Effects of hand and knee positions on muscular activity during trunk extension exercise with the Roman chair

Do maximal isometric trunk tasks produce maximum activity in latissimus dorsi?

INTRODUCTION

Electromyography (EMG) studies investigating latissimus dorsi activity during trunk tasks have reported high activation levels and described latissimus dorsi as an important contributor to trunk movement and stability. However, the normalisation of EMG data in these studies is inconsistent with some normalising to shoulder tasks and a majority normalising to trunk tasks. Therefore, this study aimed to compare commonly used shoulder and trunk normalisation tasks to determine if trunk tasks produce maximum activity in latissimus dorsi.

METHODS

Ten asymptomatic participants completed maximal isometric trunk (extension, ipsilateral rotation and ipsilateral lateral flexion) and shoulder (extension and internal rotation) tasks while recording EMG signals from right latissimus dorsi using surface and indwelling electrodes. The signals were high-pass filtered, rectified then low-pass filtered to obtain an EMG linear envelope to represent muscle activity levels. The maximum activity levels across tasks were compared for each electrode type.

RESULTS

Shoulder extension elicited significantly higher (>1.5 times) latissimus dorsi activity levels when recorded using both surface and indwelling electrodes compared to other shoulder and trunk tasks.

CONCLUSION

Maximal isometric trunk tasks do not produce maximal latissimus dorsi activity and therefore when used for normalisation purposes potentially overestimate the contribution of latissimus dorsi to trunk tasks.

The Application of Surface Electromyography Technology in Evaluating Paraspinal Muscle Function

Surface electromyography (sEMG) has emerged as a valuable tool for assessing muscle activity in various clinical and research settings. This review focuses on the application of sEMG specifically in the context of paraspinal muscles. The paraspinal muscles play a critical role in providing stability and facilitating movement of the spine. Dysfunctions or alterations in paraspinal muscle activity can lead to various musculoskeletal disorders and spinal pathologies. Therefore, understanding and quantifying paraspinal muscle activity is crucial for accurate diagnosis, treatment planning, and monitoring therapeutic interventions. This review discusses the clinical applications of sEMG in paraspinal muscles, including the assessment of low back pain, spinal disorders, and rehabilitation interventions. It explores how sEMG can aid in diagnosing the potential causes of low back pain and monitoring the effectiveness of physical therapy, spinal manipulative therapy, and exercise protocols. It also discusses emerging technologies and advancements in sEMG techniques that aim to enhance the accuracy and reliability of paraspinal muscle assessment. In summary, the application of sEMG in paraspinal muscles provides valuable insights into muscle function, dysfunction, and therapeutic interventions. By examining the literature on sEMG in paraspinal muscles, this review offers a comprehensive understanding of the current state of research, identifies knowledge gaps, and suggests future directions for optimizing the use of sEMG in assessing paraspinal muscle activity.

Biceps Femoris Activation during Hamstring Strength Exercises: A Systematic Review

BACKGROUND

The aim of the study was to systematically evaluate the biceps femoris long head activation across cross-sectional hamstring strength exercise studies.

METHODS

A systematic review design was followed. The search strategy conducted in PubMed, Cochrane Library, and Web of Sciences databases found a total of 3643 studies. Once inclusion and exclusion criteria were applied, 29 studies were finally included in this systematic review. A total of 507 participants and 114 different exercises were analyzed. Exercises were evaluated individually and grouped into several categories: Nordics, isokinetic exercises, lunges, squats, deadlifts, good mornings, hip thrusts, bridges, leg curls, swings, hip and back extensions, and others.

RESULTS

Results showed the isokinetic and Nordic exercises as the categories with highest biceps femoris activation (>60% of Maximal Voluntary Isometric Contraction). Nordic hamstring exercise ankle dorsiflexion was the exercise that achieved the highest biceps femoris long head activation (128.1% of its Maximal Voluntary Isometric Contraction).

CONCLUSIONS

The results from this systematic review suggest that isokinetic and Nordic exercises seem to be the best option to activate biceps femoris long head. Future studies evaluating the implementation of these exercises in prevention programs are needed.

Effect of slope angle on muscle activity during variations of the Nordic exercise

This study investigated the muscular activity of the lower muscles during variation of Nordic exercises following changes of the Nordic angles and the base slope angles. Twenty-one healthy participants were participated in this study. Participants performed six variations of Nordic exercises including two Nordic angles positions and three base slope angles. Each Nordic exercise defined as Nordic angle 10°, 15° and base slope angle 0°, 10°, 15°. During the Nordic exercises, erector spine, gluteus maximus, biceps femoris, gastrocnemius activities and subjective difficulties (Borg RPE score) were measured. The activities of all muscles and subjective difficulties were significantly greater with the 15° of Nordic exercise compared to the 10° of Nordic exercise, regardless of base slope angles. There were significant differences in gluteus maximus, biceps femoris, gastrocnemius, and the Borg RPE score between three base slope conditions (P<0.05). The Borg RPE score and activities of the gluteus maximus were increased with the increases of base slop angles from 0° to 15°. Conversely, the activities of the gastrocnemius and biceps femoris were decreased with the increases of base slop angles from 0° to 15°. Present study indicates that application of the greater Nordic angle during the Nordic exercise is advantageous for activating lower extremity muscles. Using the base slopes during the Nordic exercise could be used for selective activation of the lower muscles. High base slope angles inducing greater knee flexion could maximize the exercise effects for activating gluteal muscles rather than lower leg muscles such as biceps femoris and gastrocnemius.

Effect of the body mass index and sexual difference on the muscle activity during trunk exercise: a preliminary study

There was lack of study which evaluated the effects of characteristics of subjects such as the body mass index (BMI) or waist circumference (WC), as well as sexual differences on trunk muscle activities. The purpose of the present study was to compare the abdominal muscle activities among the groups dividing criterion as the BMI, WC, and the gender. As a criterion of BMI and WC, subjects were arranged to three groups. Female subjects who were less than 25 kg/m² BMI, and less than 90 WC were arranged as female with underweight group (FU), male subjects who were greater than 25 kg/m² BMI and greater than 85 WC were arranged as male with overweight group (MO), male subjects who were less than 25 kg/m² BMI and less than 85 WC were arranged in male with underweight group (MU). Surface electromyography responses of the rectus abdominis, internal oblique, external oblique muscles and lumbar level of erector spinae were obtained during the plank and maximal voluntary isometric contraction (MVIC). The MO group showed significantly higher %MVIC value of the internal oblique and lumbar level of erector spinae, compared to the MU group (P<0.05). The %MVIC of the rectus abdominis was significantly greater with the FU group (P<0.05). There were significant differences in the root mean squared (RMS) values from MVIC among the three groups (P<0.05). Regardless of muscles differences, the MO group showed significantly lower RMS activity values than the FU and the MU groups (P<0.05). Present study indicates some considerations of interpreting surface electromyography (sEMG) signal from region overlapping large fat tissue especially for trunk muscles. Individual characteristics such as gender, BMI, and WC could affect the sEMG signals. The female and male with overweight represent relatively high %MVICs during exercise, but it might be due to relatively low RMS values from procedure of MVICs.