Muscle Activation Patterns of the Proximal Medial and Distal Biceps Femoris and Gluteus Maximus Among 6 Hip Extension and Knee Flexion Exercises in Trained Women.

The biceps femoris (BF) is a double-jointed muscle that performs both hip extension and knee flexion, making it a challenging muscle to train during common resistance training movements. An imbalance between the posterior and anterior chain increases the risk of lower-extremity injury. The purpose of this study was to compare BF proximal (BFprox), BF medial (BFmed), and BF distal (BFdist) peak and mean muscle activation among four hip hinging movements and two knee flexion movements. A secondary variable was gluteus maximus (GMax) muscle activation among the same six movements. Fifteen trained females completed three repetitions at 75% estimated 1-repetition max among the following exercises: Romanian-deadlift (RDL), step-up, hip-extension, kickbacks, Nordic hamstring curls (Nordics), and legcurls. Repetition voltage was normalized to percent maximal voluntary isometric contractions. Eight separate one-way repeated measures ANOVAs with Sidak post hoc analysis indicated the BFprox elicited greater voltage in the kickback, Nordic, and leg-curl exercise compared to the RDL, step-up and hip-extension (p < 0.05), BFmed voltage was higher in the hip-extension, kickback, Nordic, and leg-curl vs. the step-up and RDL (p < 0.05), BFdist voltage was greater during the kickback, Nordic, and leg-curl exercise vs. the RDL, step-up and hip-extension (p < 0.05), while the GMax elicited the lowest voltage during the leg-curl vs. the other five exercises (p < 0.05). All eight ANOVAs reached statistical significance (p < 0.01). The Nordic exercises consistently elicited the highest voltage among the six exercises. Coaches, trainers, and therapist can use these findings to target different aspects of the BF for training purposes and hamstring injury management.

Evaluation of short-term multi-component exercise programming on major variables that directly influence fall risk in older women: a pilot study.

Falls are linked to gait and balance inconsistencies influenced by a combination of variables including muscle strength and power. Multicomponent athlete training models that incorporate high-intensity challenging activities have been shown to significantly improve strength, power, and balance. This study evaluated the efficacy of a short-term multi-component dynamic training program on strength, power, and balance in older women. Seventeen women participated in 8-weeks of specialized exercise training. Significant changes were observed in all performance variables from baseline. Results suggest short-term, high intensity multi-component programming can be used safely and effectively to improve major variables that influence falls in older women.

The Influence of Normalization Technique on Between-Muscle Activation during a Back-Squat.

Currently, no gold standard electromyography (EMG) normalizing technique exists when conducting between-muscle comparisons of muscle activity during isotonic resistance training exercises. The aim of this study was to assess if between-muscle activation during the back-squat differed among electromyography (EMG) normalization techniques when normalizing to: (1) 1 repetition maximum (1RM), (2) maximal voluntary isometric contraction (MVIC), and (3) the first of a set of three repetitions (Rep1%) in trained female lifters. Thirteen participants completed a back-squat 1RM, MVIC of the rectus-femoris (RF) and gluteus-maximus (GM), and three repetitions of the back-squat at 80% 1RM. For the 1RM and MVIC normalization techniques, the average of the peak RMS signal of both muscles during the three submaximal reps were normalized to the peak 1RM and MVIC signals. The Rep1% averaged the peak RMS signals of both muscles during the 2nd and 3rd submaximal repetitions normalized to the peak signal during the 1st repetition. The RF-GM between-muscle EMG (ΔEMG) differed among normalization techniques (p < 0.001, ηp 2 = 0.48). Post-hoc pairwise comparisons indicated MVIC normalization elicited different ΔEMG with large effects compared to both 1RM (p = 0.037; d = 1.2) and Rep1% (p = 0.004; d = 1.9) techniques, but the 1RM and Rep1% did not produce different ΔEMG (p = 0.27; d = 0.8). Our findings suggest EMG normalization technique influences the magnitude and direction of between-muscle activation during common lifting exercises, and we recommend normalizing isotonic movements to dynamic normalization methods such as a 1RM or Rep1%.

Comparisons of Single Leg Squat Variations on Lower Limb Muscle Activation and Center of Pressure Alterations.

Following anterior cruciate ligament reconstruction, individuals experience inadequate functioning of the quadriceps and decreased muscular strength. Decreased function delays return to physical activity and increases potential for re-injury. While several squat variations exist, a new variation has emerged in rehabilitation. The purpose of this study was to compare muscle activation of the Vastus Lateralis (VL), Vastus Medialis (VM), Rectus Femoris (RF), Gluteus Maximus (GM), and anterior posterior center of pressure (AP displacement) alterations during a single leg squat variation (SLS variation) versus a traditional split squat using electromyography (EMG) in healthy active females. Seventeen females performed one set of both squat variations on a force plate while muscle activation was measured. Paired t-tests were used to compare dependent variable (DV) means between squat variations. Results indicated SLS variation yielded lower peak and mean quadriceps activation compared to traditional split squat, (p < 0.05). However, peak and mean GM muscle activity was greater in the SLS variation compared to the traditional split squat, (p < 0.01). Lastly, AP displacement was greater during the SLS variation, (p < 0.001). All three quadricep muscles had greater peak and mean EMG suggesting the traditional split squat be used for quadricep activation in rehabilitation/training settings, while the SLS variation should be prescribed for greater GM muscle activation. Understanding muscle activation patterns amongst squat variations can be practically applied by therapists, coaches and trainers to aid in reducing risks of arthrokinetic dysfunction via synergistic dominance, faster return to physical activity and normal functions of daily activity.

Self-Myofascial Release Does Not Improve Back Squat Range of Motion, Alter Muscle Activation, or Aid in Perceived Recovery 24-Hours Following Lower Body Resistance Training.

Self-myofascial release (SMR) is an alternative therapy believed to increase myofascial mobility by exciting muscles and increasing blood flow to the treated area. Previous literature suggest SMR produces conflicting results on performance, muscle activation, range of motion (ROM), and recovery. This study was designed to utilize SMR on a fatigued individual prior to exercise and measure its' effects on muscle activation, ROM, and perceived recovery compared to a dynamic warm-up session. The findings could help develop an efficient warm-up protocol for resistance-trained individuals. Electromyography (EMG) measured muscle activation of the rectus femoris (RF) and the gluteus maximus (GM), while a bluetooth goniometer assessed knee ROM during a submaximal back-squat. Eleven resistance trained participants (estimated squat 1RM 163% body weight) completed four total sessions of testing with sessions 1 and 3 solely used to induce muscle fatigue. In a counterbalanced design, participants during sessions 2 and 4 received either a dynamic standardized warm-up, or a SMR warm-up. Participants performed 10 repetitions of the back-squat at 70% estimated 1RM load. Peak and mean muscle activation of both muscles, knee ROM, and participants' perceived recovery was measured during the submaximal repetitions during sessions 2 and 4. Results indicated no significant differences between the dynamic warm-up and SMR warm-up among muscle activation, knee ROM, and participants perceived recovery (p > 0.05). In resistance trained squatters, coaches/trainers can prescribe SMR or a dynamic warm-up/stretching routine for results indicated no differences in perceived recovery, muscle activation, or squat depth.

Muscle Activation Patterns of Lower-Body Musculature Among 3 Traditional Lower-Body Exercises in Trained Women.

Korak, JA, Paquette, MR, Fuller, DK, Caputo, JL, and Coons, JM. Muscle activation patterns of lower-body musculature among 3 traditional lower-body exercises in trained women. J Strength Cond Res 32(10): 2770-2775, 2018-The deadlift and back and front squats are common multijoint, lower-body resistance exercises that target similar musculature. To our knowledge, muscle activity measured using surface electromyography has never been analyzed among these 3 exercises. Furthermore, most literature examining this topic has included male participants creating a void in the literature for the female population. Knowledge of lower-body muscle activation among these 3 exercises can aid coaches, trainers, and therapists for training and rehabilitative purposes. Trained women (n = 13) completed 2 days of testing including a 1-repetition maximum (1RM) estimation, an actual 1RM, and 3 repetitions at 75% 1RM load for the deadlift and back and front squats. Muscle activity of the 3 repetitions of each muscle was averaged and normalized as a percentage to the 1RM lifts for the deadlift and front and back squats. Five separate repeated-measure analysis of variances were performed indicating muscle activity of the gluteus maximus (GM) differed among the 3 exercises (p = 0.01, (Equation is included in full-text article.)= 0.39). Specifically, post hoc analysis indicated greater muscle activity during the front squat (M = 94%, SD = 15%) compared with the deadlift (M = 72%, SD = 16%; p ≤ 0.05) in the GM. No significant differences were observed among the lifts in the vastus medialis, vastus lateralis, biceps femoris, and rectus femoris. Strength and conditioning specialist and trainers can use these findings by prescribing the front squat to recruit greater motor units of the GM.

Effect of rest-pause vs. traditional bench press training on muscle strength, electromyography, and lifting volume in randomized trial protocols.

PURPOSE: Rest-pause (4-s unloaded rest between repetitions) training effects on one repetition maximum (1 RM), lifting volume, and neural activation via electromyography (EMG) are currently vague in the literature and can benefit strength and conditioning professionals for resistance training programme design. Therefore, this study compared 1 RM, neural activation via (EMG), and volume differences between rest-pause vs. traditional resistance training. METHODS: Trained males (N = 20) were randomly assigned to either a rest-pause or a traditional training group. Pre- and post-1 RM testing was recorded. Training sessions were completed twice a week for 4 weeks and consisted of four sets of bench press to volitional fatigue at 80% of pre-test 1 RM with a 2-min rest between sets. Total volume completed was recorded on each training day. Neural activation of the pectoralis major was measured on the first and last training days. RESULTS: A two-way repeated-measures ANOVA indicated both groups significantly increased their 1 RMs following the 4-week training protocol (p < .05). However, no significant differences were found in 1 RM and neural activation between the two groups (p > .05). An independent samples t test indicated that total volume lifted was significantly higher for the rest-pause group (56,778 vs. 38,315 lbs; p < .05) throughout the protocol and independently during weeks 2, 3, and 4. CONCLUSIONS: While strength and neural activation changes did not differ between groups, both increased 1 RMs and the rest-pause group achieved greater increases in volume than the traditional group. If volume is the focus of training, the rest-pause method should be utilized.