Squat Performance Research Articles

The Acute Impact of External Compression on Back Squat Performance in Competitive Athletes.

The aim of the present study was to evaluate the effects of external compression with blood flow restriction on power output and bar velocity changes during the back-squat exercise (SQ). The study included 10 judo athletes (age = 28.4 ± 5.8 years; body mass = 81.3 ± 13.1 kg; SQ one-repetition maximum (1-RM) 152 ± 34 kg; training experience 10.7 ± 2.3 years). Methods: The experiment was performed following a randomized crossover design, where each participant performed three different exercise protocols: (1) control, without external compression (CONT); (2) intermittent external compression with pressure of 100% arterial occlusion pressure (AOP) (EC-100); and (3) intermittent external compression with pressure of 150% AOP (EC-150). To assess the differences between conditions, the participants performed 3 sets of 3 repetitions of the SQ at 70% 1-RM. The differences in peak power output (PP), mean power output (MP), peak bar velocity (PV), and mean bar velocity (MV) between the three conditions were examined using repeated measures two-way ANOVA. Results: The post hoc analysis for the main effect of conditions showed a significant increase in PP (p = 0.03), PV (p = 0.02), MP (p = 0.04), and MV (p = 0.03), for the EC-150, compared to the CONT. Furthermore, a statistically significant increase in PP (p = 0.04), PV (p = 0.03), MP (p = 0.02), and MV (p = 0.01) were observed for the EC-150 compared to EC-100. There were no significant changes in PP, PV, MP, and MV, between EC-100 and CONT conditions. Conclusion: The results indicate that the use of extremely high-pressure external compression (150% AOP) during high-loaded (70% 1-RM) lower limb resistance exercise elicits an acute increase in power output and bar velocity.

Effects of Visual Feedback Complexity on the Performance of a Movement Task for Rehabilitation

This study investigated the effects of visual feedback (VF) complexity on movement performance to potentially optimize the design of VF-based rehabilitation. We evaluated the effects of VF complexity on performance of the two-legged squat during training with concurrent (real-time) VF and short-term retention with no VF. Four VF cases were employed to train spatial positioning of the thigh segment in unique combinations of complexity (simple, complex) and representation of body-discernibility (abstract, representative). Eighteen able-bodied subjects attempted to minimize the error between individual body segment positions and a target trajectory during concurrent VF and short-term retention tests. Complex-representative VF demonstrated greater potential for training with increased performance consistency in both motion and muscle activity patterns.

The Effects of Protein and Carbohydrate Supplementation on Muscular Regeneration After Intense Resistance Training in Soccer Players

Abstract Objectives Nutrition is a key element in post-exercise regeneration. Various studies suggest that ingestion of combined carbohydrates and proteins after exercise result in a decrease of inflammatory processes and consequently in an increase of regeneration and physical performance. Recent studies compared the pro-regenerative effects of protein/carbohydrate shakes with the intake of foodstuffs (white bread and high protein cheese) on the skeletal muscle after acute endurance exercise. The aim of this study was to evaluate the influence of a conventional curd/juice shake on the regenerative capacity of soccer players after intensive strength training. Methods Therefore, sixteen young healthy in-season football payers run through a placebo checked double-blind crossover study with two groups. After a standardized training protocol, 3 sets of 12 reps deep back squats and 3 sets of 15 reps drop jumps, the participants ingested either a placebo shake (placebo-group, total calories < 10 kcal) or a conventional shake of 300 g curd and 200 ml grape juice (protein 35.8 g, carbohydrates 43.6 g, fat 0.9 g, total calories 338 kcal). To evaluate the muscle damage effects, serum creatin kinase (CK) as a physiological parameter as well 10 m sprint, counter movement jump (CMJ) and 3RM-squat as functional markers were measured at two time points (t0, t24). In addition, the CK of five players was analysed after a soccer match. Results The results show a positive trend concerning sprint and squat performance in the shake group. Especially in the squat group a significant decrease of performance was observed in the placebo group compared to the shake group (PL: −5.0 kg, P ≤ 05, SH: −3,2 kg, P = .10). In CMJ and CK no difference was observed between the two groups. In both groups, the jump in CMJ decreased and the CK value increased significantly. The increase in CK due to intensive resistance training is also comparable to the muscle damage after a football match. Conclusions In summary, it was found that a quark/juice shake has a positive influence on strength performance in soccer players after intensive strength training. These findings confirm observations from previous studies. However, the positive effects on CK could not be observed in this study. Therefore, further research on conventional foodstuff after resistance training is necessary. Funding Sources No funding.

Real-time visual feedback reduces patellofemoral joint forces during squatting in individuals with patellofemoral pain

BackgroundElevated patellofemoral joint forces appear to contribute to the development of patellofemoral pain. As a result, treatment of patellofemoral pain often includes movement retraining intended to reduce patellofemoral joint forces. Real-time visual feedback has been shown to be effective for retraining running kinematics; however, we are not aware of a previous study that has examined the influence of real-time visual feedback on patellofemoral joint mechanics during a squat. MethodsTwenty individuals with patellofemoral pain completed squats before (baseline) and immediately after (post-feedback) completing a real-time visual feedback training session. During the session, participants received visual feedback related to their patellofemoral joint forces (estimated via a musculoskeletal model) during squatting and were asked to alter their movement pattern to minimize these forces. Patellofemoral joint forces and hip, knee, and ankle joint mechanics were compared for the baseline and post-feedback trials in order to examine how feedback influenced squat performance. FindingsParticipants demonstrated a 14.4% reduction in patellofemoral joint forces following the feedback session. They appeared to achieve this reduction in patellofemoral joint forces by squatting with less knee flexion (97.26 ± 17.11° vs. 102.96 ± 16.55°) and lower knee extension moments (0.10 ± 0.02 Nm/bodyweight vs. 0.11 ± 0.02 Nm/bodyweight) and quadriceps forces (4.06 ± 0.87 bodyweights vs. 4.67 ± 0.98 bodyweights). InterpretationReal-time visual feedback appears to be effective for reducing patellofemoral joint forces during squatting in individuals with patellofemoral pain. As a result, training of this nature may be beneficial when treating patellofemoral pain.

Single-Leg Squat Performance and Reported Pain within Youth Softball Players

The purpose of this study was to assess single-leg squat (SLS) performance on reported pain. Forty-two youth softball athletes (13.0 ± 2.0 years; 162.19 ± 9.75 cm; 60.80 ± 14.28 kg) completed a bilateral SLS and a health history questionnaire in which they indicated if they were currently experiencing any pain/discomfort. Due to the clinical significance of the current study, p < 0.10 was classified as nearing significance. A point-biserial correlation was run between the groups (pain and no pain) and all kinematic variables (maximal knee flexion, knee valgus/varus, vertical sacrum displacement, anterior pelvic tilt, and pelvic lateral tilt) at each event (45° descent, maximal knee flexion, and 45° ascent), across each phase (descent, ascent), and between legs. Increased vertical sacrum displacement was correlated with pain at 45° ascent and at maximal knee flexion in the right SLS. Knee valgus at maximal knee flexion, 45° ascent, and in the decent phase of the left SLS was significant. Anterior pelvic tilt in the decent phase of the left SLS and knee valgus and pelvic lateral tilt in the decent phase of the right SLS were found to be significantly correlated with pain. Poor SLS performance was correlated with reported pain.

Autoregulation in Resistance Training: A Comparison of Subjective Versus Objective Methods.

Shattock, K and Tee, JC. Autoregulation in resistance training: A comparison of subjective versus objective methods. J Strength Cond Res 36(3): 641-648, 2022-Autoregulation (AR) is a resistance training periodization approach that adjusts training prescription in response to individual rates of athlete adaptation. AR training prescription can make use of either subjective (rating of perceived exertion [RPE]) or objective (barbell velocity) intensity descriptors. The aim of this research was to compare the efficacy of these 2 approaches in improving sport-specific physical performance measures. Using a randomized crossover design, 20 amateur rugby union players completed two 6-week blocks of training with training intensity prescribed using either objective velocity-based (VB) (measured using a wearable accelerometer device) or objective RPE-based intensity prescriptions. Training volume was matched for both groups while training intensity was equivalent but prescribed using either VB or RPE measures. Performance measurements were countermovement jump (CMJ), 1 repetition maximum back squat and bench press, and 10-, 20-, and 40-m sprint. Testing was conducted before and immediately after each training block. The likelihood that observed changes in performance measures were meaningful was assessed using magnitude-based decisions. Both training programs induced practically meaningful improvements in CMJ (VB most likely +8.2, ±1.1%; RPE likely +3.8, ±0.9%), back squat (VB most likely +7.5, ±1.5%; RPE possibly +3.5, ±1.8%), and bench press (VB most likely +7.7, ±2.1%; RPE possibly +3.8, ±0.9%). Changes in sprint test performance were very likely trivial for both programs. Objective AR programming resulted in larger improvements in CMJ (likely 4.2, ±1.2%), squat (likely 3.7, ±1.5%) performance, and bench press (possibly 3.7, ±1.5%) performance. Autoregulation periodization improved strength and CMJ, but not sprint performance. Autoregulation effects are augmented through the use of objective intensity prescription.

The effects of alpha lipoic acid on muscle strength recovery after a single and a short-term chronic supplementation - a study in healthy well-trained individuals after intensive resistance and endurance training

BackgroundAlpha lipoic acid (ALA) has been demonstrated to have anti-inflammatory activity and was tested as a drug for the treatment of various diseases. ALA is also frequently used as a nutrition supplement, in healthy individuals or in competitive athletes. However, information from intervention studies investigating physiological effects of an ALA in athletes after exercise is limited. Therefore, the aim of this study was to investigate the effects of single and short-term chronic ALA supplementation on the muscle strength recovery and performance of athletes after intensive exercise.MethodsIn a double-blind, randomised, controlled trial in cross-over design, 17 male resistance and endurance-experienced athletes successfully participated. The subjects were divided into two groups (ALA and Placebo) and underwent a standardized single training session and a high intense training week. At certain time points (T0, T1a (+ 3 h), T1b (+ 24 h) and T2 (+7d)) blood samples were taken and markers for muscle damage, inflammation and oxidative stress were investigated. In addition, the maximum performance in the back squat was measured at all time points.ResultsIn the chronic training experiment, a moderate inhibition of muscle damage and inflammation could be observed in the ALA-group. Performance in the back squat was significantly reduced in the placebo-group, but not in the ALA-group. No anti-oxidative effects could be observed.ConclusionsOur data indicate possible effects of ALA supplementation, during intensive training periods result in a reduction of muscle damage, inflammation and an increase of recovery. Whether ALA supplementation in general may enhance performance and the exact training / supplementation scenarios needs to be investigated in future studies.

Relationship Between Lower Extremity Extensor Strength and Wall Squat Performance

Background: The wall squat exercise has been recommended for strengthening of the lower extremity muscles with maintaining lumbar lordosis. Although squat has been studied to be related to lower extremity extensor strength, the relationship between wall squat and lower extremity extensor strength unclear. Because squat and wall squat are biomechanically different, study on the relationship is needed.Objects: The purpose of this study was to determine the lower extremity extensor strength associated with wall squat performance.Methods: 74 healthy volunteers were recruited to participate in this study. The volunteers were measured hip and knee extensors strength and then performed wall squat exercise for maximum count.Results: We found significant relationships between wall squat performance and hip extensor strength normalized by body weight, knee extensor strength normalized by body weight and the composite value. In a regression analysis, hip extensor strength normalized by body weight explained 29% of the variation in wall squat performance in males and 35% in females.Conclusion: These results demonstrate that hip extensor strength normalized by body weight is critical to wall squat performance in both sexes.

Is deep squat movement strategy related to floor-to-waist height lifting strategy: implications for physical employment testing

Generalised predictive tests may be viable screening tools to evaluate job candidate workability if movement strategy used in assessment is consistent with movement strategy used in work. This study investigated if deep squat (DS) kinematics could predict floor-to-waist height lifting kinematics. Participants performed three DS repetitions, and 10 lifts of both a 10 kg and 20 kg box. Whole body kinematics were collected to calculate knee, hip and low back angles, and coordination as measured by relative phase angles. Movement features of lower extremity control, including knee and hip angles and coordination, were significantly correlated (r = 0.43–0.85) between the DS and lifting. However, low back movement features, measures linked to injury risk, were not significantly correlated between the DS and lifting. These findings do not support the DS as a suitable movement screen to predict lifting strategy, specifically when considering low back control. Practitioner summary: This study investigated whether lifting strategy could be inferred from deep squat performance. Knee and hip movement strategies were associated between the deep squat and lifting. However, inconsistencies in low back control between the deep squat and lifting limit the deep squat’s injury risk assessment potential.

Changes in Knee and Trunk Alignment in People With Hip Pain and Healthy Controls When Using a Decline Board During Single-Leg Squat.

Hip pain is associated with reduced hip muscle strength, range of movement (ROM), and decreased postural stability. Single-leg squat is a reliable and valid method to measure dynamic balance. To evaluate the influence of physical characteristics and use of a decline board on squat performance in a hip pain population. Cross-sectional study setting. Clinical Patients: In total, 33 individuals scheduled for arthroscopic hip surgery were matched with 33 healthy controls. Hip and ankle ROM, hip strength, and trunk endurance were assessed, along with knee and trunk kinematics during squat on flat and 25° decline surfaces. Between-group and surface differences in alignment, between-group strength and ROM, and associations between alignment and physical characteristics were assessed and determined using mixed model analysis of variance and Pearson R. The hip pain group had significantly less strength and ROM for all directions except abduction strength and ankle dorsiflexion (P > .02). No differences existed between the 2 groups for trunk (P < .70) or knee displacement (P < .46) during squat on either surface. When the 2 groups were combined (n = 66), decline squat significantly reduced knee medial displacement in both limbs by approximately 1 cm (P < .01). Decline squat reduced trunk lateral movement on 1 side only (P = .03). Reduced knee displacement during decline squat showed fair association with less hip-extension strength (r = -.29), hip-flexion strength (r = -.25), and less dorsiflexion (r = -.24). Strength and range were not associated with trunk displacement. Decline squat reduced medial knee and lateral trunk displacement regardless of hip pain. Reductions may be greater in those with lesser hip muscle strength and dorsiflexion. Use of a decline board during squat for improving knee and trunk alignment should be considered as a goal of exercise intervention.

Single-Leg Squat Performance and Its Relationship to Extensor Mechanism Strength After Anterior Cruciate Ligament Reconstruction

Background: Performance in strength and functional testing is important when considering return to sport after anterior cruciate ligament (ACL) reconstruction. Both knee extensor strength and the single-leg squat (SLS) have been used in this context. Purpose: To evaluate the relationship between knee extensor strength and SLS performance after primary ACL reconstruction. Study Design: Cohort study (Diagnosis); Level of evidence, 3. Methods: A prospective cohort of 100 patients was assessed 6 and 12 months after primary ACL reconstruction with a hamstring tendon autograft. Knee extensor peak torque was measured. Three sequential SLSs were performed, and the maximum flexion angle identified from frame-by-frame video analysis was used as the measure of squat performance. A limb symmetry index (LSI) was calculated and satisfactory performance defined as ≥90%. Results: Extensor mechanism strength deficits were seen in 75% of patients at 6 months and 57% at 12 months postoperatively. Mean extensor mechanism strength showed a large improvement between 6 and 12 months (123.6 vs 147.8 N·m, respectively; P < .001; Cohen d = 1.10), and while there was also a statistically significant improvement in the mean maximum flexion angle, the change was small (66.1° vs 68.1°, respectively; P = .011; Cohen d = 0.26). There was a weak positive correlation between knee extensor strength and the SLS maximum flexion angle at 6 months (r = 0.342; P < .001) and 12 months (r = 0.245; P = .014). An SLS LSI <90% was 80% specific and 35% sensitive for extensor mechanism weakness at 6 months and 79% specific and 18% sensitive at 12 months. Conclusion: Extensor mechanism strength deficits are common after ACL reconstruction but reduce between 6 and 12 months. The SLS maximum flexion angle has a weak linear relationship to knee extensor strength. SLS performance has high specificity but low sensitivity in identifying extensor mechanism strength deficits. The SLS maximum flexion angle is therefore a suboptimal surrogate test to identify extensor mechanism strength deficits as diagnosed by isokinetic dynamometric testing. However, unsatisfactory SLS performance indicates a very high chance of underlying extensor mechanism weakness.

Sport Specialization and Single-Legged-Squat Performance Among Youth Baseball and Softball Athletes.

Previous research has indicated that throwing sports expose athletes to overuse injuries and that specialization in sport is linked to injury. However, the effect of overexposure to a throwing sport on a dynamic movement task is unknown. To determine if sport specialization in youth throwing athletes affected performance on the single-legged squat (SLS). Descriptive laboratory study. University research laboratory. A total of 49 youth baseball and softball athletes (23 baseball, 26 softball; age = 12.96 ± 2.32 years, height = 165.01 ± 13.05 cm, mass = 61.42 ± 13.04 kg) were recruited. Participants were grouped into 3 categories based on specialization definitions: (1) 8 months or longer in season, (2) 8 months or longer in training, or (3) 8 months or longer in season and previously quit another sport. We measured SLS kinematics and used a set of 1-way multivariate analyses of variances to determine if trunk kinematics differed by group. Athletes who spent 8 months or more in sport-specific training exhibited significantly more trunk control, revealed by less trunk lateral flexion (Λ = 0.69, F6,38 = 2.89, P = .020) and less trunk flexion (Λ = 0.69, F6,38 = 2.88, P = .021) throughout an SLS. These results agree with the principle of specific adaptation to imposed demands. Surprisingly, athletes who spent 8 months or more playing a unilateral sport showed no differences in SLS performance. Clinicians should emphasize that neuromuscular adaptations of the lumbopelvic-hip complex for dynamic movement, such as an SLS, may be achieved through training instead of strict sport participation. Future researchers should consider how much of the training protocol is actually specialized for sport training.

Effects of Practical Blood Flow Restriction Training on Adolescent Lower-Body Strength.

Luebbers, PE, Witte, EV, and Oshel, JQ. Effects of practical blood flow restriction training on adolescent lower-body strength. J Strength Cond Res 33(10): 2674-2683, 2019-The purpose of this study was to examine the effects of a practical blood flow restriction (BFR) training program on lower-body strength of high school weightlifters. Twenty-five students were divided into 3 groups. For 6 weeks, each group completed the same resistance training program with the exception of the parallel back squat exercise (2 d·wk), which was different for each group. One group (HI) completed a traditional high-load (≥65% 1 repetition maximum [1RM]) back squat protocol with 3 sets of low repetitions (≤10). The LO group completed the squat exercise using a relatively light load (≤30% 1RM) for 1 set of 30 repetitions and 3 sets of 15 with 30 seconds of rest between sets. The LO + BFR group followed the same protocol as LO, but did so with blood flow restricted. One repetition maximum back squat tests were conducted before the start of the program and again on conclusion, the values of which were used as the dependent measure. A 3 × 2 (group × time) repeated-measures analysis of variance revealed a significant interaction (p = 0.043). Follow-up tests were conducted to explore the interaction. Paired-sample t-tests for each group indicated a significant increase in leg strength for the LO + BFR group (p = 0.005) but not for the HI (p = 0.142) or LO groups (p = 1.00). This suggests that a practical BFR training program may be effective in increasing 1RM squat performance of high school students.

Reliability of Squat Kinetics in Well-Trained Rugby Players: Implications for Monitoring Training.

Appleby, BB, Cormack, SJ, and Newton, RU. Reliability of squat kinetics in well-trained rugby players: implications for monitoring training. J Strength Cond Res 33(10): 2635-2640, 2019-The aim of this study was to determine the within-session reliability in kinetic variables of the squat in well-trained athletes during a typical resistance training protocol. Fifteen subjects completed 2 testing sessions. Session 1 was establishment of 1 repetition maximum (1RM) squat, and session 2 involved 2 sets of 2 maximal effort repetitions of the squat at 70, 80, and 90% of 1RM with 3D motion analysis and ground reaction force (GRF) measurement using 2 in-ground triaxial force plates. Reliability was calculated using typical error ± 90% confidence limits, expressed as the coefficient of variation and intraclass correlation coefficient. The smallest worthwhile change (SWC%), calculated as 0.2 × between-subject SD, was used to determine the smallest important change in performance. Peak GRF and average GRF were found to have acceptable measures of reliability with the combined left and right leg average GRF capable of detecting the SWC. Independent limb contributions were reliable (left and right, or dominant and nondominant). Reliable kinetics can be obtained in back squat performance typical of a resistance training session in well-trained athletes. This suggests that coaches integrating force plate technology within training sessions may effectively capture between 1 and 6 training sets among several athletes, facilitating analysis and intervention on larger data sets.

Impact of Cognitive Measures and Sleep on Acute Squat Strength Performance and Perceptual Responses Among Well-Trained Men and Women.

Haischer, MH, Cooke, DM, Carzoli, JP, Johnson, TK, Shipherd, AM, Zoeller, RF, Whitehurst, M, and Zourdos, MC. Impact of cognitive measures and sleep on acute squat strength performance and perceptual responses among well-trained men and women. J Strength Cond Res 35(2S): S16-S22, 2021-This study assessed the efficacy of currently used assessments for sleep, anxiety, and stress in predicting 1-repetition maximum (1RM) back squat performance. Fifty-three men (age, 23 ± 3 years; body mass, 86.67 ± 13.93 kg; training age, 6.0 ± 2.5 years; 1RM = 163.5 ± 39.5 kg) and 15 women (age, 21 ± 1.5 years; body mass, 63.34 ± 9.6 kg; training age, 4 ± 1.5 years; 1RM = 81.5 ± 12.5 kg) participated. Subjects completed the Daily Analysis of Life Demands for Athletes (DALDA), the revised Competitive State Anxiety Inventory-2 (CSAI-2R), and Oviedo Sleep Questionnaire (OSQ) to evaluate stress, anxiety, and sleep, respectively. Subjects then completed the perceived self-efficacy (PSE) scale, to predict what loads they were 100, 75, and 50% confident that they could lift for a 1RM; then completed 1RM testing with rating of perceived exertion (RPE) and average concentric velocity (ACV) obtained on each attempt. The performance-dependent variable was calculated by subtracting the PSE responses from the actual 1RM (1RM-PSE difference). Bootstrapping with 1,000 replicate samples was used with linear regression to increased robustness of the statistical analyses, and 95% confidence intervals (CIs) were calculated. Hours of sleep was an inverse predictor of ACV (p = 0.014; 95% CI = 0.046 to-0.011) and a positive predictor of RPE (p = 0.005; 95% CI = 0.068-0.342). Furthermore, the hypersomnia subscale of the OSQ was a negative predictor of 1RM-PSE difference at 50% confidence (p = 0.028; 95% CI = -3.507 to -0.528), and CSAI-2R total score was a negative predictor of RPE at 1RM (p = 0.043; 95% CI = -0.041 to -0.003); however, the DALDA did not exhibit any significant relationships. These data highlight the importance of monitoring anxiety and sleep when assessing readiness for maximal strength performance.

Hip Biomechanics During a Single-Leg Squat: 5 Key Differences Between People With Femoroacetabular Impingement Syndrome and Those Without Hip Pain

The hip joint biomechanics of people with femoroacetabular impingement (FAI) syndrome are different from those of healthy people during a double-leg squat. However, information on biomechanics during a single-leg squat is limited. To compare hip joint biomechanics between people with FAI syndrome and people without hip pain during double-leg and single-leg squats. Fourteen people with FAI syndrome (cam, n = 7; pincer, n = 1; mixed, n = 6) and 14 people without hip pain participated in this cross-sectional, case-control, laboratory-based study. Three-dimensional biomechanics data were collected while all participants performed a double-leg and a single-leg squat. Two-way mixed-model analyses of variance were used to assess group-by-task interactions for hip joint angles, thigh and pelvis segment angles, hip joint internal moments, and squat performance variables. Post hoc analyses for all variables with a significant group-by-task interaction were performed to identify between-group differences for each task. There were significant group-by-task interactions for peak hip joint (P = .014, η2 = 0.211) and thigh segment (P = .009, η2 = 0.233) adduction angles, and for peak hip joint abduction (P = .002, η2 = 0.308) and extension (P = .016, η2 = 0.203) internal moments. There were no significant group-by-task interactions for squat performance variables. Biomechanical differences at the hip between people with FAI syndrome and those without hip pain were exaggerated during a single-leg squat compared to a double-leg squat task. Diagnosis, level 4. J Orthop Sports Phys Ther 2019;49(12):908-916. Epub 23 Jul 2019. doi:10.2519/jospt.2019.8356.

Muscle Activation in Unilateral Barbell Exercises: Implications for Strength Training and Rehabilitation.

Mausehund, L, Skard, AE, and Krosshaug, T. Muscle activation in unilateral barbell exercises: Implications for strength training and rehabilitation. J Strength Cond Res 33(7S): S85-S94, 2019-The purpose of the present investigation was to assess lower-body muscle activity and hamstrings-to-quadriceps (HQ) activation ratios during performance of the split squat (SS), single-leg squat (SLS), and rear foot elevated split squat (RFESS), while using the same relative load and performing the exercises to muscular failure. Eleven healthy, moderately strength-trained subjects performed a 6-8 repetition maximum set of each exercise while electromyographic (EMG) activity of the vastus lateralis, biceps femoris, gluteus maximus, and gluteus medius was recorded. The results show that there were no significant differences in EMG peak activity of the gluteus maximus and vastus lateralis between any of the exercises. Gluteus medius activation was significantly (p ≤ 0.05) higher during the SLS (81.9% maximum voluntary isometric contraction [MVIC]), compared with the RFESS (54.9% MVIC) and SS (46.2% MVIC). The RFESS elicited higher (p ≤ 0.05) biceps femoris activity (76.1% MVIC) than the SS (62.3% MVIC), as well as higher (p ≤ 0.05) HQ activation ratios (0.83) than the SS (0.69) and SLS (0.63). During the SLS and the SS, HQ activation ratios increased significantly in the course of the repetition maximum set. In conclusion, although absolute loading differs between exercises, similar training stimuli of the gluteus maximus and quadriceps femoris can be expected for all exercises. The SLS is likely to induce the greatest improvements in gluteus medius strength, whereas the RFESS should be preferred if high hamstring coactivation is desired. To improve validity in EMG studies, strength training exercises should be performed close to failure while using the same relative loading.

A comparison of trunk and lower extremity muscle activity during the performance of squats and kneeling squats in persons with stroke: a preliminary study

A comparison of trunk and lower extremity muscle activity during the performance of squats and kneeling squats in persons with stroke: a preliminary study

Influence of Loaded Lunge Performance on Functional Movement Screen Deep Squat Performance in Physically Active Individuals

The Functional Movement Screen Deep Squat (DS) is used to assess the quality of fundamental movement patterns. Specifically, the DS assesses musculoskeletal stability and mobility at the ankle, knee, and hip. The DS score is added to a composite score to identify individuals at risk for musculoskeletal injury. PURPOSE: To examine the influence of ankle range of motion (ROM), as measured during a weight bearing lunge, on the individual scoring criteria and overall score for the DS. METHODS: Twenty-two college aged, physically active subjects (11 M, 11 F, 20.3 ± 1.0 yo) were recruited and completed testing. Bilateral peak weight bearing ankle dorsiflexion ROM was measured with a digital inclinometer during the loaded lunge test, with the lower bilateral scores being retained. Participants performed three trials of the DS with their feet flat and three trials with their heels elevated on a 2x6 block. Standard FMS scoring criteria were applied to assign a score of 3, 2, or 1. Successful completion of the DS requires; 1. torso to be parallel with the tibia or toward vertical, 2. femur to be parallel with the floor or below, 3. knees to track over the toes, & 4. dowel cannot move beyond the toes. A one-way ANOVA with a Bonferoni post hoc test and independent t-tests were used to determine significance (p ≤ 0.05) for the influence of ankle dorsiflexion ROM on DS scores and the presence of the four individual DS dysfunctions respectively. RESULTS: There was a significant difference in ankle dorsiflexion for DS scores [F(2, 19) = 5.20, p=0.016]. Post hoc testing revealed a significant difference in dorsiflexion ROM between a score of 3 (51.4° ± 9.7°) and a score of 1 (39.5° ± 5.6°). There was a significant difference (p=0.001) in ankle dorsiflexion for participants that met the torso/tibia criteria (51.0° ± 7.6°) compared to participants that did not meet the criteria (40.1° ± 5.0°), and for participants that met the dowel position criteria (50.5° ± 5.0°) compared to those that did not meet the criteria (41.5° ± 6.3°) (p=0.016). CONCLUSION: Participants with limited weight bearing ankle dorsiflexion ROM are more likely to score a 1 and exhibit a forward lean and bar position during the DS. This information will guide a clinician’s corrective exercise approach for individuals that exhibit these DS dysfunctions.

Influence of Heart Rate Variability Variables in Half Squat Performance in Female Athletes

The search of non-invasive and easy-to-monitor variables is essential to improve the athlete performance. The assessment of neuromuscular characteristics, such as velocity, with a lineal position transducer (LPT), allows training optimization and just like heart rate variability (HRV) guaranties an adequate athlete monitoring. The autonomic nervous system (ANS) and Sympathetic nervous system (SNS) exert an important influence on skeletal muscle functions. However, there are no studies that correlate the activity of SNS with current technologies such as LPT to calculate several neuromuscular performance variables. Otherwise, the results of HRV assessment could be related to a TLP strength test performance. PURPOSE: The aim of this study is to find correlations between HRV variables and TLC variables during a half squat movement in young female soccer players. METHODS: Thirteen professional female soccer players were tested (Age 20.7 years +/-2.62, Weight 60.9 kg +/- 4.4), we analyzed HRV during standing, we also evaluated the velocity of a half squat movement with a LPT, during a maximal strength test, statistical analyses were performed to determine associations. RESULTS: Associations were found between Stress index during standing position and Mean acceleration to Maximal velocity (m/s/s) (R2 0,3115 P 0,0381), Mean velocity (R2 0,3284 P 0,0322), Propulsive mean velocity (R2 0,3189 P 0,0354). CONCLUSIONS: Stress Index (SI) is a variable that reflects sympathetic activation and suggest autonomic reactivity to stress situations indicating an adequate response to confront the demands presented by the sport. Thus, an abnormal sympathetic predominance could result in chronic fatigue which would evince a SI higher elevation, giving the index greater value. According to our findings the SI during standing position correlated with velocity and acceleration variables during half squat, this suggests that adequate sympathetic reactivity could contribute to the improvement of neuromuscular variables. We hypothesized that SI could be a simple non-invasive way to measure sympathetic reactivity in sports, being part in assessment and monitoring of performance. We also suggest that interventions aimed to improve sympathetic reactivity could improve neuromuscular performance.