Trunk Muscle Activation at the Initiation and Braking of Bilateral Shoulder Flexion Movements of Different Amplitudes

DEEP NECK FLEXORS IMPACT RECTUS ABDOMINIS MUSCLE ACTIVITY DURING ACTIVE STRAIGHT LEG RAISING

Background

Active straight leg raising (ASLR) is commonly performed to test fundamental movement competency. Head control or positioning can affect the abdominal muscle activity during movements.

Purpose

To investigate whether abdominal muscle activity differs when the head is extended or when deep neck flexor (DNF) muscles are selectively activated during the ASLR.

Study Design

Cross-sectional.

Methods

Participants were included based on the following criteria: 1) age>17 years; 2) no spinal or lower extremity pain in the prior month; 3) the vertical line of the malleolus in an elevated the lower limb resides below the knee joint line of a non-moving lower limb during ASLR and above during a passive straight leg raising in each lower limb; and 4) no history of diagnosed spinal deformities or central nervous system disorders. Participants with > 39% reference voluntary contraction in the sternocleidomastoid muscle during the craniocervical flexion test (CCFT) of 24 mmHg target were excluded from the analyses. Right ASLR was repeated in each of the following three head conditions in a random order: 1) neutral head position, 2) head extended by 25 °, and 3) CCFT maintained with a 24 mmHg target. Among the three head conditions, the relative latency for the onset of the right rectus femoris (RF) muscle during the right ASLR and the muscle activity amplitude for 50ms were compared after the onset of RF muscular activity in the following muscles: left rectus abdominis (RA), bilateral external obliques, bilateral internal obliques, and left gluteus maximus muscles.

Results

Data from 31 participants (21 women and 10 men, mean age=22.5 years) were analyzed. The relative latency of the left RA (Hedges' g = 0.39, p=.038) was higher in the CCFT condition (mean±SD=112.1ms±86.0ms) than that in the neutral head condition (82.9ms±58.6ms). However, no difference (all p>.05) was observed in other measures between the groups.

Conclusion

In people with impaired movement competency in ASLR, head extension did not alter the abdominal muscle activities in ASLR. However, selective activation of the DNF muscles delayed the onset of RA muscle activity during the ASLR.

Level of Evidence

4.

Regional activation in the human longissimus thoracis pars lumborum muscle

KEY POINTS

•Longissimus activity in the lumbar region was measured using indwelling electromyography to characterize the territory of its motor units. •The distribution of motor units in the longissimus pars lumborum muscle was mainly grouped into two distinct regions. •Regional activation of the longissimus pars lumborum was also observed during functional tasks involving trunk movements. •The regional activation of the longissimus pars lumborum muscle may play a role in segmental stabilization of the lumbar spine.

ABSTRACT

The longissimus pars lumborum contributes to lumbar postural control and movement. While animal studies suggest a segmental control of this muscle, the territory of motor units constituting the human longissimus pars lumborum remains unknown. The aims of this study were to identify the localization of motor unit territories in the longissimus and assess the activation of this muscle during functional tasks. Eight healthy participants were recruited. During isometric back extension contractions, single motor-unit (at L1, L2, L3 and L4) and multi-unit indwelling recordings (at L1, L1-L2, L2, L2-L3, L3, L3-L4 and L4) were used to estimate motor unit territories in the longissimus pars lumborum based on the motor-unit spike-triggered averages from fine-wire electrodes. A series of functional tasks involving trunk and arm movements were also performed. A total of 73 distinct motor units were identified along the length of the longissimus: only two motor units spanned all recording sites. The majority of the recorded motor units had muscle fibres located in two main rostro-caudal territories (32 motor units spanned L1 to L3 and 30 spanned ∼L3 to L4) and 11 had muscle fibres outside these two main territories. We also observed distinct muscle activation between the rostral and caudal regions of the longissimus pars lumborum during a trunk rotation task. Our results show clear rostral and caudal motor unit territories in the longissimus pars lumborum muscle and suggest that the central nervous system can selectively activate regions of the superficial lumbar muscles to provide local stabilization of the spine.

The onset of deep abdominal muscles activity during tasks with different trunk rotational torques in subjects with non-specific chronic low back pain

BACKGROUND

Although delayed onset of the deep abdominal muscles activity in subjects with non-specific chronic low back pain (CLBP) has been suggested to be related to trunk rotational torque, no study has examined the onsets associated with non-specific CLBP during a variety of tasks with different trunk rotational torque. The aim of this study is to compare the onsets of deep abdominal muscles activity among tasks with different trunk rotational torques in subjects with and without non-specific CLBP.

METHODS

Twelve subjects with non-specific CLBP and 13 control subjects were included. They performed 8 types of upper limb movements. The onsets of muscular activity of bilateral internal oblique-transversus abdominis (IO-TrA) and trunk rotational torque due to the upper limb movements were measured using a surface electromyography and a three-dimensional motion analysis system.

RESULTS

In non-specific CLBP group, right IO-TrA activities were significantly delayed during tasks with left trunk rotational torque compared with the control (P < 0.05), while onsets of the left IO-TrA activities were significantly later than those of the control during tasks with right rotational torque of the trunk (P < 0.05). There were no significant differences in onsets of both sides IO-TrA during tasks without trunk rotational torque between non-specific CLBP and control groups (P > 0.05).

CONCLUSIONS

The onsets of IO-TrA activities in subjects with non-specific CLBP were delayed during tasks with rotational torque of the trunk in the opposite direction, suggesting a possibility that delayed onset of the deep abdominal muscles during rotational torque of the trunk might be etiology of chronic low back pain.

Detection of Infantile Movement Disorders in Video Data Using Deformable Part-Based Model

Movement analysis of infants' body parts is momentous for the early detection of various movement disorders such as cerebral palsy. Most existing techniques are either marker-based or use wearable sensors to analyze the movement disorders. Such techniques work well for adults, however they are not effective for infants as wearing such sensors or markers may cause discomfort to them, affecting their natural movements. This paper presents a method to help the clinicians for the early detection of movement disorders in infants. The proposed method is marker-less and does not use any wearable sensors which makes it ideal for the analysis of body parts movement in infants. The algorithm is based on the deformable part-based model to detect the body parts and track them in the subsequent frames of the video to encode the motion information. The proposed algorithm learns a model using a set of part filters and spatial relations between the body parts. In particular, it forms a mixture of part-filters for each body part to determine its orientation which is used to detect the parts and analyze their movements by tracking them in the temporal direction. The model is represented using a tree-structured graph and the learning process is carried out using the structured support vector machine. The proposed framework will assist the clinicians and the general practitioners in the early detection of infantile movement disorders. The performance evaluation of the proposed method is carried out on a large dataset and the results compared with the existing techniques demonstrate its effectiveness.

Are simultaneous postural adjustments (SPA) programmed as a function of pointing velocity?

This paper deals with the influence of velocity on the postural adjustments that occur during the course of a voluntary movement, that is to say, simultaneous postural adjustments (SPA). To this aim, a pointing task performed at different velocities (V) was considered. Upper limb kinematics and body kinetics were recorded. Using a 2-DOF model, the body was divided into two parts: the right upper limb (termed the "focal" chain) and the rest of the body (termed the "postural" chain). This model allowed us to calculate the kinetics of both subsystems (-F x and [Formula: see text]), with one corresponding to the resultant action on the shoulder (AoSh: -F x) and the other to the resultant reaction of the shoulder (RoSh: [Formula: see text]). The influence of pointing velocity on peak amplitudes and durations was evaluated, as was their instantaneous relationship ("Lissajous ellipse"). The results showed that RoSh and AoSh display similar diphasic profiles, whose amplitude and duration vary with movement velocity. In addition, RoSh is in phase advance of AoSh, the advance being all the shorter as the focal movement velocity becomes faster. Finally, SPA appears to play a dual role, which includes a propulsive action during upper limb acceleration and body stabilization during deceleration. These new findings strengthen the hypothesis that the postural chain is programmed according to task velocity in the same way as the focal chain and that both are coping in order to make the task more efficient.