A comparison of two gluteus maximus EMG maximum voluntary isometric contraction positions

Background. The purpose of this study was to compare the peak electromyography (EMG) of the most commonly-used position in the literature, the prone bent-leg (90°) hip extension against manual resistance applied to the distal thigh (PRONE), to a novel position, the standing glute squeeze (SQUEEZE). Methods. Surface EMG electrodes were placed on the upper and lower gluteus maximus of thirteen recreationally active females (age = 28.9 years; height = 164 cm; body mass = 58.2 kg), before three maximum voluntary isometric contraction (MVIC) trials for each position were obtained in a randomized, counterbalanced fashion. Results. No statistically significant (p \u3c 0.05) differences were observed between PRONE (upper: 91.94%; lower: 94.52%) and SQUEEZE (upper: 92.04%; lower: 85.12%) for both the upper and lower gluteus maximus. Neither the PRONE nor SQUEEZE was more effective between all subjects. Conclusions. In agreement with other studies, no single testing position is ideal for every participant. Therefore, it is recommended that investigators employ multiple MVIC positions, when possible, to ensure accuracy. Future research should investigate a variety of gluteus maximus MVIC positions in heterogeneous samples

A Comparison of Increases in Volume Load Over 8 Weeks of Low-Versus High-Load Resistance Training

Background: It has been hypothesized that the ability to increase volume load (VL) via a progressive increase in the magnitude of load for a given exercise within a given repetition range could enhance the adaptive response to resistance training. Objectives: The purpose of this study was to compare changes in volume load (VL) over eight weeks of resistance training (RT) in high-versus low-load protocols. Materials and Methods: Eighteen well-trained men were matched according to baseline strength were randomly assigned to either a low-load RT(LOW,n= 9) where 25 - 35 repetitions were performed per exercise, or a high-load RT (HIGH,n= 9) where 8 - 12 repetitions were performed per exercise. Both groups performed three sets of seven exercises for all major muscles three times per week on nonconsecutive days. Results: After adjusting for the pre-test scores, there was a significant difference between the two intervention groups on post intervention total VL with a very large effect size (F (1, 15) = 16.598, P = .001, p2 = .525). There was a significant relationship between pre-intervention and post-intervention total VL (F (1, 15) = 32.048, P \u3c .0001, p2 = .681) in which the pre-test scores explained 68% of the variance in the post-test scores. Conclusions: This study indicates that low-load RT results in greater accumulations in VL compared to high-load RT over the course of 8 weeks of training

Hip thrust and back squat training elicit similar gluteus muscle hypertrophy and transfer similarly to the deadlift

We examined how set-volume equated resistance training using either the back squat (SQ) or hip thrust (HT) affected hypertrophy and various strength outcomes. Untrained college-aged participants were randomized into HT (n = 18) or SQ (n = 16) groups. Surface electromyograms (sEMG) from the right gluteus maximus and medius muscles were obtained during the first training session. Participants completed 9 weeks of supervised training (15–17 sessions), before and after which gluteus and leg muscle cross-sectional area (mCSA) was assessed via magnetic resonance imaging. Strength was also assessed prior to and after the training intervention via three-repetition maximum (3RM) testing and an isometric wall push test. Gluteus mCSA increases were similar across both groups. Specifically, estimates [(−) favors HT (+) favors SQ] modestly favored the HT versus SQ for lower [effect ±SE, −1.6 ± 2.1 cm2; CI95% (−6.1, 2.0)], mid [−0.5 ± 1.7 cm2; CI95% (−4.0, 2.6)], and upper [−0.5 ± 2.6 cm2; CI95% (−5.8, 4.1)] gluteal mCSAs but with appreciable variance. Gluteus medius + minimus [−1.8 ± 1.5 cm2; CI95% (−4.6, 1.4)] and hamstrings [0.1 ± 0.6 cm2; CI95% (−0.9, 1.4)] mCSA demonstrated little to no growth with small differences between groups. mCSA changes were greater in SQ for the quadriceps [3.6 ± 1.5 cm2; CI95% (0.7, 6.4)] and adductors [2.5 ± 0.7 cm2; CI95% (1.2, 3.9)]. Squat 3RM increases favored SQ [14 ± 2 kg; CI95% (9, 18),] and hip thrust 3RM favored HT [−26 ± 5 kg; CI95% (−34, −16)]. 3RM deadlift [0 ± 2 kg; CI95% (−4, 3)] and wall push strength [−7 ± 12N; CI95% (−32, 17)] similarly improved. All measured gluteal sites showed greater mean sEMG amplitudes during the first bout hip thrust versus squat set, but this did not consistently predict gluteal hypertrophy outcomes. Squat and hip thrust training elicited similar gluteal hypertrophy, greater thigh hypertrophy in SQ, strength increases that favored exercise allocation, and similar deadlift and wall push strength increases

The James Webb Space Telescope Mission

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure

Kinematics, Kinetics, and Electromyography of Vertical and Horizontal Hip Extension Exercises and Their Transference to Acceleration and Power

The squat is a very popular exercise in resistance training, utilized by populations ranging from clinical to elite athletes. A myriad of literature has shown that squats are effective for improving strength, performance, and hypertrophy. Due to the inherent nature of the squat, it is loaded vertically, or axially. The hip thrust, however, is a new, horizontally-, or anteroposteriorly-loaded exercise utilized to work the hip extensors, especially at end-range hip extension. The nature of the hip thrust makes it especially useful for achieving maximal gluteus maximus activation, as maximal activation is elicited at end-range hip extension, and may therefore be useful for achieving remarkable increases in gluteus maximus strength and hypertrophy. Furthermore, the horizontal nature of the hip thrust may mean that it carries over well to horizontally-oriented activities, such as pushing or sprinting. In order to test these hypotheses, a number of studies were carried out. Interestingly, it was found that there is no statistically significant difference in electromyographic amplitude between squat parallel, full, and front squat variations, and that there is no difference (p > 0.05) in electromyographic amplitude between barbell, American, and band hip thrust variations. The barbell hip thrust elicits much greater (mean upper gluteus maximus ES = 1.55; mean lower gluteus maximus ES = 1.65; mean biceps femoris ES = 1.58) hip extensor electromyographic activity than does the parallel squat, and is also beneficial for concentric force outputs (ES = 0.48). The squat, however, displayed a number of kinetic and temporospatial advantages over the hip thrust, including greater bar displacement (ES = 5.59) and potentially total work, impulse, and repetition time (ES = 0.51–1.00). A randomized-controlled trial was then performed to investigate how these differences transfer to training in adolescent male athletes. It appears that the hip thrust effectively improves a number of performance measures, including 20 m sprint times (ES = 1.14) and isometric mid-thigh pull strength (ES = 1.11). The front squat effectively increased vertical jump (ES = 1.11). Between-group comparisons revealed a number of benefits to the hip thrust over the front squat, including 10 and 20 m sprint times (ES = 0.32 and 0.39, respectively) and isometric mid-thigh pull strength (ES = 1.35 and 0.76 for absolute and normalized, respectively), and possible trivial benefits for horizontal jump performance (ES = 0.15). The front squat displayed a possibly beneficial effect for vertical jump performance (ES = –0.47). Finally, a single-subject six-week training study was conducted on monozygotic twins, wherein gluteus maximus hypertrophy and strength outcomes were measured. The squat and hip thrust exercises both increased upper and lower gluteus maximus thickness (upper: 20.7% (squat) vs. 23.5% (hip thrust); lower: 20.3% (squat) vs. 23.1% (hip thrust)), with the hip thrust being more effective at increasing upper gluteus maximus thickness compared to the squat (upper: 2.73%; lower: 2.89%). The hip thrust increased maximum horizontal force, 1 RM hip thrust, and 1 RM squat strength (31.8–65.0%), whereas the squat only increased 1 RM squat and 1 RM hip thrust (19.9–63.2%). This thesis provides evidence that the direction of the force vector in relation to the exerciser’s body plays a role in determining the transfer to performance

Bodyweight strength training anatomy/ Contreras

x, 212 hal.: ill.; 25 cm

Bodyweight strength training anatomy/ Contreras

x, 212 hal.: ill.; 25 cm

An examination of the gluteal muscle activity associated with dynamic hip abduction and hip external rotation exercise: a systematic review

Background: A wide variety of hip abduction and hip external rotation exercises are used for training, both in athletic performance and in rehabilitation programming. Though several different exercises exist, a comprehensive understanding of which exercises best target the gluteus maximus (Gmax) and gluteus medius (Gmed) and the magnitude of muscular activation associated with each exercise is yet to be established. Purpose: The purpose of this systematic review was to quantify the electromyographic (EMG) activity of exercises that utilize the Gmax and Gmed muscles during hip abduction and hip external rotation. Methods: Pubmed, Sports Discuss, Web of Science and Science Direct were searched using the Boolean phrases (gluteus medius OR gluteus maximus) AND (activity OR activation) AND (electromyography OR EMG) AND (hip abduction OR hip external rotation). A systematic approach was used to evaluate 575 articles. Articles that examined injury-free participants of any age, gender or activity level were included. No restrictions were imposed on publication date or publication status. Articles were excluded when not available in English, where studies did not normalize EMG activity to maximum voluntary isometric contraction (MVIC), where no hip abduction or external rotation motion occurred or where the motion was performed with high acceleration. Results: Twenty-three studies met the inclusion criteria and were retained for analysis. The highest Gmax activity was elicited during the lateral step up, cross over step up and rotational single leg squat (ranging from 79 to 113 % MVIC). Gmed activity was highest during the side bridge with hip abduction, standing hip abduction with elastic resistance at the ankle and side lying hip abduction (ranging from 81 to 103 % MVIC). Limitations: The methodological approaches varied between studies, notably in the different positions used for obtaining MVIC, which could have dramatically impacted normalized levels of gluteal activation, while variation also occurred in exercise technique and/or equipment. Conclusions: The findings from this review provide an indication for the amount of muscle activity generated by basic strengthening and rehabilitation exercises, which may assist practitioners in making decisions for Gmax and Gmed strengthening and injury rehabilitation program

Biomechanical implications of skeletal muscle hypertrophy and atrophy: a musculoskeletal model

Muscle hypertrophy and atrophy occur frequently as a result of mechanical loading or unloading, with implications for clinical, general, and athletic populations. The effects of muscle hypertrophy and atrophy on force production and joint moments have been previously described. However, there is a paucity of research showing how hypertrophy and atrophy may affect moment arm (MA) lengths. The purpose of this model was to describe the mathematical relationship between the anatomical cross-sectional area (ACSA) of a muscle and its MA length. In the model, the ACSAs of the biceps brachii and brachialis were altered to hypertrophy up to twice their original size and to atrophy to one-half of their original size. The change in MA length was found to be proportional to the arcsine of the square root of the change in ACSA. This change in MA length may be a small but important contributor to strength, especially in sports that require large joint moments at slow joint angular velocities, such as powerlifting. The paradoxical implications of the increase in MA are discussed, as physiological factors influencing muscle contraction velocity appear to favor a smaller MA length for high velocity movements but a larger muscle MA length for low velocity, high force movements

Roman Chair Back Extension Is/Is Not A Safe And Effective Exercise?

The roman chair back extension exercise is performed with the intent of improving hip and spinal extensor muscle performance. Despite evidence supporting the aforementioned benefits, performance of this exercise may increase the risk for low back pain among certain population subgroups. Although a clear verdict on the risk-to-benefit ratio remains elusive, a discussion of available scientific evidence (or lack thereof) should provide strength and conditioning professionals with information necessary for decision making. We want to hear from you. Visit nsca-scj.com to weigh in on the point/counterpoint quick poll