity on the Viscoelastic Properties of Muscles and Sprint and Jumping Performance in Handball Players

ABSTRACT

Krzysztofik, M, Spieszny, M, Trybulski, R, Wilk, M, Pisz, A, Kolinger, D, Filip-Stachnik, A, and Stastny, P. Acute effects of isometric conditioning activity on the viscoelastic properties of muscles and sprint and jumping performance in handball players. J Strength Cond Res 37(7): 1486-1494, 2023-The effects of conditioning activity (CA) on muscle stiffness are currently unknown, suggesting that maximum CA effort can increase or decrease the stiffness of involved muscle groups. Therefore, this study aimed to investigate the effect of maximal isometric half-squats on the viscoelastic properties of muscles and postactivation performance enhancement (PAPE) in sprints and jumps. Twelve handball players underwent a standard warm-up and baseline assessment of muscle stiffness and tone of vastus lateralis and gastrocnemius medialis muscle, followed by 20-m sprint with intermediate measures at 5 and 10 m and countermovement jump. The PAPE was assessed by repeating the tests (at 4th, 8th, and 12th minute post-CA) after a CA protocol consisting of 3 sets of 3-second maximal isometric half-squats (EXP) or a control condition (CTRL) without any CA. The vastus lateralis stiffness in the 4th and 12th minute and muscle tone in the 4th minute post-CA significantly decreased compared with baseline ( p = 0.041, ES = 0.57; p = 0.013, ES = 0.52; p = 0.004, ES = 0.81, respectively) in the EXP condition. The 20-m sprint time significantly decreased at all post-CA time points compared with the baseline for the EXP condition ( p < 0.033) and the after values in the CTRL condition ( p < 0.036). In comparison to baseline, the 10-m sprint time decreased in the eighth minute post-CA ( p = 0.021; ES = 0.82) in the EXP condition. Moreover, it was significantly lower at the 8th and 12th minute post-CA ( p = 0.038; ES = 0.71 and p = 0.005; ES = 1.26) compared with that time points in the CTRL condition. The maximal isometric half-squats effectively improved sprint performance and significantly decreased vastus lateralis tone and stiffness. These findings offer new insights into the assessment of viscoelastic properties for evaluating the fatigue or potentiation state, which requires further investigation.

Relationship between the Young's Modulus of the Achilles Tendon and Ankle Dorsiflexion Angle at Maximum Squat Depth in Healthy Young Males

Background and Objective: Achilles tendon (AT) stiffness can reduce ankle dorsiflexion. However, whether AT stiffness affects the ankle dorsiflexion angle at a maximum squat depth remains unclear. Therefore, we aimed to investigate the relationship between the Young's modulus of the AT and ankle dorsiflexion angle at the maximum squat depth in healthy young males using shear-wave elastography (SWE). Materials and Methods: This cross-sectional study included 31 healthy young males. AT stiffness was measured using the Young's modulus through SWE. The ankle dorsiflexion angle at the maximum squat depth was measured as the angle between the vertical line to the floor and the line connecting the fibula head and the lateral malleolus using a goniometer. Results: Multiple regression analysis identified the Young's modulus of the AT at 10° of ankle dorsiflexion (standardized partial regression coefficient [β] = -0.461; p = 0.007) and the ankle dorsiflexion angle in the flexed knee (β = 0.340; p = 0.041) as independent variables for the ankle dorsiflexion angle at maximum squat depth. Conclusions: The Young's modulus of the AT may affect the ankle dorsiflexion angle at the maximum squat depth in healthy young males. Therefore, improving the Young's modulus of the AT may help increase the ankle dorsiflexion angle at maximum squat depth.

The Limitations of Anterior Knee Displacement during Different Barbell Squat Techniques: A Comprehensive Review

Based on seminal research from the 1970s and 1980s, the myth that the knees should only move as far anterior during the barbell squat until they vertically align with the tips of the feet in the sagittal plane still exists today. However, the role of both the hip joint and the lumbar spine, which are exposed to high peak torques during this deliberate restriction in range of motion, has remained largely unnoticed in the traditional literature. More recent anthropometric and biomechanical studies have found disparate results regarding anterior knee displacement during barbell squatting. For a large number of athletes, it may be favorable or even necessary to allow a certain degree of anterior knee displacement in order to achieve optimal training outcomes and minimize the biomechanical stress imparted on the lumbar spine and hip. Overall, restricting this natural movement is likely not an effective strategy for healthy trained individuals. With the exception of knee rehabilitation patients, the contemporary literature suggests it should not be practiced on a general basis.

The group mechanism in treatment: group identification and cohesion contributes to reducing chronic lower back pain by increasing personal control

PURPOSE

There is increasing recognition of the contribution that group processes, particularly identification and cohesion, make to outcomes of group delivered health treatments. This study examined the role that these particular group processes play in the treatment of lower back pain, and a theorised mechanism of personal control through which group treatment might enhance outcomes.

METHODS

Participants (N = 85) elected to either receive NeuroHAB^®, a defined functional movement therapy of 8 weeks duration, or continue with treatment-as-usual (TAU). Pain intensity and disability were assessed at baseline (T1) and post-intervention or 8 weeks later (T2), as well as at a 1-month follow-up (T3). Only the NeuroHAB^® participants additionally completed weekly questionnaires that measured treatment group identification, cohesion, and personal control.

RESULTS

NeuroHAB^® was significantly more effective than TAU in reducing pain intensity and disability at T2 and T3. Furthermore, among NeuroHAB^® recipients, stronger treatment group identification and cohesion early in the program predicted better pain outcomes over time, and this relationship was fully mediated by perceptions of personal control.

CONCLUSION

These data provide further support for the role of group identification and cohesion as a contributing mechanism of change in group-based treatments and extend this to the domain of pain management.Implications for RehabilitationA focus on defined functional movement therapy, as offered by the NeuroHAB^® group program, was found to improve pain outcomes in patients with lower back pain.A key ingredient in the NeuroHAB^® rehabilitation program was its group delivery.Group delivery supported treatment group identification and cohesion which, through enhancing the perception of personal control, reduced pain intensity and disability.

Modified Isoinertial-Based Ruffier Test in Healthy Individuals: A Feasibility Study

Cardiorespiratory fitness is an essential indicator in sports science and sports medicine that can be assessed with several tests. The Ruffier test is a submaximal test valid to estimate maximum oxygen uptake; it consists of 30 squats in 45 s, which may be challenging for inexperienced individuals. This study aims to verify the feasibility of a modified inertial-based version of the Ruffier test to assess cardiorespiratory fitness with 10 squats in 15 s. Both classic and isoinertial Ruffier tests were administered to thirty-five healthy young adults (20 men and 15 women), age 22.06 ± 2.13 years, BMI 23.87 ± 2.74. The two one-sided test confirmed the comparability of the isoinertial Ruffier test with its classic version within equivalence bounds of ±3.726. Furthermore, gender, age, body weight, the difference between peak heart rate after isoinertial squatting and resting heart rate, and the isoinertial Ruffier index are the coefficients of our best VO₂max prediction model with an adjusted R² of 0.937, sensitivity of 0.89, and specificity of 0.81. The study evidenced the feasibility of the isoinertial Ruffier test to measure cardiorespiratory fitness through a quick, safe, and short squat test easy to perform in fitness centers and primary care clinics.

Assessment of Physical Tests in 6-11 Years Old Children: Findings from the Play Lifestyle and Activity in Youth (PLAY) Study

The purpose was to evaluate selected physical tests in children and to compare the outcomes by sex. A cross-sectional study design was used to evaluate children 6-11 years who completed five physical tests: hand grip, vertical jump, sit and reach, Y-balance, and obstacle course (time and score). The outcome measures including test results were descriptively examined and compared by sex. The study participants consisted of 133 children (62 males and 71 females, with a median age of 7.8 years). Girls showed superior sit and reach performance (p = 0.002) compared with boys. Boys demonstrated better Y-balance scores (p = 0.007) and faster obstacle time (p = 0.042) than girls. Sex comparison within three age groups (6-<8 years, 8-<10 years, and 10-<12 years) showed that girls performed better on the sit and reach compared with boys in the in 6-<8 years (p = 0.009). Boys demonstrated higher Y-balance scores (p = 0.017) and faster obstacle time (p = 0.007) compared with girls in the 8-<10-year age group. These data will serve to guide future efforts to evaluate normative measures of physical literacy and guide targeted training interventions to promote sustained physical activity in children with deficits relative to their age and sex norms.

Effect of different squatting exercises on menstrual aspects, pelvic mechanics and uterine circulation in primary dysmenorrhoea: a randomised controlled trial

This was a randomised trial aimed to determine squatting exercises' effects on menstruation, pelvic mechanics, and uterine circulation in primary dysmenorrhoea. A total of 120 females with primary dysmenorrhoea were assigned into group (A), receiving yoga protocol, or groups (B, C & D), receiving yoga protocol added to modified wall squat, sumo squat, or deep squat, respectively. Menstrual pain and distress, pelvic inclination, and uterine circulation were measured before and after interventions using a pain scale, a questionnaire, palpation metre, and Doppler ultrasonography, respectively. There was a significant reduction in pain intensity in groups B & C (effect size = 3.97 & 5.89, respectively), compared to group A (effect size = 3.68), and in group C (effect size = 5.89) compared to group D (effect size = 3.94), pain subscale in the groups B, C & D (effect size = 1.69, 3.3 & 3.41, respectively), compared to group A (effect size= 2.47), water retention subscale in group D effect size 0.90 compared to group A (effect size =0.41) and in the questionnaire total scores in the groups C &D (effect size = 2.3 & 2.46, respectively) when compared to group A (effect size =1.94). Adding squatting exercises to yoga is more effective than yoga alone in reducing menstrual pain and distress.IMPACT STATEMENTWhat is already known on this subject? Physical exercises positively affect primary dysmenorrhoea in terms of decreased pain and distress, possibly through altering faulty posture. Squatting exercises affect lumbopelvic mechanics.What do the results of this study add? This study explores the effect of squatting exercises on pelvic inclination, menstrual aspects, and circulation.What are the implications of these findings for clinical practice and/or further research? Squatting exercises can be utilised to affect pelvic mechanics leading to decreased menstrual pain and distress, because of decreased pelvic congestion.

Movement Competency Screen: Rethinking the Rating

Background

Dancers are at high risk of musculoskeletal disorders. There has been a growing interest in the last few years in pre-season screening using tools to evaluate movement competency, among which is the Movement Competency Screen (MCS). It is currently scored using a categorical 3-level rating system, but this method does not seem to take into account the load level of movements. A 5-level scoring system could potentially alleviate this problem.

Hypothesis/Purpose

For each scoring system, to investigate (1) the internal consistency, and (2) the association with transversus abdominis activation (TrA), hip muscle strength and with Functional Movement screen (FMSTM) total score.

Study design

Secondary analyses of a prospective cohort study.

Methods

One hundred and eighteen professional and preprofessional dancers evolving in ballet or contemporary dance were recruited. The MCS was performed and was scored according to the 3- and 5-level scoring systems. The key variables for movement competency that were considered for convergent validity were the activation ratio of the TrA evaluated with ultrasound imaging and hip strength assessed with a handheld dynamometer. Movement competency was also measured with the FMSTM.

Results

Internal consistency was higher for the 5-level scoring of the MCS items ($*$\alpha$*$=0.548) compared to the 3-level scoring system ($*$\alpha$*$=0.494). Multiple linear regressions showed that TrA activation, hip adductor strength, and FMSTM could significantly explain 24.0% of the variance for the 5-level scoring system of the MCS whereas hip internal rotator strength and FMSTM could explain only 16.4% of the variance for the 3-level scoring system.

Conclusion

The 5-level scoring system showed better metrologic properties in terms of internal consistency and concurrent validity and therefore, should be preferred over the 3-level scoring system in future research.

Level of Evidence

Level III.

Load-velocity relationships and predicted maximal strength: A systematic review of the validity and reliability of current methods

Maximal strength can be predicted from the load-velocity relationship (LVR), although it is important to understand methodological approaches which ensure the validity and reliability of these strength predictions. The aim of this systematic review was to determine factors which influence the validity of maximal strength predictions from the LVR, and secondarily to highlight the effects of these factors on the reliability of predictions. A search strategy was developed and implemented in PubMed, Scopus, Web of Science and CINAHL databases. Rayyan software was used to screen titles, abstracts, and full texts to determine their inclusion/eligibility. Eligible studies compared direct assessments of one-repetition maximum (1RM) with predictions performed using the LVR and reported prediction validity. Validity was extracted and represented graphically via effect size forest plots. Twenty-five eligible studies were included and comprised of a total of 842 participants, three different 1RM prediction methods, 16 different exercises, and 12 different velocity monitoring devices. Four primary factors appear relevant to the efficacy of predicting 1RM: the number of loads used, the exercise examined, the velocity metric used, and the velocity monitoring device. Additionally, the specific loads, provision of velocity feedback, use of lifting straps and regression model used may require further consideration.

Self-organized Learning from Synthetic and Real-World Data for a Humanoid Exercise Robot

We propose a neural learning approach for a humanoid exercise robot that can automatically analyze and correct physical exercises. Such an exercise robot should be able to train many different human partners over time and thus requires the ability for lifelong learning. To this end, we develop a modified Grow-When-Required (GWR) network with recurrent connections, episodic memory and a novel subnode mechanism for learning spatiotemporal relationships of body movements and poses. Once an exercise is successfully demonstrated, the information of pose and movement per frame is stored in the Subnode-GWR network. For every frame, the current pose and motion pair is compared against a predicted output of the GWR, allowing for feedback not only on the pose but also on the velocity of the motion. Since both the pose and motion depend on a user's body morphology, the exercise demonstration by one individual cannot easily be used as a reference for further users. We allow the GWR to grow online with each further demonstration. The subnode mechanism ensures that exercise information for individual humans is stored and retrieved correctly and is not forgotten over time. In the application scenario, a physical exercise is performed in the presence of an expert like a physiotherapist and then used as a reference for a humanoid robot like Pepper to give feedback on further executions of the same exercise. For evaluation, we developed a new synthetic exercise dataset with virtual avatars. We also test our method on real-world data recorded in an office scenario. Overall, we claim that our novel GWR-based architecture can use a learned exercise reference for different body variations through incremental online learning while preventing catastrophic forgetting, enabling an engaging long-term human-robot experience with a humanoid robot.

A Multi-Experiment Investigation of the Effects Stance Width on the Biomechanics of the Barbell Squat

This two-experiment study aimed to explore habitual and manipulated stance widths on squat biomechanics. In experiment one, 70 lifters completed back squats at 70%, 1 repetition maximum (1RM), and were split into groups (NARROW < 1.06 * greater trochanter width (GTW), MID 1.06−1.18 * GTW and WIDE > 1.37 * GTW) according to their self-selected stance width. In experiment two, 20 lifters performed squats at 70%, 1RM, in three conditions (NARROW, MID and WIDE, 1.0, 1.25 and 1.5 * GTW). The three-dimensional kinematics were measured using a motion capture system, ground reaction forces (GRF) using a force platform, and the muscle forces using musculoskeletal modelling. In experiment two, the peak power was significantly greater in the NARROW condition, whereas both experiments showed the medial GRF impulse was significantly greater in the WIDE stance. Experiment two showed the NARROW condition significantly increased the quadriceps forces, whereas both experiments showed that the WIDE stance width significantly enhanced the posterior-chain muscle forces. The NARROW condition may improve the high mechanical power movement performance and promote the quadriceps muscle development. Greater stance widths may improve sprint and rapid change-of-direction performance and promote posterior-chain muscle hypertrophy. Whilst it appears that there is not an optimal stance width, these observations can be utilized by strength and conditioning practitioners seeking to maximize training adaptations.

Influence of commuting methods on low back pain and musculoskeletal function of the lower limbs in elementary school children: A cross-sectional study

BACKGROUND

Lower limb flexibility is known to be decreased in those living in mountainous areas, and musculoskeletal growth is often influenced by lifestyle factors. The purpose of this study was to determine the relationship between the means of transportation to school and lower limb musculoskeletal function and low back pain.

METHODS

During routine medical examinations conducted in two cities in a prefecture in 2016, a questionnaire was administered. The parents of 15,259 students who attended elementary school answered questions evaluating the following parameters: (1) anteflexion limit in the standing posture, (2) crouching failure, (3) one leg standing failure, (4) low back pain during lumbar extension, (5) lower limb alignment abnormalities, and (6) flat foot. Students were divided into a walking commuting group (13,569 students) and a vehicle commuting group (1690 students), and findings were compared between the two groups using chi-square tests.

RESULTS

In the walking and vehicle commuting groups, anteflexion limit in the standing posture was present in 23.3% and 26.1% of students, respectively (p = 0.013). Crouching failure was present in 4.6% and 7.3% of students (p < 0.001); one leg standing failure in 5.3% and 8.5% of students (p < 0.001); low back pain in 5.0% and 7.1% of students (p < 0.001); positive leg alignment abnormalities in 7.3% and 8.0% of students (p = 0.260); and flat foot in 7.4% and 8.7% of students (p = 0.067), respectively. Significant differences were observed in all four of the failure measures. No significant differences were observed in the two methods evaluating morphological abnormalities.

CONCLUSIONS

The decreased walking duration and increased sitting duration associated with vehicle commuting had little effect on lower limb morphology but could induce lower limb dysfunction and low-back pain in children. Thus, supplemental walking should be instated for children who commute by car.

AI provides congruent and prescriptive feedback for squat form: qualitative assessment of coaching provided by AI and physical therapist

Objectives: To assess style and themes of feedback provided by artificial intelligence (AI) mobile application and physical therapist (PT) to participants during bodyweight squat exercise. Methods: Research population was age 20-35, without any pre-existing condition that precluded participation in bodyweight exercise. Qualitative methodology followed directed content analysis. Cohen's kappa coefficient verified consistency between coders. Results: Both AI and PT groups had seven female and eight male participants. Three themes emerged: affirmation schema, correction paradigms and physical assessments. Average kappa coefficient calculated for all codes was 0.96, a value that indicates almost perfect agreement. Conclusion: Themes generated highlight the AI focus on congruent, descriptive and prescriptive feedback, while the PT demonstrated multipoint improvement capabilities. Further research should establish feedback comparisons with multiple PTs and correlate qualitative data with additional quantitative data on performance outcomes based on feedback.

Functional training improves the effectiveness of stretching programs for university cleaning staff

Purpose

The purpose of this study was to determine whether combining a structured stretching program with functional movement/body position training would yield additive effects on flexibility, ergonomic practices, and subjective pain levels for employees at high risk for work-related musculoskeletal disorders.

Design/methodology/approach

Nine control and 13 experimental university cleaning staff participated in a 10-week full-body stretching intervention led by undergraduate students. Experimental participants also engaged in functional movement/body position training once per week. Joint range of motion, task ergonomic form, pain level, and stretching motivation results were compared pre- and post-intervention.

Findings

Overall flexibility (+25.75 ± 3.33%) and task ergonomic form (+26.3 ± 10.5%) significantly improved and were negatively correlated with pain levels (r = −0.541 and r = −0.317, respectively). Experimental participants experienced greater improvements in shoulder (control: +16.8 ± 9.0%; experimental: +64.2 ± 11.5%) and hip (control: +31.4 ± 9.9%; experimental: +91.2 ± 19.9%) flexibility as well as in task-specific ergonomic form for vertical (control: +0.0 ± 5.3%; experimental: +35.2 ± 10.1%) and horizontal wiping (control: −4.7 ± 4.7%; experimental: +29.0 ± 7.8%). Intrinsic motivation was increased for both groups (+26.2 ± 15.4%).

Originality/value

Supplementing a workplace stretching program with functional movement/body position training has the potential to improve flexibility and decrease pain while simultaneously increasing the likelihood that cleaning staff will participate in self-directed stretching in the future. The intervention serves as a model for workplace health management and wellness-focused community building on university campuses who insource cleaning staff.

Rapid Transition to Virtual Assessment and Treatment in an Interdisciplinary Randomized Clinical Trial for Youth With Chronic Pain: Adaptations and Implications for Future Trials

OBJECTIVES

COVID-19 abruptly halted in-person clinical care and research requiring a shift to virtual assessment and treatment. This unexpected transition of a 2-arm randomized controlled trial (RCT) examining interdisciplinary graded exposure treatment (GET Living) compared with multidisciplinary pain management for youth with chronic pain provided an opportunity to implement the first remotely delivered exposure treatment and remotely delivered biomechanical assessment for pediatric chronic pain. Here we describe these new approaches and provide lessons learned to inform future efforts in digital health care.

METHODS

A total of 68 youth (M=14.2 y; 80.9% female) were enrolled in the RCT (n=31 in-person, n=5 hybrid, n=32 virtual, n=9 withdrew). Of those withdrawn, n=3 withdrew due to COVID-19 related reasons. Some RCT elements required slight modification (eg, e-consent, actigraphy deployment, recruitment, and screening), while others were significantly altered (eg, session format and lab-based biomechanical assessment). Data from exit interviews were also examined to assess perspectives on the virtual format transition.

RESULTS

Results showed an increased enrollment rate when virtual care was an option (70.7%) compared with in-person (44.3%). Equivalent rates of completion for daily assessment (in-person, 72.8%; virtual, 73.3) were also observed, and participants described enhanced experience when able to complete exercises and exposures in their home environment during session (vs. a rehabilitation gym) allowing for genuine in vivo exposures (eg, household chores, riding bicycles).

DISCUSSION

Overall, our data demonstrate acceptability, feasibility, and equivalent patient engagement to virtual treatment. Novel methods implemented in this RCT can inform trial design and measures of clinical endpoints for future digital health interventions.

Ischemia during rest intervals between sets prevents decreases in fatigue during the explosive squat exercise: a randomized, crossover study

The study aimed to evaluate the impact of ischemia, used only before particular sets of a lower limb resistance exercise on power output. Ten healthy resistance-trained males (age = 26 ± 6 years; body mass = 90 ± 9 kg; training experience = 9 ± 7 years) performed two experimental sessions (with ischemia; control without ischemia) following a randomized crossover design. During the ischemic condition, the cuffs were inflated to 60% of arterial occlusion pressure. The cuffs were applied before each set for 4.5 min and released 30 s before the start of the set as the reperfusion (4.5 min ischemia + 0.5 min reperfusion). In the control condition, ischemia was not applied. During the experimental sessions, the subjects performed the Keiser machine squat exercise protocol which consisted of 5 sets of two repetitions, at a load of 60% of one-repetition maximum (1RM), with 5 min rest intervals between sets. The repetitions were performed with maximal velocity. The two-way repeated-measures ANOVA showed a statistically significant interaction effect for power output (p < 0.01; η² = 0.26). There was also a statistically significant main effect of condition for power output (p = 0.02; η² = 0.40). The post hoc analysis for interaction did not show significant differences between conditions in particular sets. The post hoc analysis for the main effect of the condition revealed that power output was significantly lower in the control group compared to the group where ischemic was used (p = 0.02). The t-test comparisons for particular sets showed a significant lower power output in set 3 (p = 0.03); set 4 (p < 0.01) and set 5 (p < 0.01) for the control condition when compared to the ischemic condition. The results indicate that ischemia applied before each set and released 30 s prior to the start of the squat exercise did not increase power output performance. However, we observed a significantly lower decline in power for the ischemic condition (4.5 min ischemia + 0.5 min reperfusion) in sets 3–5 compared to the control condition. Thus repeated ischemia with reperfusion used between sets can be an effective form of performance enhancement by preventing or at least diminishing fatigue during resistance exercise.

The Effect of Repetitive Whole Body Cryotherapy Treatment on Adaptations to a Strength and Endurance Training Programme in Physically Active Males

Despite its potential merit in sport and exercise recovery, the implications of repetitive Whole Body Cryotherapy (WBC) during training programmes require further review due to the possibility of repetitive cold interfering with long term adaptations. This study investigated the impact of two weekly 3 min WBC sessions (30 s at −60°C, 150 s at −120°C) on adaptations to a 6 week strength and endurance training programme. Sixteen male participants (mean ± SD age 33.4 ± 9.8 years, body mass 82.3 ± 9.8 kg) randomly allocated into WBC (n = 7) and non-cryotherapy control (CON, n=9) groups completed the programme consisting of two weekly strength and plyometric training sessions and two weekly 30 min runs (70% VO₂ max). Participants were assessed for body fat, VO₂ max, muscle torque, three repetition maximum barbell squat and countermovement jump height before and after the programme. Resistance and running intensities were progressed after 3 weeks. Participants in both groups significantly improved muscle torque (WBC: 277.1 ± 63.2 Nm vs. 318.1 ± 83.4 Nm, p < 0.01, d = 0.56; CON: 244.6 ± 50.6 Nm vs. 268.0 ± 71.8 Nm, p = 0.05, d = 0.38) and barbell squat (WBC: 86.4 ± 19.5 kg vs. 98.9 ± 15.2 kg, p = 0.03, d = 0.69; CON: 91.1 ± 28.7 kg vs. 106.1 ± 30.0 kg, p < 0.01, d=0.51) following the 6 week programme. For the CON group, there was also a significant reduction in body fat percentage (p = 0.01) and significant increase in jump height (p = 0.01). There was no significant increase in VO₂ max for either group (both p > 0.2). There was no difference between WBC and CON for responses in muscle torque, 3RM barbell squat and body fat, however WBC participants did not increase their jump height (p = 0.23). Repetitive WBC does not appear to blunt adaptations to a concurrent training programme, although there may be an interference effect in the development of explosive power. Sports practitioners can cautiously apply repetitive WBC to support recovery post-exercise without undue concern on athletes' fitness gains or long term performance, particularly throughout training phases focused more on general strength development than explosive power.

Back squat mechanics in persons with a unilateral transtibial amputation: A case study

CASE DESCRIPTION

A 30-year-old person with a unilateral transtibial amputation (TTAmp) was assessed performing an Olympic-style back squat with an energy storage and return prosthetic foot.

OBJECTIVE

Determine joint-level movement strategies of an individual with TTAmp while performing an Olympic-style back squat.

STUDY DESIGN

Case study design.

TREATMENT

Back squat mechanics are evaluated in an individual with TTAmp by comparing the contribution of the ankle, knee, and hip joint to total positive and negative amputated and sound limb work.

OUTCOMES

The hip joint was the greatest contributor to total positive limb work compared with the knee and ankle, respectively, in the amputated (55.0% hip vs. 30.8% knee, P < 0.001; vs. 14.2% ankle, P = 0.001) and sound limbs (52.2% hip vs. 38.9% knee, P < 0.001; vs. 8.9% ankle, P < 0.001). The hip joint was the greatest contributor to total negative limb work compared with the ankle in both the amputated (51.0% hip vs. 15.9% ankle, P < 0.001) and sound limbs (47.3% hip vs. 10.0% ankle, P < 0.001) and the knee in the amputated limb (51.0% hip vs. 32.5% knee, P < 0.001). Ankle joint power demonstrated an atypical bimodal negative/positive/negative/positive pattern.

CONCLUSION

The individual with TTAmp used a hip-dominant joint strategy in both the amputated and sound limbs while demonstrating more potential to optimize the prosthetic foot's energy storage and return capabilities when performing a back squat.

Determining concentric and eccentric force-velocity profiles during squatting

Purpose

The force–velocity relationship of muscular contraction has been extensively studied. However, previous research has focussed either on isolated muscle or single-joint movements, whereas human movement consists of multi-joint movements (e.g. squatting). Therefore, the purpose of this study was to investigate the force–velocity relationship of isovelocity squatting.

Methods

Fifteen male participants (24 ± 2 years, 79.8 ± 9.1 kg, 177.5 ± 6 cm) performed isovelocity squats on a novel motorised isovelocity device (Kineo Training System) at three concentric (0.25, 0.5, and 0.75 m s⁻¹) and three eccentric velocities (− 0.25, − 0.5, and − 0.75 m s⁻¹). Peak vertical ground reaction forces, that occurred during the isovelocity phase, were collected using dual force plates (2000 Hz) (Kistler, Switzerland).

Results

The group mean squat force–velocity profile conformed to the typical in vivo profile, with peak vertical ground reaction forces during eccentric squatting being 9.5 ± 19% greater than isometric (P = 0.037), and occurring between − 0.5 and − 0.75 m s⁻¹. However, large inter-participant variability was identified (0.84–1.62 × isometric force), with some participants being unable to produce eccentric forces greater than isometric. Sub-group analyses could not identify differences between individuals who could/could not produce eccentric forces above isometric, although those who could not tended to be taller.

Conclusions

These finding suggest that variability exists between participants in the ability to generate maximum eccentric forces during squatting, and the magnitude of eccentric increase above isometric cannot be predicted solely based on a concentric assessment. Therefore, an assessment of eccentric capabilities may be required prior to prescribing eccentric-specific resistance training.

Reliability and Repeatability of ACL Quick Check®: A Methodology for on Field Lower Limb Joint Kinematics and Kinetics Assessment in Sport Applications

Anterior cruciate ligament (ACL) lesion represents one of the most dramatic sport injuries. Even though clinical screenings aiming at identifying subjects at risk of injuries are gaining popularity, the use of sophisticated equipment still represents a barrier towards their widespread use. This study aimed to test both reliability and repeatability of a new methodology to assess lower limb joints kinematics and kinetics directly on field with the aid of video cameras and plantar pressure insoles. Ten athletes and one case study (post ACL surgery) were assessed in a gait laboratory, while performing double leg squats, through the simultaneous acquisition of stereophotogrammetry, force plates, commercial video cameras and plantar pressure insoles. Different sources of errors were investigated and both reliability and repeatability analysis performed. Minimum and maximum RMSE values of 0.74% (right knee joint center trajectory) and 64.51%, respectively (ankle dorsi-plantarflexion moment), were detected. Excellent to good correlation was found for the majority of the measures, even though very poor and inverse between-trials correlation was found on a restricted number of trials especially for the ankle dorsi-plantarflexion moment. These findings could be used in combination with already available screening tools in order to provide more repeatable results.

Effects of Combined Resistance Training and Weightlifting on Injury Risk Factors and Resistance Training Skill of Adolescent Males

ABSTRACT

Pichardo, AW, Oliver, JL, Harrison, CB, Maulder, PS, Lloyd, RS, and Kandoi, R. Effects of combined resistance training and weightlifting on injury risk factors and resistance training skill of adolescent males. J Strength Cond Res 35(12): 3370-3377, 2021-The purpose of this study was to investigate the effects of resistance training with or without weightlifting on risk factors for injury and resistance training skill in circa-peak height velocity boys. Sixty-seven boys (aged 12-14 years) from a local secondary school were divided into 3 groups: combined resistance training (CRT), combined resistance training with weightlifting movements (CRT&WL), or a control group (CON). Experimental groups completed twice-weekly training programs over the course of an academic year. The tuck jump assessment, asymmetry measures for single-leg horizontal jump, isometric midthigh pull, and the Star Excursion Balance Test, and resistance training skill were measured pre-, mid-, and post-intervention. Only the CRT group significantly improved tuck jump assessment score pre- to post-test (p = 0.006, -20.4%, d = -0.39) but there were no clear effects on asymmetry measures for any group. Both groups significantly improved resistance training skill from pre- to post-test (CRT&WL: p = 0.002, 17.6%, d = 1.00; CRT: p = 0.026, 9.2%, d = 0.53). This study suggests that a school-based CRT program may provide significant improvements in jump landing kinematics, whereas the inclusion of weightlifting movements may provide greater improvements in resistance training skill.

Comparison of Lower Extremity Kinematics during the Overhead Deep Squat by Functional Movement Screen Score

It is unclear if the Functional Movement Screen (FMS) scoring criteria identify kinematics that have been associated with lower extremity injury risk. The purpose was to compare lower extremity kinematics of the overhead deep squat (OHDS) during the FMS between individuals who were grouped on FMS scoring. Forty-five adults who were free of injury and without knowledge of the FMS or its scoring criteria (males = 19, females = 26; height = 1.68 0.08 m; mass = 70.7 7 13.0 kg). Three-dimensional lower extremity kinematics during an OHDS were measured using a motion capture system. One-way MANOVA was used to compare kinematic outcomes (peak hip flexion angle, hip adduction angle, knee flexion angle, knee abduction angle, knee internal rotation angle, and ankle dorsiflexion angle) between FMS groups. Those who scored a 3 had greater peak hip flexion angle (F_2,42 = 8.75; p = 0.001), knee flexion angle (F_2,42 = 13.53; p = 0.001), knee internal rotation angle (F_2,42 = 12.91; p = 0.001), and dorsiflexion angle (F_2,42 = 9.00; p = 0.001) compared to those who scored a 2 or a 1. However, no differences were found in any outcome between those who scored a 2 and those who scored a 1, or in frontal plane hip or knee kinematics. FMS scoring for the OHDS identified differences in squat depth, which was characterized by larger peak hip, knee, and dorsi- flexion angles in those who scored a 3 compared with those who scored 2 or 1. However, no differences were found between those who scored a 2 or 1, and caution is recommended when interpreting these scores. Despite a different FMS score, few differences were observed in frontal or transverse plane hip and knee kinematics, and other tasks may be needed to assess frontal plane kinematics.

Design and Evaluation of an Online Squat Fitness System: Lessons Learned During the Early COVID-19 Pandemic in Japan

COVID-19 has changed our lives and limited our ability to have adequate physical activity (PA). It is necessary to replace outdoor PA with home-based fitness. However, people lack access, skills, and even motivation for home-based fitness. To address these issues, we designed a free access self-monitoring and coaching and music-based interactive online squat fitness system. Body weight squat was utilized for fitness exercise and evaluated based on three indices: knee width, hip depth, and rhythm. An online survey on changes in exercise due to the COVID-19 pandemic and exercise habits was conducted to investigate the effect of the COVID-19 pandemic on PA. We collected data from 557 respondents 5 months after the system first released and analyzed 200 visitors' performance on squat exercise and the other relevant parameters. Visitors were divided into three groups according to their age: younger, middle, and older groups. Results showed that the younger group had better squat performance than the middle and older groups in terms of hip depth and rhythm. We highlighted the lessons learned about the system design, fitness performance evaluation, and social aspects, for future study of the design and development of similar home-based fitness systems. We provided first-hand results on the relation between the COVID-19 pandemic and physical exercise among different age groups in Japan, which was valuable for policy making in the post-COVID-19 era.