Peak Muscle Activity Research Articles

Effect of a Simultaneous Mental Arithmetic Task to a MMH Lifting Task on Muscle Activity in the Trunk and Shoulders

Introduction: This study investigated the effects of concurrent mental demands on material handling tasks. Methods: Eleven subjects performed a material handling task with and without cognitive loads while lifting a 5 kg box to three different destination heights. The cognitive load was created by having participants perform a concurrent math task while lifting the box. The study measured the muscle activity in trunk and shoulder muscles. Results: The study found that, in select muscles, the cognitive load conditions led to longer lift times and increased cumulative muscle activity, but lower peak muscle activity. Conclusion: These findings suggest that lifting tasks with a concurrent cognitive load could lead to greater cumulative muscle activity, increasing the risk of muscular fatigue during manual material handling tasks.

Muscle function during cross-country skiing at different speed and incline conditions.

The human musculoskeletal system is well adapted to use energy-efficient muscle-tendon mechanics during walking and running, but muscle behaviour during on-snow locomotion is unknown. Here, we examined muscle and muscle-tendon unit behaviour during diagonal-style cross-country roller skiing at three speed and incline conditions to examine whether skiers can exploit energy-saving mechanisms of the muscle-tendon unit. We assessed lower leg muscle and muscle-tendon unit mechanics and muscle activity in 13 high-level skiers during treadmill roller skiing using synchronised ultrasound, motion capture, electromyography and ski-binding force measurements. Participants skied using diagonal style at 2.5 and 3.5 m s-1 up 5deg, and at 2.5 m s-1 up 10deg. We found an uncoupling of muscle and joint behaviour during most parts of the propulsive kick phase in all conditions (P<0.01). Gastrocnemius muscle fascicles actively shortened ∼0.9 cm during the kick phase, while the muscle-tendon unit went through a stretch-shortening cycle. Peak muscle-tendon unit shortening velocity was 5 times faster than fascicle velocity (37.5 versus 7.4 cm s-1, P<0.01). Steeper incline skiing was achieved by greater muscle activity (24%, P=0.04) and slower fascicle shortening velocity (3.4 versus 4.5 cm s-1, P<0.01). Faster speed was achieved by greater peak muscle activity (23%, P<0.01) and no change in fascicle shortening velocity. Our data show that, during diagonal-style cross-county skiing, muscle behaviour is uncoupled from the joint movement, which enables beneficial contractile conditions and energy utilisation with different slopes and speeds. Active preloading at the end of the glide phase may facilitate these mechanisms.

Muscle coordination patterns in regulation of medial gastrocnemius activation during walking

The ankle plantar flexion in the late stance phase is referred to as the ankle push-off. When the ankle push-off force is enhanced, compensatory adjustments occur in the adjacent phases. The muscle control that achieves these compensatory movements remains unknown, although they are expected to be coordinately regulated across multiple muscles and phases. Muscle synergy is used as a quantification technique for muscle coordination, and this analysis enables the comparison of synchronized activity between multiple muscles. Therefore, this study aimed to elucidate the tuning of muscle synergies in muscle activation adjustment of push-off. It is hypothesized that muscle activation adjustment of push-off is performed in the muscle synergy related to ankle push-off and in the muscle synergy that activates during the adjacent push-off phase. Eleven healthy men participated, and participants manipulated the activity of the medial gastrocnemius during walking through visual feedback. Two conditions were compared as experimental conditions: increasing the muscle activity to 1.6 times that during normal walking (High) and matching it with that during normal walking (Normal). Twelve muscle activities in the trunk and lower limb and kinematic data were recorded. Muscle synergies were extracted by the non-negative matrix factorization. No significant difference was observed in the number of synergies (High: 3.5 ± 0.8, Normal: 3.7 ± 0.9, p = 0.21) and muscle synergy activation timing and duration between the High and Normal conditions (p > 0.27). However, significant differences were observed in the peak muscle activity during the late stance phase of the rectus femoris (RF), biceps femoris (BF) between conditions (RF at High: 0.32 ± 0.21, RF at Normal: 0.45 ± 0.17, p = 0.02; BF at High: 0.16 ± 0.01, BF at Normal: 0.08 ± 0.06 p = 0.02). Although the quantification of force exertion has not been conducted, the modulation of RF and BF activation could have occurred due to the attempts to help knee flexion. Muscle synergies during normal walking are therefore maintained, and slight adjustments in the amplitude of muscle activity occurred for each muscle.

P28: Analysis of Surface Electromyography (sEMG) Signals for Motion Signatures in Strength Training Exercises via Stretchable Wearable Electronic Sensors

Background: The characterization of commonly used strength training exercises has a range of implications for analysis of techniques displaying proper form and injury prevention in both sports and clinical rehabilitation settings. This study examines the ability of wearable sensors to effectively determine the degree of activation of different muscle groups using surface electromyography (sEMG) signals. The interpretation of these signals across muscle groups within an exercise allow for the characterization of their motion signatures. Wearable sensors with embedded electrodes (BioStamps RC, MC10 Inc.) were applied to two defined muscle groups for three exercises: a triceps push-up (PU), a biceps curl (BC) and an unweighted squat (US). Methods: Seven healthy volunteers performed three consecutive exercises in the following order; PU, BC, and US. Each exercise was performed for five repetitions with BioStamps applied to the distal and proximal ends of the subjects’ dominant side using adhesive bandages. For each of the defined exercises the investigator played a timed voice recording in which the subjects were instructed to perform the series of repetitions with consistent timing. Sensors automatically upload de-identified data to a tablet device during use. The following parameters are reported from the stamp: electromyographic data (of the muscle causing abduction and adduction) and acceleration (of the distal and proximal ends of the limb which is being abducted/adducted). The data was uploaded to Python and analyzed using a rolling average. P-values were then determined using a one-tailed t-test. Results: Each of the three strength exercises had two identifiable motion signatures, one from each muscle group, derived from the sEMG data which shows the peak muscle activation during the 5 repetitions of an exercise (Figure 1, E). Placement on the BioStamps on the TB and BB recorded activation in the PU and BC (Figure 1, A & B). There is a difference between the TB and BB activation in the PU (p=0.358) but no difference was found between their activation in the BC (p=0.06). This finding was limited by the small sample size (n=7), which would be improved in a future study. Placement of the BioStamps on the BF and RF was used in the unweighted squat (Figure 1, C & D). There is a difference in the RF and BF activation in the US (p=0.179). Discussion: By nature of the antagonistic motion of the triceps brachii (TB) and biceps brachii (BB) in a push-up, activation levels measured by sEMG recordings are expected to be similar. The TB acts as one of the primary movers, while the BB acts as an antagonist and stabilizes the movement to allow for a controlled push-up. Similarly, in a squat similar levels of activation were expected in the rectus femoris (RF) and the biceps femoris (BF) as the RF functions as a primary mover and the BF as a stabilizer. Activation of both the primary mover and stabilizing muscles is important for proper form and function.Figure 1. A & B. Placement of BioStamps on the triceps brachii and biceps brachii, muscles used in the biceps curl (p=0.06) and triceps push-up (p=0.358). C & D. Placement of BioStamps on the rectus femoris and the biceps femoris, muscles used in the unweighted squat (p=0.179). E. Unweighted squat sEMG graph showing muscle activation (mV) of rectus femoris over time (s).

Effect Of Different Grip Position And Shoulder- Abduction Angle On Muscle Strength And Activation During The Seated Cable Row

The purpose of this study was to compare the peak force and electromyographic activation in different techniques of the seated row. Eleven recreationally trained male (28±5 years, 176±5 cm, 94±16 kg) and ten female (27±5 years, 168±8 cm, 65±11 kg ) performed an isometric and a dynamic assessment of the seated cable row and the preacher curl: pronated grip (PRO), supinated grip (SUP), neutral grip (NEU), 30° (30°), 60° (60°), 90° (90°) of shoulder abduction, and cable preacher curl (PC). Peak force and muscle activation of upper trapezius, middle trapezius, upper latissimus, lower latissimus, posterior deltoid, and biceps bracii were recorded during the isometric and dynamic assessment of the exercises. p values&lt;0.05 were considered statistically significant. The peak force was greater when shoulder abduction angle was closer to 0° (PRO, SUP, and NEU) and decreased as abduction angle increased (60° and 90°). Muscle activation of the upper back (upper trapezius, middle trapezius) and posterior deltoid increased as abduction angle increased (60° and 90°) on both isometric and dynamic analysis. Muscle activation of the upper and lower latissimus increased as abduction angle was closer to 0° (PRO, SUP, and NEU) on both isometric and dynamic analysis. Biceps brachii activation on both isometric and dynamic analysis during the PC was greater than all other rowing conditions; among the rowing techniques, BB activation was greater during SUP, NEU, and 90° techniques. In conclusion, the closer to 90° shoulder abduction the greater UT, MT, and PD activity, on the other hand, the closer to 0° shoulder abduction the greater peak force, UL, and LL activity during the variations of the rowing exercise.

Flat Versus Simulated Mountain Trail Running: A Multidisciplinary Comparison in Well-Trained Runners

This paper compares cardiopulmonary and neuromuscular parameters across three running aerobic speeds in two conditions that differed from a treadmill's movement: flat condition (FC) and unpredictable roll variations similar to mountain trail running (URV). Twenty well-trained male runners (age 33 ± 8 years, body mass 70.3 ± 6.4 kg, height 1.77 ± 0.06 m, V˙O2max 63.8 ± 7.2 mL·kg-1·min-1) voluntarily participated in the study. Laboratory sessions consisted of a cardiopulmonary incremental ramp test (IRT) and two experimental protocols. Cardiopulmonary parameters, plasma lactate (BLa-), cadence, ground contact time (GT) and RPE values were assessed. We also recorded surface electromyographic (sEMG) signals from eight lower limb muscles, and we calculated, from the sEMG envelope, the amplitude and width of peak muscle activation for each step. Cardiopulmonary parameters were not significantly different between conditions (V˙O2: p = 0.104; BLa-: p = 0.214; HR: p = 0.788). The amplitude (p = 0.271) and width (p = 0.057) of sEMG activation peaks did not change between conditions. The variability of sEMG was significantly affected by conditions; indeed, the coefficient of variation in peak amplitude (p = 0.003) and peak width (p < 0.001) was higher in URV than in FC. Since the specific physical demands of running can differ between surfaces, coaches should resort to the use of non-traditional surfaces, emphasizing specific surface-related motor tasks that are normally observed in natural running environments. Seeing that the variability of muscle activations was affected, further studies are required to better understand the physiological effects induced by systematic surface-specific training and to define how variable-surface activities help injury prevention.

Activity distribution among the hamstring muscles during high-speed running: A descriptive multichannel surface EMG study.

This study assessed activity distribution among the hamstring muscles during high-speed running. The objective was to compare within and between muscle activity, relative contribution and hip and knee joint angles at peak muscle activity during high-speed running. Through multichannel electromyography, we measured muscle activity in male basketball players during high-speed running on a treadmill at 15 locations: five for biceps femoris long head, four for semitendinosus, and six for semimembranosus. Muscle activity was calculated for each location within each hamstring muscle individually for each percent of a stride cycle. Twenty-nine non-injured basketball players were included (mean age: 17 ± 1 years; mass, 85 ± 9kg; height, 193 ± 9cm). Heterogeneous activity was found for all individual hamstring muscles across multiple events of the stride cycle. In the late-swing phase, muscle activity and relative contribution of the semimembranosus was significantly higher than of the semitendinosus. There was no significant difference in hip and knee joint angles at instant of peak muscle activity, assessed locally within individual hamstring muscles, as well as in general over the whole hamstring muscle. Hamstring muscles were most active in the late-swing phase during high-speed running. In this phase, the semimembranosus was most active and the semitendinosus was least active. Within the biceps femoris long head, the most proximal region was significantly more active in the late-swing phase, compared to other muscle regions. For each muscle and location, peak muscle activity occurred at similar hip and knee joint angles.

Effects of an elastomeric technology garment on different external and internal load variables

Resistance training is one key method for improving physical conditioning. With this purpose, Menatechpro System® has designed an avant-garde garment that includes elastomeric technology that may stimulate the neuromuscular system in a better way, but a deeper knowledge of its effects is needed. Objective: To explore the effects of a new garment with elastomeric technology on upper-limb performance, and neuromuscular, perceptual, and cardiovascular responses in two upper-extremities exercises. Methodology: Fit young men trained in resistance exercises performed a seated shoulder press (80% of one-repetition maximum) and push up (bodyweight) until muscle failure with the garment that incorporates the elastomeric technology versus a placebo garment without it. The number of repetitions, mean propulsive velocity, mean and peak muscle activation, rate of perceived effort and perceived velocity, and heart rate were analysed. Possible differences were obtained with a two-way mixed ANOVA of repeated measures with post-hoc analysis. Results: Compared with a placebo garment, the use of this new garment with elastomeric technology improved positively the physical performance and muscular activation during the exercises analysed (p ≤ .05). Conclusion: Menatechpro System®'s elastomeric technology integrated into the garment could provide an optimal neuromuscular stimulus for the development of the performance during the upper extremity training.

A Self-Aligning Upper-Limb Exoskeleton Preserving Natural Shoulder Movements: Kinematic Compatibility Analysis.

NESM- γ is an upper-limb exoskeleton to train motor functions of post-stroke patients. Based on the kinesiology of the upper limb, the NESM- γ includes a four degrees-of-freedom (DOF) active kinematic chain for the shoulder and elbow, along with a passive chain for self-aligning robotic joint axes with the glenohumeral (GH) joint's center of rotation. The passive chain accounts for scapulohumeral rhythm and trunk rotations. To assess self-aligning performance, we analyzed the kinematic and electromyographic data of the shoulder in eight healthy subjects performing reaching tasks under three experimental conditions: moving without the exoskeleton (baseline), moving while wearing the exoskeleton with the passive DOFs properly functioning, i.e., unlocked (human-in-the-loop(HIL)-unlocked), and with the passive DOFs locked (HIL-locked). Comparison of baseline and HIL-unlocked conditions showed nearly unchanged anatomical movement patterns, with a root-mean-square error of shoulder angle lower than 5 deg and median deviations of the GH center of rotation below 20 mm. Peak muscle activations showed no significant differences. In contrast, the HIL-locked condition deviated significantly from the baseline, as observed by the trunk and GH trajectory deviations up to 50 mm, accompanied by increased peak muscle activations in the Deltoid and Upper Trapezius muscles. These findings highlight the need for kinematic solutions in shoulder exoskeletons that can accommodate the movements of the entire shoulder complex and trunk to achieve kinematic compatibility.

Electromyography of the multifidus muscle in horses trotting over firm and soft surfaces

Equine sports medicine has developed a focus on the multifidus muscle with little reported knowledge of its activity in normal horses. Our main aim and objective was to use in-dwelling electromyography (EMG) to measure and compare the average and peak activity of the multifidus muscle at the level of the 12th (T12) and 18th thoracic (T18) and 5th lumbar (L5) vertebra bilaterally. We hypothesized that trotting horses in hand over a soft deformable surface would cause an increase in both average and peak activity when compared to trotting on a non-deformable asphalt surface. The EMG signals from four horses each with 25 observable muscle contractions at each location were filtered and normalized to the maximum observed signals. The effect of two surface conditions on the average and peak muscle activity within each muscle section of four horses was assessed using unpaired t-tests. The average muscle activity was significantly higher while trotting over a soft surface when compared to the hard asphalt surface in the right T12 (mean difference [MD]=0.13 p < 0.001), right L5 (MD=0.12 p < 0.001) and left L5 (MD=0.18 p < 0.001) regions, although the left T12 location showed significantly higher average activity on the hard surface (MD=0.13 p < 0.001). The peak activity was significantly higher on soft footing in the left T18 (MD=0.10 p < 0.05), left L5 (MD=0.18 p < 0.001), right T12 (MD= 0.40 p < 0.001), and right L5 (MD=0.10 p < 0.001). Therefore, when compared to trotting on a hard surface, the softer surface induced higher levels of muscle activity in most of the multifidi locations.

Comparison between a targeted exercise program and a sham intervention on gluteal muscle activity in people with hip osteoarthritis: Analysis of secondary outcomes from a randomised clinical trial

BackgroundPeople with hip osteoarthritis (OA) typically display altered gluteus minimus (GMin) and gluteus medius (GMed) activity during gait, in addition to reduced walking speed and stride length. It is unknown if current rehabilitation programs address changes in gluteal muscle activity in people with hip OA. Research questionCan a targeted gluteal intervention restore normal gluteal muscle segment activity during gait in people with hip OA? MethodsThis study presents secondary outcomes from a multi-site, double-blinded clinical trial in which participants with radiologically confirmed mild-moderate hip OA were randomised into a targeted gluteal or sham intervention for 12-weeks following baseline testing. Electromyography (EMG) outcomes were only conducted at a single site and data were collected from 22 participants. Intramuscular electrodes were inserted into two segments of GMin (anterior, posterior) and three segments of GMed (anterior, middle, posterior) to record average amplitude, peak amplitude and time to peak (TTP) during the first 60 % of the gait cycle (stance phase) at baseline and post-intervention. ResultsFollowing the targeted gluteal intervention, posterior GMin displayed a decrease in average (P = 0.032, ES=1.04) and peak (P = 0.017, ES=1.17) muscle activity during late stance phase with a shift to an earlier TTP (P = 0.034, ES=1.02). There were no further significant changes between groups for other outcome measures. Similar trends for an earlier TTP were observed for the posterior segment of GMed following the targeted intervention (P = 0.095, ES=0.87). The earlier TTP in the posterior segments of both GMin and GMed post-intervention resembled patterns observed in a healthy young population. SignificanceA targeted gluteal intervention can positively impact activity in posterior GMin during gait in people with hip OA when compared to a sham intervention.

Bench, Bar, and Ring Dips: Do Kinematics and Muscle Activity Differ?

The purpose of this study was to profile and compare the kinematics, using 3D motion capture, and muscle activation patterns, using surface electromyography (sEMG), of three common dip variations; the bench, bar, and ring dips. Thirteen experienced males performed four repetitions of each dip variation. For each participant, repetitions 2–4 were time-normalized and then averaged to produce a mean value for all kinematic and sEMG variables. The mean maximal joint angles and mean peak sEMG amplitudes were compared between each variation using a one-way ANOVA with repeated measures. Several significant differences (p < 0.05) between dip variations were observed in both kinematic and sEMG data. The bench dip predominantly targets the triceps brachii but requires greater shoulder extension range. The mean peak triceps brachii activation was 0.83 ± 0.34 mV on the bench, 1.04 ± 0.27 mV on the bar, and 1.05 ± 0.40 mV on the ring. The bar dip is an appropriate progression from the bench dip due to the higher peak muscle activations. The ring dip had similar peak activations to the bar dip, with three muscles increasing their activation intensities further. These findings have implications for practitioners prescribing the dip, particularly to exercisers with a history of shoulder pain and injury.

Effect of Clenbuterol on Muscle Activity During Exercise in Standardbred Horses

Clenbuterol (β2 agonist) is a commonly administered bronchodilator in race and performance horses. While long-term administration can alter exercise performance and muscle properties, little is known about its effects on these parameters following short-term administration. A single dose of clenbuterol (0.80 µg/kg) was expected to alter muscle activity of the extensor carpi radialis, semitendinosus, and longissimus dorsi during submaximal exercise. Eight mature Standardbred horses exercised for 2 minutes at 5 m/s on a high-speed treadmill following clenbuterol dosing (clenbuterol) or no dosing (control) in a crossover experimental design. Surface electromyography (sEMG) data were collected continuously from the muscles of interest and processed to determine average rectified value (ARV) and median frequency (MF) of the signal during peak muscle activation (100 ms period) during 15 strides. ARV data were log transformed. Data were analyzed with a mixed model ANOVA with fixed effects of period and treatment and a random effect of horse. No differences (P > .05) in amplitude (ARV) or frequency (MF) of the EMG signal were detected following clenbuterol administration. Thus, a one-time dose of clenbuterol had no statistically detectable effect on muscle activity during submaximal exercise. Further studies should be undertaken to confirm these results and examine the effects of long-term administration on muscle activity during exercise.

Detection thresholds for electrostimulation combined with robotic leg support in sub-acute stroke patients.

Stroke is one of the leading causes of disability in adults in the European Union. It often leads to motor impairments, such as a hemiparetic lower extremity. Research indicates that early task-specific and intensive training promotes neuroplasticity and leads to recovery and/or compensation. One way to provide intensive training early after a stroke is via robot-supported training. A rehabilitation robot was designed by Life Science Robotics (Aalborg, Denmark) that can provide continuous repetitive movements of the hip, knee, and/or ankle in e.g., a lying position. In order to emphasize active contribution by the patient, actively triggered electrical stimulation (via muscle activation) can be combined with robotic assistance. The current study aims to compare different threshold estimation methods for detection of movement intention from muscle activity for actively triggered electrical stimulation during robot-supported leg movement in stroke patients. Three sub-acute stroke patients were included for a single measurement session. They performed knee extension and/or ankle dorsal flexion with four different threshold estimation methods to assess the intention detection threshold to initiate electrostimulation. The thresholds were based on the resting level of muscle activity (of m. rectus femoris or m. tibialis anterior) plus two or three times the standard deviation of the average resting value, or the resting level plus 5% or 10% of the peak muscle activity during a maximal voluntary contraction. The results showed that the method based on the resting muscle activity plus two times the standard deviation was the most stable across the three included stroke patients. This method had a detection success rate of 86.7% and was experienced as moderately comfortable. In conclusion, performing knee extension and/or ankle dorsal flexion with electromyography triggered electrostimulation is feasible in sub-acute stroke patients. Muscle activity-triggered electrostimulation combined with robotic support based on a threshold of resting levels plus two times the standard deviation seems to detect movement initiation most consistently in this small sample of sub-acute stroke patients.

Enhancing Voluntary Motion with Modular, Backdrivable, Powered Hip and Knee Orthoses.

Mobility disabilities are prominent in society with wide-ranging deficits, motivating modular, partial-assist, lower-limb exoskeletons for this heterogeneous population. This paper introduces the Modular Backdrivable Lower-limb Unloading Exoskeleton (M-BLUE), which implements high torque, low mechanical impedance actuators on commercial orthoses with sheet metal modifications to produce a variety of hip- and/or knee-assisting configurations. Benchtop system identification verifies the desirable backdrive properties of the actuator, and allows for torque prediction within ±0.4 Nm. An able-bodied human subject experiment demonstrates that three unilateral configurations of M-BLUE (hip only, knee only, and hip-knee) with a simple gravity compensation controller can reduce muscle EMG readings in a lifting and lowering task relative to the bare condition. Reductions in mean muscular effort and peak muscle activation were seen across the primary squat musculature (excluding biceps femoris), demonstrating the potential to reduce fatigue leading to poor lifting posture. These promising results motivate applications of M-BLUE to additional populations, and the expansion of M-BLUE to bilateral and ankle configurations.

Dual-Motor Balance Tasks Prompts Slight Lower Limb Neuromuscular Adaptations in Healthy Young Adults

Previous literature has analyzed muscular recruitment patterns in various populations during complex balance conditions that involve a secondary task. This inquiry seeks to determine whether challenging sensory systems in young adults during single and dual-motor tasks can prompt modifications in neuromuscular patterns at the hip and leg musculature. Our study included twenty-nine healthy young adults (3 males and 25 females) with an average age of 24.3+/-2.4. Electromyography (EMG) electrodes were used to collect EMG data, and the variables of interest include the onset of muscle contraction, the decay of muscle contraction, peak muscle activation, and duration of muscle contraction. Five balance activities were conducted while performing a dual-motor task, while sensory input was altered in each condition. No significant changes in EMG activity were observed in the gastrocnemius (GA) and (TA) muscle activity. However, a tendency was observed in the onset and duration values of the gluteal muscles. Recruitment of the TA and GA remained uniform across variables, but gluteus maximus (GMax) and medius (GMed) activity appeared sooner (onset) and lasted longer (duration). Comparability in muscle recruitment during dual-task balance activities indicates healthy young adults can successfully rely on other sensory systems for balance when one or more networks are altered. Increases in GA and TA activity suggested a greater need for ankle strategies during the condition trials, while increased GMax and GMed activity indicated the same for hip strategies. Further research should examine joint kinematic to discern any adaptations during dual-motor tasks in young, healthy adults.

Electromyography of the Multifidus Muscle in Horses Trotting During Therapeutic Exercises.

Thoracolumbar pain has been identified in both human and equine patients. Rehabilitation and conditioning programs have focused specifically on improving trunk and abdominal muscle function (1–5). Equine exercise programs routinely incorporate ground poles and training devices for the similar goals of increasing spinal and core stability and strength (6–8). The multifidus muscle has been an area of focus due to atrophy associated with disease (9). To date, there have been no reports on the activity of the multifidus muscle in horses in relation to therapeutic exercises. Our objectives were to use electromyography to determine the average work performed and peak muscle activity of the multifidus in horses trotting, trotting over ground poles, trotting while wearing a resistance band-based training device and trotting while wearing the training device over ground poles. We hypothesized that ground poles and the training device would each increase average work performed and peak multifidus muscle activity. Right and left cranial thoracic locations showed significant increased muscle work and peak activation when horses were trotted over ground poles versus without. The peak activation was significantly greater in horses trotting over poles in both lumbar regions, but there was no significant change in peak activation in either location due to the training device. When the influence of the training device was investigated without ground poles, left caudal thoracic muscle work and peak activity, and right lumbar muscle work were significantly lower when using the training device, as compared to without. When the training device was combined with trotting over ground poles, both left and right caudal thoracic regions showed significantly lower muscle work and peak activity when the device was used. There was no significant difference between with and without the device in either left or right lumbar muscle work. In conclusion, implementing ground poles can be an effective strategy to increase the activation of the multifidus muscle, however, caution should be taken when incorporating the use of a resistance band training device as muscle work and peak activation were significantly reduced in most locations. Further study should be performed in regards to the training device to determine its effects on epaxial musculature.

Band Pull-Apart Exercise: Effects of Movement Direction and Hand Position on Shoulder Muscle Activity.

Background/PurposeThe Elastic band pull-apart exercise is commonly used in rehabilitation. It involves pulling an elastic resistance band with both hands in horizontal abduction or diagonal arm movements. The extent of muscle activation during this exercise is unknown. The purpose of this study was to measure the electromyographic (EMG) activity of shoulder-girdle muscles during the pull-apart exercise using resistance bands and to determine the effects of arm position and movement direction on shoulder-girdle muscle activity.Materials/MethodsSurface EMG activity was measured on the infraspinatus, upper trapezius, middle trapezius, lower trapezius and posterior deltoid of the dominant shoulder. After measurement of maximal voluntary contraction (MVC) for each muscle, subjects performed the band pull-apart exercise in three hand positions (palm up, neutral, palm down) and three movement directions (diagonal up, horizontal, diagonal down). Elastic band resistance was chosen to elicit moderate exertion (5/10 on the Borg CR10 scale). The order of the exercises was randomized and three repetitions of each exercise were performed. Mean peak EMG activity in each muscle across the repetitions was calculated and expressed as a percentage of MVC. Peak normalized EMG activity in each muscle was compared in two-way (hand position x direction) repeated-measures ANOVA.ResultsData were collected from 10 healthy subjects (all males, age 36±12 years). Peak muscle activity ranged from 15.3% to 72.6% of MVC across muscles and exercise conditions. There was a significant main effect of hand position for the infraspinatus and lower trapezius, where muscle activity was highest with the palm up hand position (p < 0.001), and for the upper trapezius and posterior deltoid, where muscle activity was highest with the palm down position (p-value range < 0.001-0.004). There was a significant main effect of movement direction, where the diagonal up direction demonstrated the highest muscle activity for the infraspinatus, upper trapezius, lower trapezius, and posterior deltoid (p-value range < 0.001-0.02).ConclusionAltering hand position and movement direction during performance of an elastic band pull-apart exercise can affect magnitudes of shoulder-girdle muscle activity. Clinicians may alter a patient’s hand position and movement direction while performing the band pull-apart exercise in order to increase muscle activity in target muscles or diminish muscle activity in other muscles.Level of Evidence2b

The WATER study: Which AquaTic ExeRcises increase muscle activity and limit pain for people with low back pain?

ObjectiveAquatic exercise therapy is used for the treatment and management of chronic low back pain (CLBP). However, to the authors’ knowledge, no studies to date have compared muscle activity between different aquatic exercises performed by people with CLBP. As such, this study assessed and compared muscle activity, pain, perceived exertion and exercise intensity between different rehabilitative aquatic exercises. DesignCross-sectional. SettingA 25-m indoor swimming pool within a university building. ParticipantsTwenty participants with non-specific CLBP. AssessmentTwenty-six aquatic exercises in shallow water (1.25-m depth). Muscle activity was quantified bilaterally for the erector spinae, multifidus, gluteus maximus and medius, rectus abdominis, and external and internal obliques. Main outcomesMean and peak muscle activity, pain (visual analogue scale), perceived exertion (Borg scale) and exercise intensity (heart rate). ResultsHip abduction/adduction and extension/flexion exercises produced higher activity for gluteal muscles. Variations of squat exercises increased the activity of back extensors. Higher abdominal muscle activity was produced with exercises that made use of buoyancy equipment and included leg and trunk movements while floating on the back, and with some proprioceptive and dynamic lower limb exercises. Pain occurrence and intensity were very low, with 17 exercises being pain free. ConclusionsThis study provides evidence on trunk and gluteal muscle activity, pain, intensity and perceived exertion for people with CLBP performing aquatic exercises. The findings may be useful when prescribing exercises for rehabilitation, as physiotherapists seek to implement progression in effort and muscle activity, variation in exercise type, and may wish to target or avoid particular muscles. Contribution of the Paper•This is the first study to compare trunk or gluteal muscle activity between 26 different aquatic rehabilitative exercises performed by people with CLBP.•Pain occurrence and intensity of aquatic exercises are very low, with most exercises being completely pain free.•The following aquatic exercises are particularly effective in increasing muscle activity: (a) hip abduction/adduction and extension/flexion exercises for gluteus maximus and medius; (b) squat exercises for back extensors (erector spinae and multifidus); and (c) exercises that make use of support buoyancy equipment and include leg movements while floating on the back for abdominals (rectus abdominis, and external and internal obliques).

Evaluation of vertical and multi-axial suspension seats for reducing vertical-dominant and multi-axial whole body vibration and associated neck and low back joint torque and muscle activity

The primary aim of this laboratory-based human subject study was to evaluate the biomechanical loading associated with mining vehicles’ multi-axial whole body vibration (WBV) by comparing joint torque and muscle activity in the neck and low back during three vibration conditions: mining vehicles’ multi-axial, on-road vehicles’ vertical-dominant, and no vibration. Moreover, the secondary aim was to determine the efficacy of a vertical passive air suspension and a prototype multi-axial active suspension seat in reducing WBV exposures and associated biomechanical loading measures. The peak joint torque and muscle activity in the neck and low back were higher when exposed to multi-axial vibration compared to the vertical-dominant or no vibration condition. When comparing the two suspension seats, there were limited differences in WBV, joint torque, and muscle activity. These results indicate that there is a need to develop more effective engineering controls to lower exposures to multi-axial WBV and related biomechanical loading. Practitioner Summary: This study found that mining vehicles’ multi-axial WBV can increase biomechanical loading in the neck and back more so than on-road vehicles’ vertical-dominant WBV. While a newly-developed multi-axial active suspension seat slightly reduced the overall WBV exposures, the results indicate that more effective engineering controls should be developed. Abbreviation: APDF: amplitude probability density function; Aw: weighted average vibration; BMI: body mass index; C7: The 7th cervical vertebra; EMG: electromyography; ES: erector spinae; IRB: institutional review board; ISO: International Organization for Standardization; L5/S1: the fifth lumbar vertebra (L5)/the first sacral vertebra(S1); MSDs: musculoskeletal disorders; MVC: maximum voluntary contraction; PSD: power spectral density; RVC: reference voluntary contraction; SCM: sternocleidomastoid; SD: standard deviation; SPL: splenius capitis; TRAP: trapezius; VDV: vibration dose value; WBV: whole body vibration