The influence of different footwear on 3-D kinematics and muscle activation during the barbell back squat in males

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.

Textile electromyography electrodes reveal differences in lower limb muscle activation during loaded squats when comparing fixed and free barbell movement paths

INTRODUCTION

Traditional recordings of muscle activation often involve time-consuming application of surface electrodes affixed to the skin in laboratory environments. The development of textile electromyography (EMG) electrodes now allows fast and unobtrusive assessment of muscle activation in ecologically valid environments. In this study, textile EMG shorts were used to assess whether performing squats with the barbell resting freely on the shoulders or using a Smith machine for a fixed barbell movement path is preferable for maximizing lower limb muscle activation.

METHODS

Sixteen athletes performed free and fixed barbell squats in a gym with external loads equivalent to their body mass. Quadriceps, hamstrings and gluteus maximus activation was measured bilaterally with textile EMG electrodes embedded in shorts.

RESULTS

Mean quadriceps activation was greater for the free compared with the fixed movement path for the right (mean difference [MD] 14μV, p = 0.04, ηp 2 = 0.28) and left leg (MD 15μV, p = 0.01, ηp 2 = 0.39) over the entire squat and specifically during the first half of the eccentric phase for the left leg (MD 7μV, p = 0.04, d = 0.56), second half of the eccentric phase for both legs (right leg MD 21μV, p = 0.05, d = 0.54; left leg MD 23μV, p = 0.04, d = 0.52) and the first half of the concentric phase for both legs (right leg MD 24μV, p = 0.04, d = 0.56; left leg MD 15μV, p = 0.01, d = 0.72). Greater hamstrings activation for the free path was seen for the second half of the eccentric phase (left leg MD 4μV, p = 0.03, d = 0.58) and first half of the concentric phase (right leg MD 5μV, p = 0.02, d = 0.72). No significant differences were found for gluteus maximus.

DISCUSSION

Textile EMG electrodes embedded in shorts revealed that to maximize thigh muscle activity during loaded squats, a free barbell movement path is preferable to a fixed barbell movement path.

Two-Experiment Examination of Habitual and Manipulated Foot Placement Angles on the Kinetics, Kinematics, and Muscle Forces of the Barbell Back Squat in Male Lifters

This two-experiment study aimed to examine the effects of different habitual foot placement angles and also the effects of manipulating the foot placement angle on the kinetics, three-dimensional kinematics and muscle forces of the squat. In experiment 1, seventy lifters completed squats at 70% of their one repetition maximum using a self-preferred placement angle. They were separated based on their habitual foot angle into three groups HIGH, MEDIUM and LOW. In experiment 2, twenty lifters performed squats using the same relative mass in four different foot placement angle conditions (0°, 21°, 42° and control). Three-dimensional kinematics were measured using an eight-camera motion analysis system, ground reaction forces (GRF) using a force platform, and muscle forces using musculoskeletal modelling techniques. In experiment 1, the impulse of the medial GRF, in the descent and ascent phases, was significantly greater in the HIGH group compared to LOW, and in experiment 2 statistically greater in the 42° compared to the 21°, 0° and control conditions. Experiment 2 showed that the control condition statistically increased quadriceps muscle forces in relation to 0°, whereas the 0° condition significantly enhanced gluteus maximus, gastrocnemius and soleus forces compared to control. In experiment 1, patellofemoral joint stress was significantly greater in the HIGH group compared to LOW, and in experiment 2, patellar and patellofemoral loading were statistically greater in the control compared to the 42°, 21°, 0° and control conditions. Owing to the greater medial GRF's, increased foot placement angles may improve physical preparedness for sprint performance and rapid changes of direction. Reducing the foot angle may attenuate the biomechanical mechanisms linked to the aetiology of knee pathologies and to promote gluteus maximus, gastrocnemius and soleus muscular development. As such, though there does not appear to be an optimal foot placement angle, the observations from this study can be utilised by both strength and conditioning and sports therapy practitioners seeking to maximise training and rehabilitative adaptations.

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.

Effect of rearfoot valgus on biomechanics during barbell squatting: A study based on OpenSim musculoskeletal modeling

Background

Barbell squats are commonly used in daily training and rehabilitation. Injuries are not common when the posture is standard, but the wrong posture can lead to injuries. Rearfoot valgus is a common foot abnormality that may increase the risk of injury during sports. The purpose of this study was to compare the biomechanics of lower limbs in normal foot and valgus patients during barbell squat.

Methods

In this study, 10 participants with normal foot shape and 10 participants with rearfoot valgus were enrolled. The joint angle, joint moment, and range of motion of hip, knee, and ankle joints were collected under 0, 30, and 70% one-repetition maximum (RM) load, where discrete data are statistically analyzed using the independent sample t-test, and continuous data are statistically analyzed using one-dimensional parameter statistical mapping.

Results

In barbell squats, the range of motion and the joint moment of the hip, knee, and ankle in the rearfoot valgus participants were significantly larger than those in normal foot participants (p < 0.05). The participants with rearfoot valgus had a more significant knee valgus angle when squatting to the deepest (p < 0.05). In addition, with the increase in load, the participants with rearfoot valgus showed greater standardized medial knee contact force (p < 0.05). In the process of barbell squats, the participants with rearfoot valgus showed no significant difference in the foot valgus angle when compared with the normal foot shape (p > 0.05).

Conclusions

The valgus population showed a greater range of joint motion when performing barbell squats and showed genu valgus and greater medial knee contact force, which may increase the risk of musculoskeletal and soft tissue damage such as meniscus wear. In addition, there was no significant difference in the rearfoot valgus angle between people with rearfoot valgus and people with normal foot shape during squatting, so barbell squatting may correct valgus to a certain extent.

Effect of Heel Lift Insoles on Lower Extremity Muscle Activation and Joint Work during Barbell Squats

The effect of heel elevation on the barbell squat remains controversial, and further exploration of muscle activity might help find additional evidence. Therefore, 20 healthy adult participants (10 males and 10 females) were recruited for this study to analyze the effects of heel height on lower extremity kinematics, kinetics, and muscle activity using the OpenSim individualized musculoskeletal model. One-way repeated measures ANOVA was used for statistical analysis. The results showed that when the heel was raised, the participant’s ankle dorsiflexion angle significantly decreased, and the percentage of ankle work was increased (p < 0.05). In addition, there was a significant increase in activation of the vastus lateralis, biceps femoris, and gastrocnemius muscles and a decrease in muscle activation of the anterior tibialis muscle (p < 0.05). An increase in knee moments and work done and a reduction in hip work were observed in male subjects (p < 0.05). In conclusion, heel raises affect lower extremity kinematics and kinetics during the barbell squat and alter the distribution of muscle activation and biomechanical loading of the joints in the lower extremity of participants to some extent, and there were gender differences in the results.

The impact of foot angle on lower limb muscles activity during the back squat and counter movement jump

BACKGROUND

Squatting is a core exercise for many purposes. However, there is still controversy surrounding the practice of targeting specific muscle groups when performing the back squat with different stance widths or foot positions. Therefore, this study aimed to assess lower limb muscle activation during different form of back squat when adopting three different foot angles.

METHODS

Eight male active participants (age 24.0±0.8 years, height 1.80±0.63m and mass 85.8±8.7kg) performed maximal isometric squat, back squat with an overalod of 80% of 1 repetition maximum, and countermovement jump (CMJ) when adopting three foot rotation angles: parallel (0°); +10° outward (external rotation); +20° outward (external rotation). We calculated the root mean square of the electromyographic signals recorded from eight participant's dominant leg muscles.

RESULTS

During the descending phase of the back squat, the 20° external foot rotation elicited greater activation of the biceps femoris (+35%; p = 0.027) and gastrocnemius medialis (+70%; p = 0.040) compared to parallel foot. There were no significant differences among the other muscles and exercise conditions.

CONCLUSIONS

The +20° foot position increased BF and GasM muscle activity only during the downward phase of the back squat. Strength coaches should consider the present findings when selecting specific resistance exercises aiming to improve athletes' strength and physical fitness.

Footwear and Elevated Heel Influence on Barbell Back Squat: A Review

The back squat is one of the most effective exercises in strengthening the muscles of the lower extremity. Understanding the impact of footwear has on the biomechanics is imperative for maximizing the exercise training potential, preventing injury, and rehabilitating from injury. This review focuses on how different types of footwear affect the full-body kinematics, joint loads, muscle activity, and ground reaction forces in athletes of varying experience performing the weighted back squat. The literature search was conducted using three databases, and fourteen full-text articles were ultimately included in the review. The majority of these studies demonstrated that the choice of footwear directly impacts kinematics and kinetics. Weightlifting shoes were shown to decrease trunk lean and generate more plantarflexion relative to running shoes and barefoot lifting. Elevating the heel through the use of external squat wedges is popular method during rehabilitation and was shown to provide similar effects to weightlifting shoes. Additional research with a broader array of populations, particularly novice and female weightlifters, should be conducted to generalize the research results to nonathlete populations. Further work is also needed to characterize the specific effects of sole stiffness and heel elevation height on squatting mechanics.

Effect of Footwear on the Biomechanics of Loaded Back Squats to Volitional Exhaustion in Skilled Lifters

ABSTRACT

Brice, SM, Doma, K, and Spratford, W. Effect of footwear on the biomechanics of loaded back squats to volitional exhaustion in skilled lifters. J Strength Cond Res XX(X): 000-000, 2021-This study examined whether footwear influences the movement dynamics of barbell back squats to volitional exhaustion in experienced lifters. Eleven men (1 repetition maximum [1RM] = 138 ± 19 kg; 1RM % body mass = 168 ± 18%) performed 3 sets (5-12 ± 4 repetitions per set) of loaded barbell back squats to volitional exhaustion using raised-heel and flat-heel footwear. Barbell motion as well as moments, angles, angular velocity, and power in the sagittal plane at the ankle, knee, hip, and lumbopelvis were examined during the second repetition of the first set (Tsecond) and the final repetition of the third set (Tfinal). There were significant reductions (p < 0.05) in lower-limb concentric angular velocity and power output for both footwear conditions. For the raised-heel condition at Tfinal, hip and knee concentric angular velocities were significantly slower (p < 0.05), and knee concentric power output was significantly less (p < 0.05) compared with the flat-heel condition. A reduction in barbell velocity was not observed for the raised-heel condition despite there being reduction in hip and knee angular velocities. Furthermore, no differences were identified in lower-limb joint moments or any of the biomechanical characteristics of the lumbopelvis between the footwear conditions. The findings of this study suggest that neither type of footwear reduced joint loading or improved joint range-of-motion.

The effect of elevating the heels on spinal kinematics and kinetics during the back squat in trained and novice weight trainers

This research assessed the influence of various heel elevation conditions on spinal kinematic and kinetic data during loaded (25% and 50% of body weight) high-bar back squats. Ten novice (mass 67.6 ± 12.4 kg, height 1.73 ± 0.10 m) and ten regular weight trainers (mass 66.0 ± 10.7 kg, height 1.71 ± 0.09 m) completed eight repetitions at each load wearing conventional training shoes standing on the flat level floor (LF) and on an inclined board (EH). The regular weight training group performed an additional eight repetitions wearing weightlifting shoes (WS). Statistical parametric mapping (SPM1D) and repeated measures analysis of variance were used to assess differences in spinal curvature and kinetics across the shoe/floor conditions and loads. SPM1D analyses indicated that during the LF condition the novice weight trainers had greater moments around L4/L5 than the regular weight trainers during the last 20% of the lift (P < 0.05), with this difference becoming non-significant during the EH condition. This study indicates that from a perspective of spinal safety, it appears advantageous for novice weight trainers to perform back squats with their heels slightly elevated, while regular weight trainers appear to realize only limited benefits performing back squats with either EH or WS.

Heel-Raised Foot Posture Does Not Affect Trunk and Lower Extremity Biomechanics During a Barbell Back Squat in Recreational Weight lifters

Lee, S-P, Gillis, CB, Ibarra, JJ, Oldroyd, DF, and Zane, RS. Heel-raised foot posture does not affect trunk and lower extremity biomechanics during a barbell back squat in recreational weight lifters. J Strength Cond Res 33(3): 606-614, 2019-It is claimed that weightlifting shoes with a raised heel may lead to a more upright trunk posture, and thus reduce the risk of back injuries during a barbell back squat. These proclaimed biomechanical effects have not been thoroughly investigated. The purpose of this study was to compare trunk and lower extremity biomechanics during barbell back squats in three foot postures. Fourteen recreational weight lifters (7 men and 7 women) between the ages of 18 and 50 years performed barbell back squats in three conditions (barefoot on a flat surface, barefoot on a heel-raised platform, and wearing heel-raised weightlifting shoes) at 80% of their 1 repetition maximum. Surface electromyography was used to assess the activation of the knee extensors and paraspinal muscles at L3 and T12 spinal levels. A 3D motion capture system and an electrogoniometer recorded the kinematics of the thoracic spine, lumbar spine, and knee during the back squat to a depth where the hip was at least at the same level to the knee. Results indicated that none of the heel-raised foot postures significantly affected trunk and lower extremity muscle activation (thoracolumbar paraspinal [p = 0.52], lumbar paraspinal [p = 0.179], knee extensor [p = 0.507]) or the trunk angles (thoracolumbar spine [p = 0.348], lumbar spine [p = 0.283]) during the squat. Our results demonstrated that during barbell back squats, heel-raised foot postures do not significantly affect spinal and knee extensor muscle activations, and trunk and knee kinematics. Heel-raised weightlifting shoes are unlikely to provide significant protection against back injuries for recreational weight lifters during the barbell back squat.

A Review of the Biomechanical Differences Between the High-Bar and Low-Bar Back-Squat

Glassbrook, DJ, Helms, ER, Brown, SR, and Storey, AG. A review of the biomechanical differences between the high-bar and low-bar back-squat. J Strength Cond Res 31(9): 2618-2634, 2017-The back-squat is a common exercise in strength and conditioning for a variety of sports. It is widely regarded as a fundamental movement to increase and measure lower-body and trunk function, as well as an effective injury rehabilitation exercise. There are typically 2 different bar positions used when performing the back-squat: the traditional "high-bar" back-squat (HBBS) and the "low-bar" back-squat (LBBS). Different movement strategies are used to ensure that the center of mass remains in the base of support for balance during the execution of these lifts. These movement strategies manifest as differences in (a) joint angles, (b) vertical ground reaction forces, and (c) the activity of key muscles. This review showed that the HBBS is characterized by greater knee flexion, lesser hip flexion, a more upright torso, and a deeper squat. The LBBS is characterized by greater hip flexion and, therefore, a greater forward lean. However, there are limited differences in vertical ground reaction forces between the HBBS and LBBS. The LBBS can also be characterized by a greater muscle activity of the erector spinae, adductors, and gluteal muscles, whereas the HBBS can be characterized by greater quadriceps muscle activity. Practitioners seeking to develop the posterior-chain hip musculature (i.e., gluteal, hamstring, and erector muscle groups) may seek to use the LBBS. In comparison, those seeking to replicate movements with a more upright torso and contribution from the quadriceps may rather seek to use the HBBS in training.