Muscle Force Dynamics Across Increasing Squat Intensity Conditions in Elite Powerlifters

The growing popularity of powerlifting, which consists of the squat, bench press, and deadlift, calls for biomechanically comprehensible coaching strategies. Understanding the muscle forces at work can play a key part in this endeavor. Therefore, the aim of this study was to investigate the effects of increasing intensity in the squat on muscle forces in elite powerlifters. Twenty-nine top-ranked powerlifters from the Austrian team (age: 26.1 ± 5.4 years; 1-repetition-maximum (1-RM): 2.4 ± 0.4 × body mass) performed squats at 70%, 75%, 80%, 85%, and 90% of their 1-RM. Force plates and 3D motion capture data were used to estimate muscle forces utilizing musculoskeletal models in OpenSim. Muscle forces significantly changed with increased intensity, particularly in the gluteus maximus and semitendinosus, which showed the greatest relative increase in muscle force. The vastii muscles exhibited the highest absolute muscle forces. Notably, the hamstrings, calf, and vastii muscle forces barely increased during the deepest and most challenging region of the squat (the sticking region) with increasing intensity. Furthermore, no correlation was found between the athletes' performance level and the ratio of single-joint to multijoint hip extensor muscle forces. These findings highlight the importance of focusing on hip-dominant techniques when squatting with high intensities and supplementary training for knee extensors to optimize performance.

Effect of a lumbopelvic stability training program on lower extremity kinematic parameters in low back pain developers during single-leg squat

OBJECTIVES

Objective Altered movement patterns and lower extremity misalignment are key features in low back pain developers (LBPDs), leading to significant changes in functional movements such as squats. These changes may result in clinical low back pain (LBP) based on the kinesiopathology model. Core muscles are crucial for creating a stable platform for limb movement, but LBPDs typically have weak and poorly activated deep muscles, contributing to inefficient movement patterns. This study aims to assess the effect of a lumbopelvic stability program on lower extremity kinematics in LBPDs during single-leg squats (SLS).

DESIGN

Pre-post study.

SETTING

University dormitory gym.

PARTICIPANTS

Thirty female participants identified as LBPDs, divided into two groups of experimental (n = 15) and control (n = 15).

MAIN OUTCOME MEASURES

Kinematic variables, including hip and knee flexion and abduction, and ankle dorsiflexion and abduction (eversion), were measured during SLS using two-dimensional video analysis before and after the intervention.

RESULTS

Significant differences were found in hip flexion (F = 13.36, p = 0.001), hip abduction (F = 73.42, p = 0.001), knee flexion (F = 23.65, p = 0.001), and knee abduction (F = 13.37, p = 0.001) post-intervention.

CONCLUSION

A 6-week lumbopelvic stability program improved hip and knee kinematics in LBPDs, highlighting the importance of core stability in optimizing movement and potentially preventing future LBP.

Squatting Posture Grading System for Screening of Limited Ankle Dorsiflexion

Objective

To evaluate the effectiveness of a squatting posture grading system established to screen for limited ankle dorsiflexion.

METHODS

The squat posture grading system categorizes subjects' squat posture into three grades. Grade 1 is defined as being able to maintain a squatting posture with heels on the ground in full ankle dorsiflexion without effort. Grade 2 is defined as being able to perform the same position, but unable to maintain the position for more than 5 seconds or requiring trunk and leg muscle efforts to maintain the position. Grade 3 is defined as being unable to maintain the same position and falling backwards immediately if attempted to touch the ground with heels. Next, subjects' ankle dorsiflexion angles were directly measured in knee flexed and extended position by goniometer.

RESULTS

Out of the 92 total subjects, 35 were in grade 1, 18 were in grade 2, and 39 were in grade 3. The average ankle dorsiflexion angle with knee flexed position were 23.13° for grade 1, 16.03° for grade 2, and 9.31° for grade 3. The average ankle dorsiflexion angle with knee extended position were 15.16° for grade 1, 7.92° for grade 2, and 3.40° for grade 3. Ankle dorsiflexion angles showed a significant decrease from grade 1 to 3 (p<0.05).

Conclusion

The squatting posture grading system defined in this study effectively graded the subjects based on the difference in their average ankle dorsiflexion angle. This system could be used as a quick screening method for limited ankle dorsiflexion.

Acute Physiological and Perceptual Responses to Six Body-Weight Squat Exercise Variations

Adequate exercise prescription requires a deep understanding of the body's response to exercise. This study explored the responses of heart rate (HR), muscle oxygen saturation (SmO2), and perceived exertion (RPE) during six body-weight squat exercise variations. A total of 15 recreationally active participants (age: 28.2 ± 8.0 years; body mass: 71.1 ± 11.2 kg; height: 1.73 ± 0.08 m) were recruited. Six body-weight squat variations (deep, jumping, single-leg, uneven, unstable, and wall-sit) were randomly performed for 90 s. Results revealed that the jumping squat promoted a higher average and peak HR (165.3 ± 14.5 and 146.1 ± 14.8 bpm, respectively), and a lower average SmO2 and higher deoxygenation SmO2 in the soleus muscle (40.3 ± 15.4 and 46.0 ± 11.4%, accordingly). No differences were observed in recovery time or in the same SmO2 derived-parameters in the vastus lateralis muscle. The jumping variation promoted a greater response at a physiological level, both centrally, related to cardiovascular response, and peripherally, related to soleus SmO2. It was also the more demanding variation at both the overall and lower limb muscular level of RPE. This holistic view allows a precise identification of the response patterns in body-weight squat exercise variations to an acute session, with a training intervention providing additional information.

Evaluating the Impact of Optokinetic Stimulation on Weight Balance and Muscle Strength in Healthy Individuals in Virtual Reality During Squats

Background Asymmetry in lower limb muscle strength and weight-bearing imbalance, commonly observed among athletes, individuals with unilateral impairments, and stroke survivors, require targeted interventions to correct left-right imbalances. Such corrections are essential for enhancing athletic performance, minimizing injury risks in athletes, and improving gait functionality and daily activity efficiency in patients. This study explored, in healthy participants, the potential of combining squat training with optokinetic stimulation (OKS) in an immersive environment to improve left-right balance and address asymmetries in muscle activity and weight distribution. Methodology OKS was delivered using a random dot pattern rotating around either the longitudinal axis (horizontal OKS (HOKS)) or the frontal axis (torsional OKS (TOKS)) during squats. Weight-bearing was evaluated by analyzing the center of pressure (CoP) position and foot pressure (FP). Electromyography (EMG) activity was recorded from the following four leg muscles: the vastus lateralis, vastus medialis, semitendinosus, and biceps femoris. Results Both HOKS and TOKS increased the CoP sway during squats by 38.6% and 58.6%, respectively, compared to the control. However, only TOKS caused a significant weight-bearing shift toward the stimulus side. During TOKS, FP significantly increased by 10.9% on the stimulus side and decreased by 8.9% on the non-stimulus side, reinforcing the weight-bearing shift. Additionally, EMG activity was significantly elevated by 3.4% on the stimulus side during TOKS, both during the flexion and extension phases. Safety was confirmed during all measurements. Conclusions These findings indicate that TOKS induces a shift in weight-bearing and enhances muscle activity, highlighting its potential as a therapeutic intervention for correcting asymmetrical patterns in muscle activity and weight distribution.

A Systematic Review of the Effects of Low-Carbohydrate Diet on Athletic Physical Performance Parameters

A low-carbohydrate diet (LCD) or ketogenic diet is commonly used by individuals who want to achieve ketosis, which can boost fat metabolism, increase insulin sensitivity, and reduce blood sugar spikes. However, many athletes are hesitant to utilize a diet that specifically restricts the intake of carbohydrates, an important source of energy for physical activity. Athletes usually adopt a high-carbohydrate or high-protein diet, depending on their goals. This review aims to examine the evidence for the impact of an LCD on athletes' aerobic, anaerobic, and upper and lower body strength performance. A systematic review of original studies was conducted for articles indexed in PubMed that utilized an LCD in athletes and reported athletic performance values. A total of 19 studies were included in the final synthesis. An LCD may aid in maintaining or increasing upper and lower body strength. However, this type of diet provides no consistent benefit and may even negatively impact some measures of aerobic and anaerobic performance. Taken together, no strong evidence indicates the benefit of an LCD on athletic performance. Athletes wishing to modify their diet for improved performance should consider possible diets with specific training and performance goals in mind.

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.

Portions of the force-velocity relationship targeted by weightlifting exercises

We compared the force-velocity (F-V) characteristics between jump squat (JS) and weightlifting (hang clean [HC] and HC pull [HCP]) to determine lower limb F-V portions targeted by weightlifting exercises. Ten weightlifters performed JS at 0% (body weight only) to 70% of their one-repetition maximum (1RM) for back squat, and HC and HCP at 30‒90% and 30‒110% of their 1RM for HC, respectively. Force and velocity values at each relative load were plotted to determine the F-V features of JS, HC, and HCP. Linear regression was used to evaluate each participant's JS F-V results to obtain individual F-V relationships. Regression equations evaluated the JS force at a given velocity for each relative load of HC and HCP. HC produced significantly less force than JS at given velocities for 30%, 40%, and 50% 1RM. Furthermore, HCP produced significantly less force than JS at a given velocity for 30% 1RM and exhibited less force than JS at a given velocity for 40% 1RM with moderate effect size. HC and HCP produce comparable forces to JS within the velocity ranges of 60‒90% and 50‒110% 1RM, respectively. Thus, weightlifting exercises target low‒moderate-velocity portion of the lower limb F-V relationship.

A systematic review and meta-analysis investigating the impact of exercise interventions on heart rate variability in hemodialysis patients

Patients with chronic kidney disease have a high incidence of cardiovascular diseases, and autonomic dysfunction has a determinant role in the relevant declines. Physical exercise influences heart rate variability and cardiac autonomic modulation. Thus, our objective was to systematically review, with a meta-analysis, the correlation between physical exercise interventions and alterations in cardiac autonomic modulation in hemodialysis patients. A customized research strategy was used across four databases. The search yielded 392 studies, with eight randomized clinical trials included (396 participants), indicating that the investigated indices favor the intervention group by increasing autonomic activity. The exercise training probably increases the standard deviation of all NN intervals (20.71 ms CI 95% [9.55, 31.87], p < 0.001, I²=95%) compared to the control group and showing an moderate certainty, was the most commonly used index (seven studies). Mean RR (35.57 ms CI 95% [14.56, 56.57], p = 0.91, I²=0%), the root mean square sum of squares of differences between NN intervals (10.55 ms CI 95% [6.75, 14.34], p = 0.37, I²=4%), and LF/HF (0.28 ms (n.u) [0.11, 0.44], p = 0.18, I²=39%) were also in favor of the training group. However, based on the GRADE analysis we are uncertain whether Mean RR can increase after an exercise intervention, as well RMSSD and LF/HF may increase slightly, we obtained low certainty of this evidence. The exact magnitude of the impact of physical training on the alteration of cardiac autonomic modulation in this patient population has yet to be conclusively defined.

Development of a comprehensive clinical assessment protocol for low back and hip pain in powerlifters: a feasibility study

BACKGROUND

Low back and hip pain problems are frequent in powerlifting. There is a lack of information on the specific pain phenotypes and specific impairments in body function associated with these pain problems, as well as how to reach a clinical diagnosis relevant for powerlifters' pain problems. Therefore, the aim was to develop a comprehensive clinical assessment protocol for pain and function in powerlifters with low back and/or hip pain and evaluate its feasibility for use in further epidemiological or clinical studies of powerlifters.

METHODS

The study was conducted in two phases. In phase one, the protocol was developed according to literature regarding musculoskeletal assessment and sports injuries, and in phase two, feasibility was evaluated. Eight powerlifters with low back/hip pain were included in phase two. Four of them were examined independently by two physical therapists, and the other four were examined by one of the physical therapists. The time spent on the examination, whether the physical therapists could reach a clinical diagnosis without adding items to the protocol, and whether the two physical therapists were consistent in terms of the clinical diagnosis, were evaluated.

RESULTS

The protocol was developed including subjective examination, physical examination, and a clinical diagnosis based mainly on signs and symptoms of associated neurophysiological pain mechanisms and the specific impairments in body functions associated with the powerlifter's pain problem. The protocol met the feasibility criteria. The examination lasted approximately 1 h, no items needed to be added, and both physical therapists were able to make a consistent clinical diagnosis. Visual observation and alteration of movement strategy of the squat/deadlift were thought to be crucial for assessing the powerlifters' pain problem.

CONCLUSIONS

This is the first comprehensive clinical assessment protocol developed to describe powerlifters' pain problems/injuries with a clinical diagnosis based on the dominating neurophysiological pain mechanism and impairments in body functions. However, before use in larger studies, it is recommended that the protocol be further evaluated by a larger number of physical therapists and powerlifters to evaluate its reliability and whether the content of the protocol should be further expanded.

Comparison of Velocity and Estimated One Repetition Maximum Measured with Different Measuring Tools in Bench Presses and Squats

The aim of this study was to compare barbell velocities at different intensities and estimated 1-RM with actual 1-RM measured with different measuring tools in bench presses and squats. Fourteen resistance-trained athletes (eight men, six women, age 28.1 ± 7.5 years, body mass 78.1 ± 12.2 kg, body height 1.73 ± 0.09 m) performed bench presses and squats at five loads varying from 45 to 85% of one repetition maximum (1-RM), together with 1-RM testing, while measuring mean, mean propulsive, and peak barbell velocity with six different commercially used inertial measurement units (IMUs) and linear encoder software systems attached to the barbell. The 1-RM was also estimated based upon the load-velocity regression, which was compared with the actual 1-RM in the bench press and squat exercises. The main findings were that GymAware revealed the highest reliability along with minimal bias, while Musclelab and Vmaxpro showed moderate reliability with some variability at higher loads. Speed4lifts and PUSH band indicated greater variability, specifically at higher intensities. Furthermore, in relation to the second aim of the study, significant discrepancies were found between actual and estimated 1-RM values, with Speed4lifts and Musclelab notably underestimating 1-RM. These findings underscore the importance of selecting reliable tools for accurate velocity-based training and load prescription.

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.

Kinematic analysis of the back squat at different load intensities in powerlifters and weightlifters

Introduction

This study aimed to evaluate the angular kinematics of the hip, knee, ankle, and the linear kinematics of the barbell during the back squat (BS) at different load intensities in powerlifters and weightlifters.

Methods

Seventeen athletes were recruited (n = 14 powerlifters; n = 3 weightlifters). The 1-RM of the BS of each participant was calculated and, 1-week after, each participant was asked to perform 5 trials of the BS at different load intensities (i.e., 60%, 70%, 80%, 90%, 100%) of the 1-RM. An action camera recorded the execution of each BS trial in the sagittal plane and, afterward, the videos were analyzed by measuring the range of motion (ROM) of hip, knee, and ankle for the angular kinematics, and the timing, distances, speeds, and accelerations of the barbell for the linear kinematics.

Results

Regarding the angular kinematics, no significant differences were found in the parameters in the starting and ending positions among the 5 trials, while a significant decrease was found in the hip relative angle (p = 0.026) in the maximum flexion position as load intensity increased. Regarding the linear kinematics, a significant difference was found in the descent acceleration (p = 0.049) in the descent phase, while a significant difference was found in the ascent speed (p < .001) and vertical speed of ascent (p < .001) in the ascent phase, which decreased as load intensity increased.

Discussion

Our findings show that the angular and linear kinematics of BS change as load intensity increases.

Oxygenation Kinetics of Three Quadriceps Muscles During Squatting Exercise in Trained Men

This study aimed to monitor the oxygenation and blood supply in three quadriceps muscles [the vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF)] during squatting exercise to exhaustion. Eighteen young resistance-trained males performed five sets of 15 back squats in a Smith machine, with two warm-up sets [at 14% and 45% of the 15-repetition maximum (15RM)] and three main sets at 100% of the 15RM. Three near-infrared spectroscopy devices were attached to the VL, VM, and RF to record the muscle oxygen saturation (SmO2) and total hemoglobin (tHb, an index of muscle blood supply). The blood lactate concentration was measured after each set with a portable analyzer. The SmO2 and tHb data were analyzed by repeated-measures two-way ANOVA (muscle × set). Lactate data were analyzed by repeated-measures one-way ANOVA. The statistical significance was set at α = 0.05. The SmO2 dropped during each set (hitting zero in many instances) and was reinstated during recovery. The three main sets caused severe deoxygenation in the VL and VM, as opposed to moderate deoxygenation in the RF. From one set to the next, the initial value and the drop in the SmO2 increased, whereas the final SmO2 value decreased. The tHb increased in the VL, did not change considerably in the VM, and decreased in the RF during each set. The blood lactate concentration increased gradually from one set to the next, reaching about 10 mmol/L. These findings show pronounced differences in the physiological and metabolic responses of three quadriceps muscles to squatting exercise, thus highlighting the importance of studying such responses at multiple sites.

External focus instruction using a soft paper balloon on muscle activation patterns in isometric hip abduction exercises: A comparative analysis with external resistance tools

BACKGROUND

This study investigates a novel isometric method utilizing an external focus instruction technique with a soft paper balloon. By emphasizing control to avoid crushing the balloon, this method promotes co-contraction of muscles without exerting pressure on the object. We aim to evaluate differences in muscle activation patterns during isometric hip abduction exercises between the paper balloon task and tasks using external resistance (hard plastic, non-elastic, and elastic bands), and further determine their influence on the contralateral side.

METHODS

Thirteen healthy adult males aged 20-28 years were recruited. Six trunk muscles (transversus abdominis [TrA], internal oblique [IO], external oblique, rectus abdominis, multifidus [MF], and lumbar erector spinae) and five lower-extremity muscles (gluteus maximus [GMax], gluteus medius [GMed], adductor longus, rectus femoris [RF], and biceps femoris [BF]) were measured using surface and fine-wire electrodes to compare the different isometric hip abduction exercises.

RESULTS

The muscle activity did not differ between the abduction sides except for GMax and GMed with the elastic band and RF and BF with the hard plastic (p > 0.05).

CONCLUSIONS

The trunk muscles (TrA, IO, and MF) were similarly activated with the paper balloon and external loading tasks; however, the paper balloon task activated trunk muscles without bearing weight, potentially avoiding pressure on the spine, knee, or hip joints. Moreover, all tasks showed muscle activation on the opposite side of the body.

Are 7 MM neoprene knee sleeves capable of modifying the knee kinematics and kinetics during box jump and front squat exercises in healthy CrossFit practitioners? An exploratory cross-sectional study

OBJECTIVE

Investigate whether wearing 7 mm neoprene knee sleeves during the front squat and box jump CrossFit exercises change the biomechanics of the knee joint.

DESIGN

a cross-sectional exploratory study.

SETTING

Laboratory-based.

PARTICIPANTS

Seventeen male healthy CrossFit participants completed front squats and box jumps with knee sleeves (KS) and without knee sleeves (WKS).

MAIN OUTCOMES MEASURES

Kinematic and kinetic data of the knee in the sagittal, frontal and transverse planes were obtained for the two tasks and under the two experimental situations. The maximum load lifted on 1 MR test was recorded under KS and WKS conditions. The GROC scales were applied after each exercise and condition to assess participants' self-reported perception of stability.

RESULTS

The KS reduced the knee range of motion in the transverse plane during box jump (p = 0.029) and the peak knee external adduction moment (p = 0.047) during front squat compared to WKS. The 1RM during front squat increased in KS compared to WKS (p < 0.001). Most participants (94%) reported that they felt better stability using KS and all participants (100%) believed that knee sleeves would avoid knee pain.

CONCLUSION

neoprene knee sleeves have little impact on the biomechanics of the knee joint during CrossFit. However, participants reported improved knee stability.

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.

Movement pattern definitions for resistance training behavior measurement in diabetes

Type 2 diabetes can result in debilitating vascular complications, and resistance training (RT) is an effective therapy for improving cardiovascular outcomes. However, only 10-30% of adults meet the public health guidance for RT. While current RT guidelines focus on targeting major muscle groups, guidance specific to simplified movement categorization may augment understanding of RT programming and improve uptake and outcomes. Current movement pattern definitions and descriptions lack clarity, accuracy, and consistency. This paper proposes movement definitions and descriptions to be used for RT intervention design and prescription, and includes the following categories: hip, knee, ankle, vertebral column, vertical push, horizontal push, vertical pull, and horizontal pull. These categories are intended to aid clinicians, researchers, and trainers in RT surveillance and RT intervention design for improving vascular complications in type 2 diabetes. Simplified RT program design using these categories may also facilitate greater RT program understanding and adherence for patients.

Muscle activation in the lower limb muscles in individuals with dynamic knee valgus during single-leg and overhead squats: a meta-analysis study

BACKGROUND

Dynamic knee valgus (DKV) is a risk factor for non-contact anterior cruciate ligament (ACL) injuries. Understanding the changes in the electromyographic activity of the lower extremity muscles in individuals with DKV helps trainers design ACL injury prevention exercises. Therefore, the present meta-analysis aimed to investigate the muscle activation of the lower limb muscles in individuals with DKV during single-leg and overhead squats.

METHODS

Articles with titles, abstracts, and full texts were searched and screened independently by two reviewers in the Web of Science, Scopus, PubMed, and Google Scholar databases, without restrictions on publication date and in English using specified keywords from their inception to January 5, 2024. The quality of articles was evaluated using a modified version of the Downs and Black quality checklist. This meta-analysis used mean difference (MD) to compare the muscle activity patterns between individual with DKV and healthy individuals. Heterogeneity was detected using I-square (I2) test.

RESULTS

In total, four papers with 130 participants were included in the study. Evidence showed a significant difference between the DKV group and the healthy group regarding the activities of the adductor magnus (MD: 6.25, P < 0.001), vastus medialis (MD: 13.23, P = 0.002), vastus lateralis (MD: 11.71, P = 0.004), biceps femoris (MD: 3.06, P = 0.003), and tibialis anterior muscles (MD: 8.21, P = 0.02). Additionally, muscle activity in the DKV group was higher than that in the healthy group.

CONCLUSIONS

This meta-analysis reveals distinct muscle activation patterns in individuals with dynamic knee valgus (DKV), with increased activity in key muscles suggesting compensatory responses. These findings underscore the need for targeted rehabilitation to address muscle imbalances and improve knee stability.

Interjoint Coordination at Different Squatting Speeds in Healthy Adults

Background Squatting is commonly used in various settings to enhance muscle strength and performance. Both fast and slow squats have advantages as training to improve muscle function in the lower extremity muscles. Movement speed affects the variability of interjoint coordination and decreased variability can lead to overuse injuries owing to repetitive mechanical loading on the lower extremity joints. However, only a few studies have focused on interjoint coordination during squatting. This study aimed to clarify the kinematic and kinetic differences, as well as the interjoint coordination, during squatting at different speeds. Methodology Healthy young participants with no locomotor disease were recruited to perform descending parallel squats at different speeds (one, three, and five seconds) using a 3D motion analysis system and force plates. Joint moments and continuous relative phases were calculated and compared between the conditions. Results There were no significant differences in the mean values of lower limb joint moments among the three speed conditions. However, the mean absolute values of the continuous relative phase between the ankle and hip joints and the mean standard deviation of the continuous relative phase between each lower limb joint were significantly lower in the high-speed condition than in the medium- and low-speed conditions. Additionally, in the high-speed condition, the knee joint moved ahead of the hip joint in the knee-hip joint phase coordination pattern. Conclusions The joint load per unit time remained constant across all speed conditions. High-speed squatting may adapt to mechanical loading on the joints, although the knee joint moves ahead of the hip joint, exhibiting a highly coordinated movement. Conversely, low-speed squatting may reduce the risk of disability owing to the high variability of interjoint coordination. Therefore, squatting training should be based on individual characteristics and objectives.

A Biomechanical Comparison Between a High and Low Barbell Placement on Net Joint Moments, Kinematics, Muscle Forces, and Muscle-Specific Moments in 3 Repetition Maximum Back Squats

ABSTRACT

Larsen, S, de Zee, M, Kristiansen, EL, and van den Tillaar, R. A biomechanical comparison between a high and low barbell placement on net joint moments, kinematics, muscle forces, and muscle-specific moments in 3 repetition maximum back squats. J Strength Cond Res 38(7): 1221-1230, 2024-This study aimed to investigate the impact of a high barbell vs. low barbell placement on net joint moments, muscle forces, and muscle-specific moments in the lower extremity joints and muscles during maximum back squats. Twelve recreationally trained men (age = 25.3 ± 2.9 years, height = 1.79 ± 7.7 m, and body mass = 82.8 ± 6.9 kg) volunteered for the study. A marker-based motion capture system and force plate data were used to calculate the net joint moments, and individual muscle forces were estimated using static optimization. Muscle forces were multiplied by their corresponding internal moment arms to determine muscle-specific moments. Statistical parametric mapping was used to analyze the effect of barbell placement as time-series data during the concentric phase. The 3 repetition maximum barbell load lifted by the subjects was 129.1 ± 13.4 kg and 130.2 ± 12.7 kg in the high bar and low bar, which were not significantly different from each other. Moreover, no significant differences were observed in net joint moments, muscle forces, or muscle-specific moments for the hip, knee, or ankle joint between the low- and high bar placements. The findings of this study suggest that barbell placement plays a minor role in lower extremity muscle forces and moment-specific moments when stance width is standardized, and barbell load lifted does not differ between barbell placements among recreationally resistance-trained men during maximal back squats. Therefore, the choice of barbell placement should be based on individual preference and comfort.

Comparison of joint kinematics between upright front squat exercise and horizontal squat exercise performed on a short arm human centrifugation

This study compared the joint kinematics between the front squat (FS) conducted in the upright (natural gravity) position and in the supine position on a short arm human centrifuge (SAHC). Male participants (N = 12) with no prior experience exercising on a centrifuge completed a FS in the upright position before (PRE) and after (POST) a FS exercise conducted on the SAHC while exposed to artificial gravity (AG). Participants completed, in randomized order, three sets of six repetitions with a load equal to body weight or 1.25 × body weight for upright squats, and 1 g and 1.25 g at the center of gravity (COG) for AG. During the terrestrial squats, the load was applied with a barbell. Knee (left/right) and hip (left/right) flexion angles were recorded with a set of inertial measurement units. AG decreased the maximum flexion angle (MAX) of knees and hips as well as the range of motion (ROM), both at 1 and 1.25 g. Minor adaptation was observed between the first and the last repetition performed in AG. AG affects the ability to FS in naïve participants by reducing MAX, MIN and ROM of the knees and hip.

Relationship among the COM Motion, the Lower Extremity and the Trunk during the Squat

Squatting is a common motion in activities of daily living and is frequently used in training programs. Squatting requires a shift of the body in both vertical and anterior-posterior directions. Postural control during squatting is considered a mixed strategy; however, details and roles of the trunk and lower limb joints are unclear. The purpose of this study was to investigate the relationship among the kinematics of the lower limb, the trunk and the center of mass (COM) descent during squatting. Twenty-six healthy young adults performed repeated parallel squats. Lower limb joint and trunk angles and the COM were analyzed using a 3D motion analysis system. We evaluated the relationship between the kinematics and the squat depth by performing correlation analysis and multiple linear regression analysis. The ankle was the first to reach its maximum angle, and the remaining joints reached their maximum angles at the maximum squat depth. The knee joint motion and the squat depth were significantly correlated and there was a correlation between the hip and the ankle joint motion and the anteroposterior displacement of the COM during squatting. Multivariate linear regression analysis indicated that squat depth was predicted by both the knee and ankle motion and that anteroposterior displacement of the COM was predicted by the hip, ankle, and knee joint motion. The knees contributed to the vertical COM motion during squatting, while the hips contributed to the COM motion in the anteroposterior direction. On the other hand, the ankles contributed to COM motions in both the vertical and anteroposterior directions during squatting.

Marker location and knee joint constraint affect the reporting of overhead squat kinematics in elite youth football players

Motion capture systems are used in the analysis and interpretation of athlete movement patterns for a variety of reasons, but data integrity remains critical regardless. The extent to which marker location or constraining degrees of freedom (DOF) in the biomechanical model impacts on this integrity lacks consensus. Ten elite academy footballers performed bilateral overhead squats using a marker-based motion capture system. Kinematic data were calculated using four different marker sets with 3DOF and 6DOF configurations for the three joint rotations of the right knee. Root mean squared error differences between marker sets ranged in the sagittal plane between 1.02 and 4.19 degrees to larger values in the frontal (1.30-6.39 degrees) and transverse planes (1.33 and 7.97 degrees). The cross-correlation function of the knee kinematic time series for all eight marker-sets ranged from excellent for sagittal plane motion (>0.99) but reduced for both coronal and transverse planes (<0.9). Two-way ANOVA repeated measures calculated at peak knee flexion revealed significant differences between marker sets for frontal and transverse planes (p < 0.05). Pairwise comparisons showed significant differences between some marker sets. Marker location and constraining DOF while measuring relatively large ranges of motion in this population are important considerations for data integrity.

Modified Squat Test for Predicting Knee Muscle Strength in Older Adults

BACKGROUND

Methods for evaluating the strength of the knee extensor muscles play a vital role in determining the functionality of the lower limbs and monitoring any alterations that occur over time in older individuals. This study assessed the validity of the Modified Squat Test (MST) in predicting knee extensor muscle strength in older adults.

METHODS

This study included a total of 110 older adults. We collected demographic information such as sex, age, body weight, height, and thigh circumference. Muscle strength was assessed by measuring the maximum voluntary isometric contraction of the knee extensors, and by performing the MST (5 and 10 repetitions) and single-leg standing balance test. Stepwise multiple linear regression analysis was used to investigate multiple factors impacting the prediction of knee extensor strength.

RESULTS

Factors such as age, sex, thigh circumference, performance on the single-leg standing eye-open (SSEO) task, and the time required to complete the 10 MST repetitions together explained 77.8% of the variation in knee extensor muscle strength among older adults. We further developed a predictive equation to calculate strength as follows: strength = 36.78 - 0.24 (age) + 6.16 (sex) + 0.19 (thigh circumference) + 0.05 (SSEO) - 0.54 (time required to complete 10 MST repetitions) ± 5.51 kg.

CONCLUSION

The 10-repetition MST is an invaluable instrument for establishing an equation to accurately predict lower limb muscle strength.

Knee wobbling during the single-leg-squat-and-hold test reflects dynamic knee instability in patients with anterior cruciate ligament injury

We propose using the single-leg squat-and-hold (SLSH) task with kinematic analysis to objectively measure dynamic knee stability after anterior cruciate ligament (ACL) injury. There are three objectives of this study: to compare the knee kinematics of ACL-deficient patients and healthy controls by capturing knee wobbling during the SLSH task, to detect kinematic changes after ACL reconstruction, and to correlate the kinematic variables with self-reported knee function. Twenty-five ACL-deficient participants and 18 healthy matched participants were recruited. The knee kinematics involving both the magnitudes and frequency of motion fluctuation was captured during SLSH by 3D motion analysis system (Vicon). Compared to the limbs of the control participants, the ACL involved limbs exhibited a greater range of flexion-extension (4.33 ± 1.96 vs. 2.73 ± 1.15; p = 0.005) and varus-valgus (2.52 ± 0.99 vs. 1.36 ± 0.42; p < 0.001). It also inhibited higher frequency of flexion-extension (4.87 ± 2.55 vs. 2.68 ± 1.23; p = 0.003) and varus-valgus (3.83 ± 2.59 vs. 1.42 ± 0.55; p < 0.001). The range of flexion-extension (4.50 ± 2.24 vs. 2.90 ± 1.01; p = 0.018), frequency of flexion-extension (4.58 ± 2.53 vs. 3.05 ± 1.80; p = 0.038) and varus-valgus (3.46 ± 2.11 vs. 1.80 ± 1.23; p = 0.022) was reduced after ACL reconstruction. Increased frequency of knee varus-valgus was correlated with lower IKDC score (r = -0.328; p = 0.034). Knee wobbling was more prominent in ACL-deficient patients, which was associated with poor knee function. SLSH task with kinematic analysis appears to be a potential assessment method for monitoring dynamic knee stability after ACL injury.

The Force-Vector Theory Supports Use of the Laterally Resisted Split Squat to Enhance Change of Direction

ABSTRACT

Cooley, C, Simonson, SR, and Maddy, DA. The force-vector theory supports use of the laterally resisted split squat to enhance change of direction. J Strength Cond Res 38(5): 835-841, 2024-The purpose of this study was to challenge the conventional change of direction (COD) training methods of the modern-day strength and conditioning professional. A new iteration of the modified single-leg squat (MSLS), the laterally resisted split squat (LRSS), is theorized to be the most effective movement for enhancing COD performance. This study lays out a rationale for this hypothesis by biomechanically comparing the LRSS, bilateral back squat (BS), and MSLS with a COD task (90-degree turn). One repetition maximum (1RM) for LRSS, MSLS, and BS was measured for 23 healthy active female subjects. Peak ground reaction forces (GRF) for the dominant leg were recorded when performing COD and the LRSS, MSLS, and BS at 70% 1RM. Peak frontal plane GRF magnitude and angle were calculated for each task and submitted to repeated measures ANOVA. Peak GRF magnitude was significantly larger for COD (2.23 ± 0.62 body weight) than the LRSS, MSLS, and BS (p ≤ 0.001). Peak GRF angle was not significantly different between COD and the LRSS (p = 0.057), whereas the MSLS and BS (p < 0.001) vector angles were significantly greater than COD. In this application of the force-vector theory, the LRSS more closely matches COD than the MSLS or BS. Thus, the LRSS has the greater potential to enhance COD.

A Biomechanical Comparison Between the Safety-Squat Bar and Traditional Barbell Back Squat

ABSTRACT

Johansson, DG, Marchetti, PH, Stecyk, SD, and Flanagan, SP. A biomechanical comparison between the safety-squat bar and traditional barbell back squat. J Strength Cond Res 38(5): 825-834, 2024-The primary objectives for this investigation were to compare the kinematic and kinetic differences between performing a parallel back squat using a traditional barbell (TB) or a safety-squat bar (SSB). Fifteen healthy, recreationally trained male subjects (23 + 4 years of age) performed the back squat with a TB and an SSB at 85% of their respective 1 repetition maximum with each barbell while instrumented for biomechanical analysis. Standard inverse dynamics techniques were used to determine joint kinematic and kinetic measures. A 2 × 3 (exercise × joint) factorial analysis of variance with repeated measures was used to determine the kinetic and kinematic differences between the squats while using the different barbells. Fisher's least significant difference post hoc comparisons showed that the TB resulted in significantly greater maximum hip flexion angle (129.33 ± 11.8° vs. 122.11 ± 12.1°; p < 0.001; d = 1.80), peak hip net joint extensor torque (2.54 ± 0.4 Nm·kg -1 vs. 2.40 ± 0.4 Nm·kg -1 ; p = 0.001; d = 1.10), hip net extensor torque mechanical energy expenditure (MEE; 2.81 ± 0.5 Nm·kg -1 vs. 2.58 ± 0.6 Nm·kg -1 ; p = 0.002; d = 0.97), and ankle net joint plantar flexor torque MEE (0.32 ± 0.09 J·kg -1 vs. 0.28 ± 0.06 J·kg -1 ; p = 0.029; d = 0.63), while also lifting significantly (123.17 ± 20.8 kg vs. 117.17 ± 20.8 kg; p = 0.005; d = 0.858) more weight than the SSB. The SSB resulted in significantly higher maximum knee flexion angles (116.82 ± 5.8° vs. 115.65 ± 5.6°; p = 0.011; d = 0.75) than the TB, with no significant difference in kinetics at the knee. The TB may be preferred to the SSB for developing the hip extensors and lifting higher maximum loads. The SSB may be advantageous in situations where a more upright posture or a lower load is preferred while creating a similar demand for the knee joint.

Effects of an integrative warm-up method on the range of motion, core stability, and quality of squat performance of young adults

Introduction

This research aims to determine the effects of an integrative warm-up method on the range of motion in joints of the lower extremities, the strength of the stabilizer trunk muscles, and the quality of the basic movement patterns in older adolescents.

Methods

The study sample consisted of 88 male students (age 20.1 ± 0.5). They were randomly divided into four groups: one control group (CG) (n = 17; 180.8 ± 7.9 cm; 82.3 ± 8.3 kg) and three experimental groups (EG): EG1 (n = 23; 180.9 ± 7.0 cm; 78.5 ± 9.5 kg), EG2 (n = 31; 182.2 cm ± 7.3 cm; 79.5 ± 11.5 kg), and EG3 (n = 17; 183.3 ± 4.9 cm; 77.5 ± 11.8 kg). The participants were subjected to a 6-week experimental treatment: EG1 once, EG2 twice, and EG3 three times a week. The experimental treatment consisted of four sub-phases representing the integrative warm-up Method: 1) Inhibition (self-myofascial release using a foam roller); 2) Lengthening (Static stretching in a maximum range of motion position); 3) Activation (Positional isometrics muscle activation of the trunk and gluteus); 4) Integration (Integrated all the previous phases into one complex movement pattern). Based on the covariance analysis (ANCOVA), statistically significant treatment effects were observed and positive changes were determined in all experimental groups.

Results

The differences between groups were observed in the following variables: Overhead Squat Assessment (p = 0.000; η p 2 = 0.318 ), range of motion of left hip flexion (p = 0.000; η p 2 = 0.371 ), range of motion of right hip flexion (p = 0.000; η p 2 = 0.051 ) and range of motion of right hip extension (p = 0.051; η p 2 = 0.088 ), Double Leg Lowering Test (F = 2.411; p = 0.014; η p 2 = 0.014 ) and range of combined motion (plantar and dorsiflexion) of left ankle joint (p = 0.000; η p 2 = 0.299 ). There was no significant difference in the Plank Test (F = 1.007; p = 1.007; η p 2 = 0.035 ), range of combined motion (plantar and dorsiflexion) of right ankle joint (p = 0.088; η p 2 = 0.170 ) and range of motion of left hip extension (p = 0.158; η p 2 = 0.060 ). The participants of CG statistically significantly differed from EG1, EG2, and EG3 in the squat performance after the applied treatment.

Discussion

The effect of the treatment was the occurrence of a transformational processes in almost all measured variables. It can be concluded that the integrative method is effective and applicable in practice for both young adults and recreational athletes.

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.

Impact of squatting on selected cardiovascular parameters among college students

Squatting is an active posture test used in assessing baroreflex sensitivity, and the array of patients a physiotherapist handles may benefit from this test to avoid the adverse effects of exercise. Therefore, this study is designed to evaluate the effect of squatting on heart rate and blood pressure among undergraduate students. 35 males (mean age = 22.94 ± 1.846) and 40 females (mean age = 22.28 ± 2.075) participated in this experimental study. Demographic data and baseline cardiovascular parameters (blood pressure and heart rate) were taken before exercise. The exercise protocol, the squatting stress test, was done for 2 min, after which post-exercise blood pressure and heart rate were taken at one minute each. A repeated measure ANOVA and independent t-test were used to analyse the difference at the 0.05 alpha level. It was found that there was a significant difference between pre-exercise in lying and squatting post-exercise blood pressure and heart rate in the first and second minutes (p < 0.01), pre-exercise in lying and standing post-exercise blood pressure and heart rate in the first and second minutes (p < 0.01), pre-exercise in standing and standing post-exercise blood pressure and heart rate in the first and second minutes (p < 0.01), and pre-exercise in standing and squatting post-exercise blood pressure and heart rate in the first and second minutes (p < 0.01). Also, there was a significant difference in pre-exercise heart rate between lying and standing (p < 0.05) and not between the first minute and second minute post-squatting or standing exercise systolic blood pressure (p = 0.588) or diastolic blood pressure (p = 0.22-1). In conclusion, squatting trials among undergraduates revealed some statistically significant changes, especially between the cardiopulmonary parameters obtained in a standing position compared to lying and those measured after one minute. Therefore, caution should be observed when administering exercises that require changes in posture.

Are Diminishing Potentiation and Large Extensor Moments the Cause for the Occurrence of the Sticking Region in Maximum Free-Weight Barbell Back Squats among Resistance-Trained Males?

This study compared the kinematics, surface electromyography (sEMG) and kinetics among isometric squats performed at 10 different heights of the upward part and a one-repetition maximum (1-RM) squat. Eleven males (age: 27.5 ± 3.4 years, body mass: 84.9 ± 8.1 kg, body height: 1.79 ± 0.06 m, 1-RM squat: 152.2 ± 20.55 kg) took part in this study. It was found that force output was lowest in the sticking region at around the event of peak deceleration for the 1-RM trial with force output at 2179 ± 212 N. For the isometric trial, the lowest force output occurred at the lowest barbell height (1735 ± 299 N). In addition, for the 1-RM condition hip extension moments peaked at the first four barbell heights (6.5-6.2 Nm/kg) representing the pre-sticking and the sticking region before significantly decreasing during the events representing the post-sticking region. Additionally, the sEMG amplitude peaked for the hip extensors at the barbell heights corresponding to the post-sticking region. Moreover, the sEMG amplitude was significantly higher for the 1-RM condition for all hip extensors, vastus lateralis, and calf muscles (F ≥ 2.7, p ≤ 0.01, ηp2 ≥ 0.25). Therefore, we suggest that the sticking region occurs because of reduced force output in the pre-sticking and the sticking region in back squats among resistance-trained males. The reduced force output is probably a combination of suboptimal internal moment arms, length-tension relationships of the gluteus maximus, hamstring and vastii muscles in the pre-sticking and sticking regions to overcome the large extensor moments together with diminishing potentiation from the pre-sticking to the sticking region.

Sex differences in lower extremity kinematics during overhead and single leg squat tests

The Overhead Squat (OHS) and Single-Leg Squat (SLS) are two clinical tests used by practitioners to identify high-risk biomechanical movement patterns. Several published studies have reported sex differences in SLS performance; however, few have investigated variations during the OHS and none has measured kinematics with a marker-less motion capture system. Therefore, this study aimed to compare biomechanical movement patterns between male and female collegiate athletes during OHS and SLS testing. Seventy-five females and 58 male athletes completed OHS and SLS . A Microsoft Kinect sensor using Athletic Movement Assessment software (PhysiMax®) was used to measure kinematics. For the OHS, males displayed greater peak knee frontal plane projection angles (FPPA) (M:26°±10°, F:20°±8°; P < 0.05), peak hip flexion (M:-94°±14°, F:-87°±15°; P < 0.05), and peak trunk flexion angles (M:11°±11°, F:6°±9°; P < 0.05). For the SLS (dominant-limb), males displayed greater peak trunk flexion (M:32°±6°, F:27°±7°; P < 0.05). For the non-dominant limb, females displayed greater peak knee FPPA (F:-12°±9°, M:-8°±9°; P < 0.05) whereas males displayed greater peak trunk flexion angles (M:32°±5°, F:27°±7°; P < 0.05). These findings suggest the need for practitioners to develop sex-specific corrective exercise programmes in effort to improve lower extremity kinematics in athletes.

Kinematic variations in the barbell back squat under different footwear conditions in female college athletes

BACKGROUND

The barbell back squat is one of the most performed exercises, being important for the strengthening of lower limbs and trunk. Recently, it has become popular to train under different conditions of footwear or without it, and some investigations have analyzed the changes that this brings, with some contradictions in this regard. The purpose of this study was to analyze the kinematic variations under different shoe conditions (running shoes, barefoot and barefoot with heel raised) in the back squat in female university athletes.

METHODS

Fifteen athletes in the three conditions with a load equal to 70% of their one-maximum repetition (1RM), were recorded and analyzed to determine the angles of the ankle, knee, hip and trunk by five movements in each condition.

RESULTS

The use of enhancement significantly increased (P<0.05) the dorsal flexion angle of the ankle, against the footwear condition and barefoot without enhancement (109.6±11.1° vs. 99.1±9.0° vs. 101.3±11.5°). No significant differences were observed in any of the other variables.

CONCLUSIONS

An optimal squat technique is important for preventing injuries, optimal rehabilitation and for improving sports performance. Increased dorsal ankle flexion angle may protect distal tibiofibular joint.

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.

Different Aspects of Physical Load in Small-Sided Field Hockey Games

ABSTRACT

Wilmes, E, de Ruiter, CJ, van Leeuwen, RR, Banning, LF, van der Laan, D, and Savelsbergh, GJP. Different aspects of physical load in small-sided field hockey games. J Strength Cond Res 38(2): e56-e61, 2024-Running volumes and acceleration/deceleration load are known to vary with different formats of small-sided games (SSGs) in field hockey. However, little is known about other aspects of the physical load. Therefore, the aim of this study was to gain a more thorough understanding of the total physical load in field hockey SSGs. To that end, 2 different SSGs (small: 5 vs. 5, ∼100 m 2 per player; large: 9 vs. 9, ∼200 m 2 per player) were performed by 16 female elite field hockey athletes. A range of external physical load metrics was obtained using a global navigational satellite system and 3 wearable inertial measurement units on the thighs and pelvis. These metrics included distances covered in different velocity ranges (walk, jog, run, and sprint), mean absolute acceleration/deceleration, Hip Load, and time spent in several physically demanding body postures. The effects of SSG format on these external physical load metrics were assessed using linear mixed models ( p < 0.05). Running volumes in various speed ranges were higher for the large SSG. By contrast, mean absolute acceleration/deceleration and time spent in several demanding body postures were higher for the small SSG. This study shows that changing the SSG format affects different aspects of physical load differently.

Comparison of kinematics and electromyography in the last repetition during different maximum repetition sets in the barbell back squat

Background

The barbell squat is an exercise used to strengthen the lower limbs, with implications for both performance in sports and improving movement during everyday tasks. Although the exercise is being trained across a variety of repetition ranges, the technical requirements may vary, affecting appropriate repetition range for specific training goals.

Methods

A randomised within-subject design was used to compare kinematics and surface electromyography (EMG) in the lower extremities during different concentric phases (pre-, sticking- and post-sticking region) of the last repetition when performing squats at different repetition maximums (RMs). Thirteen strength-trained men (age: 23.6 ± 1.9 years; height: 181.1 ± 6.5 cm; body mass: 82.2 kg, 1RM: 122.8 ± 16.2, relative strength: 1.5 ± 0.2 x body mass in external load) performed a 1, 3, 6, and 10RM squat, in a randomised order.

Results

The main findings were that barbell-, ankle-, knee- and hip kinematics were similar across different repetition ranges, except for a smaller trunk lean at 1RM in the pre-sticking region compared to other repetitions and in the sticking region compared to 10RM (p ≤ 0.04). Furthermore, 1RM revealed significantly higher EMG amplitude in the vastus lateralis, gastrocnemius and soleus in the sticking and post-sticking regions when compared to 10RM. It was concluded that 10RM may locally fatigue the vastus lateralis and plantar flexors, explaining the lower EMG amplitude. The observed differences indicate that requirements vary for completing the final repetition of the 10RM compared to the 1RM, an important aspect to consider in training to enhance 1RM strength.

Support moment distribution during the back squat at different depths and loads in recreationally trained females

OBJECTIVES

The squat is used in athletic and clinical settings. However, the coordination of the lower extremity during the lift is not well understood. The purpose was to compare the peak moments of the lower extremity joints at three squat depths (above parallel, parallel and full) and three squat loads (unloaded, 50 % 1 repetition maximum, and 85 % of depth specific 1 repetition maximum) and find their contribution to support (Ms).

DESIGN

Nineteen females performed squats in a randomized order.

METHODS

Inverse dynamics and Winter's Ms equation were used to calculate peak moments of the hip, knee and ankle and calculate their contribution to Ms (α < 0.05).

RESULTS

Peak hip and ankle extensor moments varied with load but not depth and were greatest when using 85 % 1 repetition maximum. Peak knee extensor moments demonstrated a depth by load interaction. Within each depth as load increased so too did peak knee extensor moments and were highest squatting below parallel when loaded. The hip and knee contribution to Ms demonstrated a depth by load interaction while the ankle was only influenced by load. Within each depth as load increased hip contribution increased whereas the knee decreased contribution. When squatting with load the contribution of the hip decreased at below parallel while the knee increased.

CONCLUSIONS

To maximize peak hip moments squat with high load and to maximize peak knee moments squat deep with high load; however, depth and load dosages should be taken into consideration based on the status and goals of the individual.

Finding the Goldilocks Zone of Mechanical Loading: A Comprehensive Review of Mechanical Loading in the Prevention and Treatment of Knee Osteoarthritis

In this review, we discuss the interaction of mechanical factors influencing knee osteoarthritis (KOA) and post-traumatic osteoarthritis (PTOA) pathogenesis. Emphasizing the importance of mechanotransduction within inflammatory responses, we discuss its capacity for being utilized and harnessed within the context of prevention and rehabilitation of osteoarthritis (OA). Additionally, we introduce a discussion on the Goldilocks zone, which describes the necessity of maintaining a balance of adequate, but not excessive mechanical loading to maintain proper knee joint health. Expanding beyond these, we synthesize findings from current literature that explore the biomechanical loading of various rehabilitation exercises, in hopes of aiding future recommendations for physicians managing KOA and PTOA and athletic training staff strategically planning athlete loads to mitigate the risk of joint injury. The integration of these concepts provides a multifactorial analysis of the contributing factors of KOA and PTOA, in order to spur further research and illuminate the potential of utilizing the body's own physiological responses to mechanical stimuli in the management of OA.

The effect of experimentally induced gluteal muscle weakness on joint kinematics, reaction forces, and dynamic balance performance during deep bilateral squats

Squatting is a common daily activity and fundamental exercise in resistance training and closed kinetic chain programs. The aim of this study was to investigate the effects of an experimentally induced weakness of the gluteal muscles on joint kinematics, reactions forces (JRFs), and dynamic balance performance during deep bilateral squats in healthy young adults. Ten healthy adults received sequential blocks of (1) branch of the superior gluteal nerve to the tensor fasciae latae (SGNtfl) muscle, (2) superior gluteal nerve (SGN), and (3) inferior gluteal nerve (IGN) on the dominant right leg. At the control condition and following each block, the participants were instructed to perform deep bilateral squats standing on two force plates. Hip, knee, ankle, and pelvis kinematics did not differ significantly following iatrogenic weakness of gluteal muscles. The most important finding was the significant differences in JRFs following SGN and IGN block, with the affected hip, patellofemoral, and ankle joint demonstrating lower JRFs, whereas the contralateral joints demonstrated significantly higher JRFs, especially the patellofemoral joint which demonstrated an average maximum difference of 1.43 x body weight compared with the control condition. When performing a deep bilateral leg squat under SGN and IGN block, the subjects demonstrated an increased center of pressure (CoP) range and standard deviation (SD) in mediolateral compared with the control condition. These results imply that squat performance changes significantly following weakness of gluteal muscles and should be considered when assessing and training athletes or patients with these injuries.

Optimizing Resistance Training Technique to Maximize Muscle Hypertrophy: A Narrative Review

Regimented resistance training (RT) has been shown to promote increases in muscle size. When engaging in RT, practitioners often emphasize the importance of appropriate exercise technique, especially when trying to maximize training adaptations (e.g., hypertrophy). This narrative review aims to synthesize existing evidence on what constitutes proper RT exercise technique for maximizing muscle hypertrophy, focusing on variables such as exercise-specific kinematics, contraction type, repetition tempo, and range of motion (ROM). We recommend that when trying to maximize hypertrophy, one should employ a ROM that emphasizes training at long muscle lengths while also employing a repetition tempo between 2 and 8 s. More research is needed to determine whether manipulating the duration of either the eccentric or concentric phase further enhances hypertrophy. Guidelines for body positioning and movement patterns are generally based on implied theory from applied anatomy and biomechanics. However, existing research on the impact of manipulating these aspects of exercise technique and their effect on hypertrophy is limited; it is therefore suggested that universal exercise-specific kinematic guidelines are followed and adopted in accordance with the above recommendations. Future research should investigate the impact of stricter versus more lenient exercise technique variations on hypertrophy.

Evaluation of balance in patients with systemic sclerosis

BACKGROUND

The aim was to examine static/dynamic balance and proprioception of Systemic Sclerosis by comparing healthy and relationship with demographic and disease-related data.

METHODS

21 Systemic Sclerosis and 19 healthy were included.Berg Balance Scale (functional balance), Sensamove Sensbalance Maxiboard Software (static, dynamic balance:reaction time and travel time and proprioception), Scleroderma Health Assessment Questionnaire/Health Assessment Questionnaire (health status), Medsger's Disease Severity Scale, Modified Rodnan Skin Score were used in evaluation.

FINDINGS

Comparing the groups, there was significant difference in Berg Balance Scale (p:0.036); Health Assessment Questionnaire/Scleroderma Health Assessment Questionnaire (p:0.001); Static balance-center (p:0.001), front (p:0.001), back (p:0.001), left (p:0.001), right (p:0.021); proprioception-front (p:0.025);Reaction Time-front (p:0.031) and left (p:0.010);Travel Time-front (p:0.041) and left (p:0.014) in favor of healthy group.In Systemic Sclerosis, disease severity had moderate correlation with static balance-back (r:-0.504,p:0.020).Skin thickness had low correlation with Reaction Time-front (r:-0.449,p:0.041).Age had low correlation with Travel time-front (r:0.458,p:0.037) and proprioception-left (r:0.450,p:0.041); moderate with Travel time-back (r:0.515;p:0.017) and proprioception-front (r:0.539,p:0.012).

INTERPRETATION

Compared to healthy, Systemic Sclerosis had worse health status, functional balance, static/dynamic balance and proprioception.This situation is related to disease severity, skin thickness and age. Evaluations made with objective methods may have the potential to determine the extent of the problem.Clinicians can guide the treatment of patients with SSc by evaluating their static/dynamic balance and proprioception.With early treatment, additional problems that may occur due to worsening of balance and proprioception can be prevented.Proprioception and dynamic balance evaluation can be performed for older patients, static balance when disease activity is high, and dynamic balance when skin thickness score is high.

Sagittal trunk excursion and lumbar repositioning error between female and male patients with patellofemoral pain syndrome

Background

Patellofemoral pain syndrome (PFPS) is a challenging clinical problem affecting adults, adolescents, and physically active populations. PFPS impacts the patient's trunk kinematics in the frontal plane. Previous studies have found gender-based biomechanical differences in patients with PFPS; however, sagittal trunk kinematics during mini-squats and lumbar proprioception in PFPS have not been studied previously.

Objectives

To investigate sagittal trunk excursion (It is defined as the sagittal trunk flexion angle from the start to the end of the mini squat) during mini-squats as well as lumbar repositioning error between individuals with and without PFPS, and determine gender differences in the outcome variables.

Methods

A sample of 56 participants aged 18-25 years was enrolled; 30 with PFPS (13 males, 17 females) and 26 asymptomatic controls (11 males, 15 females). The sagittal trunk excursion during mini-squats was examined by two-dimensional (2D) photographic analysis using Surgimap software. Active lumbar flexion repositioning error was assessed using an isokinetic dynamometer.

Results

For sagittal trunk excursion, no significant main effect of group was observed (p = 0 . 136 ). On the other hand, the main effect was significant for gender (p = 0 . 005 ), as was the interaction effect. Compared to the control group, the PFPS group showed significantly (p = 0 . 01 ) lower sagittal trunk excursion in females than in males during mini-squats. For active lumbar flexion repositioning error, no evidence was found for significant main or interaction effects (p > 0 . 05 ).

Conclusion

Females with PFPS exhibit a more erect sagittal trunk posture than males during mini-squats. Trunk posture should be considered during weight-bearing activities in PFPS, and gender-specific assessment protocols should be developed.

The effects of fatigue on linear and angular kinematics during bilateral squat

This study was aimed to analyze in detail how the fatigue effects to kinematic parameters of body weight squat exercise (BSQ) by dividing a squat cycle into four different regions. Twenty-one male athletes participated in this study. Participants were divided into two groups according to their lower limb muscle ratio (LLMR). The BSQ was performed until participants were unable to continue the exercise due to the fatigue. Linear and angular kinematics were obtained by motion analysis software which has high validity and reliability. There was no significant but had large effect size interaction between fatigue conditions and LLMR groups in terms of knee ROM in the extension phase and hip angular velocity in braking phase of the flexion (0.08 > p >0.05, 0.18 > [Formula: see text] > 0.16). Fatigue condition did not have a significant effect on the duration in the acceleration and braking phases of BSQ (p > 0.05). There were many significant main effects on kinematics in the different regions due to the fatigue (0.01 < p <0.05, 0.44 > [Formula: see text] > 0.14). In the fatigue condition, there was a polynomial relationship between velocity of shoulder and hip joints (R2flex = 0.82, R2ext = 0.72) rather than linear (R2flex = 0.64, R2ext = 0.53) and coefficient correlations also decreased (rflex = 0.88 to 0.80, rext = 0.92 to 0.73). The sticking region was observed in the non-fatigue condition and disappeared when fatigue occurred. These results suggest that LLMR may be taken into consideration in the squat exercises, joint tracking may vary for velocity-based squat training and pre-test for sticking region observation may be apply with the BSQ.

New training load metrics in field hockey using inertial measurement units

Field hockey players are exposed to high biomechanical loads. These loads often cannot be adequately estimated with global navigational satellite systems (GNSS) since on-field displacements during these movements are often small. Therefore, this study aims to explore the potential of different proxies of biomechanical load in field hockey with use of a simple inertial measurement unit (IMU) system. Sixteen field hockey players performed a range of field hockey specific exercises, including running with stick on the ground, running upright, and different types of shots and passes. All exercises were performed at two different frequencies (i.e. number of actions per minute). A variety of proxies of biomechanical load (time spent with forward tilted pelvis, time spent in lunge position, time spent with flexed thighs, and Hip Load) were obtained using wearable IMUs. In addition, total distance was quantified using a GNSS system. Linear mixed models were constructed to determine the effects of the different exercises and action frequency on all quantified metrics. All metrics increased approximately proportional to the increase in action frequency. Total distance and Hip Load were greatest for the running exercises, but the different types of shots and passes had greater effects on specific on the times spent in the demanding body postures. This shows that these proxies of biomechanical load can be used to estimate field hockey-specific biomechanical loads. The use of these metrics may provide coaches and medical staff with a more complete view of the training load that field hockey players experience.Highlights New proxies of biomechanical load derived with inertial measurement units were used to quantify field hockey specific biomechanical loads.These new biomechanical metrics are complementary to metrics obtained with global navigation satellite systems and increased proportionally to a doubling of the exercise intensity.The presented biomechanical load metrics can help field hockey coaches to achieve a better balance between load and recovery for their players.

The interrelationship between lower limb movement, muscle activity, and joint moment during half squat and gait

Joint moment is the resultant force of limb movements. However, estimation methods for joint moments using surface electromyography frequently use joint angles instead of limb angles. The limb angle in joint moment estimation using electromyography could clarify the effects of muscle activity on the limbs: acceleration, deceleration, or stabilization. No study has quantified the comprehensive relationship between limb movement, muscle activity, and joint moment. This study aimed to determine the influencing factors for ankle-joint moment and knee-joint moment in the sagittal plane among muscle activities and parameters related to limb movements during half squat and gait. This study included 29 healthy adults (16 female participants, 21.1 ± 2.09 years). Using inertial measurement units, thigh, shank, and foot inclination angles and angular accelerations were calculated as the parameters of limb movements. Muscle activations of the biceps femoris long head, rectus femoris, gastrocnemius, and tibialis anterior were measured. Ankle joint moment and knee-joint moment were measured using a three-dimensional motion capture system and two force plates. Regression models showed high accuracy in measuring ankle-joint moment during a half squat and gait (R2f = 0.92, 0.97, respectively) and knee-joint moment during a half squat (R2f = 0.98), but not knee-joint moment during gait (R2f = 0.63). However, only a maximum of five parameters were selected from muscle activities and limb angular information. Tibialis anterior and gastrocnemius activity were the largest contributors to ankle-joint moment during a half squat and gait, respectively, while muscle activities were not directly reflected in the knee-joint moment during either movement. Consideration of the interrelationships among limb movement, muscle activity, and joint moment is required when adjusting joint movements according to the target and aim of the therapeutic interventions.

Individual Muscle Contributions to the Acceleration of the Center of Mass During the Barbell Back Squat in Trained Female Subjects

ABSTRACT

Goodman, WW, Helms, E, and Graham, DF. Individual muscle contributions to the acceleration of the center of mass during the barbell back squat in trained female subjects. J Strength Cond Res 37(10): 1947-1954, 2023-The squat is used to enhance performance and rehabilitate the lower body. However, muscle forces and how muscles accelerate the center of mass (CoM) are not well understood. The purpose was to determine how lower extremity muscles contribute to the vertical acceleration of the CoM when squatting to parallel using 85% one-repetition maximum. Thirteen female subjects performed squats in a randomized fashion. Musculoskeletal modeling was used to obtain muscle forces and muscle-induced accelerations. The vasti, soleus, and gluteus maximus generated the largest upward accelerations of the CoM, whereas the muscles that produced the largest downward acceleration about the CoM were the hamstrings, iliopsoas, adductors, and tibialis anterior. Our findings indicate that a muscle's function is task and posture specific. That is, muscle function depends on both joint position and how an individual is interacting with the environment.

Backseat Inclination Affects the Myoelectric Activation During the Inclined Leg Press Exercise in Recreationally Trained Men

ABSTRACT

Marchetti, PH, Gomes, WA, Da Silva, JJ, Magalhaes, RA, Teixeira, LFM, and Whiting, WC. Backseat inclination affects the myoelectric activation during the inclined leg press exercise in recreationally trained men. J Strength Cond Res 37(10): e541-e545, 2023-Changes in the angle between the seat and backrest during the inclined leg press (ILP) exercise may influence myoelectric activity. The purpose of this study was to evaluate the myoelectric activity between 2 different angles between the seat and backrest (90° and 125°) during the ILP exercise in recreationally trained men. Fifteen young, resistance-trained men (age: 26.8 ± 5.3 years, height: 173.8 ± 6.6 cm, total body mass: 81.6 ± 7.6 kg) performed 1 set of 10 repetitions at 70% of their body mass during the ILP exercise using 2 different angles between the seat and backrest (ILP90° and ILP125°). Surface electromyography (peak RMS 90 and iEMG) was used to measure the myoelectric activity of the vastus lateralis (VL), biceps femoris (BF), and gluteus maximus (GM). A paired t test was used to measure differences in knee and hip joint displacement, peak RMS 90 , and iEMG between ILP90 and ILP125. The hip angle presented a greater displacement during the ILP125 when compared with ILP90 ( p < 0.001), considering a similar knee joint displacement. For the VL, there was observed greater myoelectric activation (peak RMS 90 and iEMG) during ILP125 when compared with ILP90 ( p < 0.05). For the BF, there was observed greater myoelectric activation (peak RMS 90 and iEMG) during ILP90 when compared with ILP125 ( p < 0.05). However, GM did not present differences between ILP90 and ILP125. In conclusion, the angle between the seat and backrest (ILP90 or ILP125) altered the myoelectric activation of the VL and BF with no difference for the GM.

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).

The Effect of Volitional Preemptive Abdominal Contraction on Biomechanical Measures During A Front Versus Back Loaded Barbell Squat

Background

Weightlifting is growing in popularity among recreational and competitive athletes. The barbell back squat (BackS) is commonly included in these training programs, while the barbell front squat (FrontS) is commonly performed as a component of other lifts such as the power clean or clean and jerk, it is less commonly practiced in isolation.

Hypothesis/Purpose

The purpose of this study was to examine the effects of VPAC performance on trunk muscle and LE biomechanical responses during loaded BackS versus FrontS in healthy subjects.

Study Design

Controlled Laboratory Study.

Methods

Healthy male subjects with the ability to perform a sub-maximal loaded barbell squat lift were recruited. Subjects completed informed consent, demographic/medical history questionnaires and an instructional video. Subjects practiced VPAC and received feedback. Surface electromyography (sEMG) electrodes and kinematic markers were applied. Muscles included were the internal oblique (IO), external oblique (EO), rectus abdominis, iliocostalis lumborum (ICL), superficial multifidi, rectus femoris, vastus lateralis, biceps femoris, and gluteus maximus. Maximal voluntary isometric contractions established reference sEMG values. A squat one-rep-max (1RM) was predicted by researchers using a three to five repetition maximum (3RM, 5RM) load protocol. Subjects performed BackS trials at 75% 1RM while FrontS trials were performed at 75% BackS weight, both with and without VPAC. Subjects performed three repetitions of each condition with feet positioned on two adjacent force plates. Significant interactions and main effects were tested using a 2(VPAC strategy) x 2(squat variation) and 2(VPAC strategy) x 2(direction) within-subject repeated measures ANOVAs. Tukey's Post-Hoc tests identified the location of significant differences.

Results

Trunk muscle activity was significantly higher during FrontS versus BackS regardless of VPAC condition. (IO: p=0.018, EO: p<0.001, ICL: p<0.001) VPAC increased performance time for both squat variations (p=.0011), which may be associated with decreased detrimental force potential on the lumbar spine and knees. VPAC led to improved ability to maintain a neutral lumbar spine during both squat variations. This finding is associated with decreased detrimental force potential on the lumbar spine.

Conclusions

Findings could help guide practitioners and coaches to choose squat variations and incorporate VPAC strategies during their treatments and/or training programs.

Level of Evidence

Level 3©The Author(s).