The Quantification of Muscle Activation During the Loaded Carry Movement Pattern.

The 'loaded carry' is a popular resistance training activity that activates core musculature across multiple movement planes while the body is in locomotion. 'Hold' exercises are similar to carry exercises but lack the locomotive aspect. Both carry and hold exercises can be completed bilaterally (farmer's carry (FC) and hold (FH)) or unilaterally (suitcase carry (SC) and hold (SH)). A deeper understanding of muscle activation between the FC and SC and intensity-matched FH and SH might improve their application. Healthy, college-aged individuals were recruited and surface electromyography of the rectus abdominis (RA), external oblique (EO), longissimus (LT), and multifidus (MF) was measured bilaterally using standard procedures. Participants completed time- and intensity-matched randomized sets of the plank, FC, SC, FH, and SH separated by 5-minute rests. A one-way ANOVA was utilized to compare exercises. The FC/FH load averaged 50.7±1.9 kg, where it was used across equally weighted dumbbells. The FC elicited higher activation bilaterally in the LT, MF, RA, and EO, compared to the FH. The SC/SH single-dumbbell load averaged 25.3±0.95 kg. There was greater activation bilaterally in the LT and MF during the SC compared to the SH. However, on the ipsilateral side of the SC, the RA and EO displayed greater activation compared to the SH, but this was not different on the contralateral side. The FC and SC were characterized by increased core muscle activation bilaterally, with the SC exhibiting unique additions to ipsilateral muscle activation.

A Comparison of Muscle Recruitment Across Three Straight-Legged, Hinge-Pattern Resistance Training Exercises.

Hinge exercises are critical to building a balanced resistance training program in concert with 'knee-dominant' (e.g., squat, lunge) exercises. Biomechanical differences between various straight-legged hinge (SLH) exercises may alter muscle activation. For example, a Romanian deadlift (RDL) is a closed-chain SLH, while a reverse hyperextension (RH) is open-chain. Likewise, the RDL offers resistance via gravity while the cable pull-through (CP) offers redirected-resistance through a pulley. A deeper understanding of the potential impact of these biomechanical differences between these exercises may improve their application to specific goals. Participants completed repetition-maximum (RM) testing on the RDL, RH, and CP. On a follow-up visit, surface electromyography of the longissimus, multifidus, gluteus maximus, semitendinosus, and biceps femoris, muscles that contribute to lumbar/hip extension, was recorded. After a warm-up, participants completed maximal voluntary isometric contractions (MVICs) in each muscle. They then completed five repetitions of the RDL, RH, and CP at 50% of estimated one RM. Testing order was randomized. A one-way, repeated-measures ANOVA test was used in each muscle to compare activation (%MVIC) across the three exercises. Shifting from a gravity-(RDL) to a redirected-resistance (CP) SLH significantly decreased activation in the longissimus (-11.0%), multifidus (-14.1%), biceps femoris (-13.1%), and semitendinosus (-6.8%). Alternately, changing from a closed-(RDL) to an open-chain (RH) SLH significantly increased activation in the gluteus maximus (+19.5%), biceps femoris (+27.9%), and semitendinosus (+18.2). Alterations in the execution of a SLH can change muscle activation in lumbar/hip extensors.

Stability of Resistance Training Implement alters EMG Activity during the Overhead Press.

Kettlebells often replace dumbbells during common resistance training exercises such as the overhead press. When performing an overhead press, the center of mass of a dumbbell is in line with the glenohumeral joint. In comparison, the center of mass of the kettlebell is posterior to the glenohumeral joint. Posterior displacement of the kettlebell center of mass may result in less stability during the pressing motion. The purpose of this study was to examine muscle activity during an overhead press with resistance training implements of differing stability. Surface electromyography (EMG) for the anterior deltoid and pectoralis major was analyzed for 21 subjects. Technique and pace of the overhead press were standardized and monitored. Filtered EMG data were collected, normalized, and average peak amplitude as a percentage of MVIC was calculated for each repetition. A repeated-measures analysis of variance was used to compare EMG values for the anterior deltoid and pectoralis major across implements. A statistically significant increase in normalized EMG activity (p < .05) was identified in the anterior deltoid when using the dumbbell (63.3±13.3%) compared to the kettlebell (57.9±15.0%). In this study, EMG activity was augmented in the anterior deltoid when using the more stable implement, the dumbbell.

Unanticipated ankle inversions are significantly different from anticipated ankle inversions during drop landings: overcoming anticipation bias.

Few ankle inversion studies have taken anticipation bias into account or collected data with an experimental design that mimics actual injury mechanisms. Twenty-three participants performed randomized single-leg vertical drop landings from 20 cm. Subjects were blinded to the landing surface (a flat force plate or 30° inversion wedge on the force plate). After each trial, participants reported whether they anticipated the landing surface. Participant responses were validated with EMG data. The protocol was repeated until four anticipated and four unanticipated landings onto the inversion wedge were recorded. Results revealed a significant main effect for landing condition. Normalized vertical ground reaction force (% body weights), maximum ankle inversion (degrees), inversion velocity (degrees/second), and time from contact to peak muscle activation (seconds) were significantly greater in unanticipated landings, and the time from peak muscle activation to maximum VGRF (second) was shorter. Unanticipated landings presented different muscle activation patterns than landings onto anticipated surfaces, which calls into question the usefulness of clinical studies that have not controlled for anticipation bias.