Effects of increased end-expiratory lung volume on breathing in awake ponies

We studied the changes in breathing and respiratory muscle electromyograms (EMG) during passively induced increases in end-expiratory lung volume (EELV) in awake normal (N), hilar nerve-denervated (HND), carotid body-denervated (CBD), and HND + CBD ponies. EELV was increased by applying continuous negative pressure (-10 and -20 cmH2O) around the torso of the standing pony. In all groups, negative pressure produced sustained increases in EELV that were linearly related to the degree of negative pressure. Elevated EELV decreased breathing frequency (f) in N and CBD ponies but increased f in HND and HND + CBD ponies. When EELV was increased, tidal volume was unchanged or above control in N ponies but was below or near control in the other groups. In all groups during elevated EELV, arterial PCO2 initially decreased but then increased relative to control with isocapnia achieved after approximately 1.5 min. In all groups, the elevated EELV was accompanied by increased stimulation of the diaphragm as indicated by increased rate of rise of the integrated EMG (P less than 0.05). During elevated EELV, the duration of diaphragm EMG was reduced, but only in HND ponies was this reduction significant (P less than 0.05). In N ponies, the major effect of elevated EELV on the expiratory transversus abdominis (TA) muscle was an increase (P less than 0.05) in duration of activity and therefore total activity. The work of breathing was thus presumably shifted more to this muscle during elevated EELV. These changes in TA timing were not observed in HND and HND + CBD ponies during elevated EELV. We conclude that elevation of EELV, which presumably places the diaphragm on a less favorable portion of its length-tension relationship, results in compensatory increased stimulation of the diaphragm that is not critically dependent on hilar and carotid chemoreceptor afferents. However, hilar afferents do contribute to the changes in diaphragm and TA duration of activity during elevated EELV.     

Electrical activation of expiratory muscles increases with time in pentobarbital-anesthetized dogs.

Although the pentobarbital-anesthetized dog is often used as a model in studies of respiratory muscle activity during spontaneous breathing, there is no information regarding the stability of the pattern of breathing of this model over time. The electromyograms of several inspiratory and expiratory muscle groups were measured in six dogs over a 4-h period by use of chronically implanted electrodes. Anesthesia was induced with pentobarbital sodium (25 mg/kg iv), with supplemental doses to maintain constant plasma pentobarbital concentrations. Phasic electrical activity increased over time in the triangularis sterni, transversus abdominis, and external oblique muscles (expiratory muscles). The electrical activity of the costal diaphragm, crural diaphragm, and parasternal intercostal muscles (inspiratory muscles) was unchanged. These changes in electrical activity occurred despite stable plasma levels of pentobarbital and arterial PCO2. They were associated with changes in chest wall motion and an increased tidal volume with unchanged breathing frequency. We conclude that expiratory muscle groups are selectively activated with time in pentobarbital-anesthetized dogs lying supine. Therefore the duration of anesthesia is an important variable in studies using this model.     

Slow expiration reduces sternocleidomastoid activity and increases transversus abdominis and internal oblique muscle activity during abdominal curl-up

The aim of this study was to investigate the effects of quiet inspiration versus slow expiration on sternocleidomastoid (SCM) and abdominal muscle activity during abdominal curl-up in healthy subjects. Twelve healthy subjects participated in this study. Surface electromyography (EMG) was used to collect activity of bilateral SCM, rectus abdominis (RA), external oblique (EO), and transversus abdominis/internal oblique (TrA/IO) muscles. A paired t-test was used to determine significant differences in the bilateral SCM, RF, EO, and TrA/IO muscles between abdominal curl-up with quiet inspiration and slow expiration. There were significantly lower EMG activity of both SCMs and greater EMG activity of both IOs during abdominal curl-up with slow expiration, compared with the EMG activity of both SCMs and IOs during abdominal curl-up with quiet inspiration (p < .05). The results of this study suggest that slow expiration would be recommended during abdominal curl-up for reduced SCM activation and selective activation of TrA/IO in healthy subjects compared with those in abdominal curl up with quiet inspiration.     

Vagal contributions to respiratory muscle activity during eupnea in the awake dog.

We examined the effects of reversible vagal cooling on respiratory muscle activities in awake chronically instrumented tracheotomized dogs. We specifically analyzed electromyographic (EMG) activity and its ventilatory correlates, end-expiratory lung volume (EELV) and diaphragmatic resting length via sonomicrometry. Elimination of phasic and tonic mechanoreceptor activity by vagal cooling doubled the EMG activity of the costal, crural, and parasternal muscles, with activation occurring sooner relative to the onset of inspiratory flow. Diaphragmatic postinspiration inspiratory activity in the intact dog coincided with a brief mechanical shortening of the diaphragm during early expiration; vagal blockade removed both the electrical activity and the mechanical shortening. Vagal blockade also doubled the EMG activity of a rib cage expiratory muscle, the triangularis sterni, but reduced that of an abdominal expiratory muscle, the transversus abdominis. Within-breath electrical activity of both muscles occurred sooner relative to the onset of expiratory flow during vagal blockade. Vagal cooling was also associated with a 12% increase in EELV and a 5% decrease in end-expiratory resting length of the diaphragm. We conclude that vagal input significantly modulates inspiratory and expiratory muscle activities, which help regulate EELV efficiently and optimize diaphragmatic length during eupneic breathing in the awake dog.     

Transversus abdominis muscle function in humans

We used a high-resolution ultrasound to make electrical recordings from the transversus abdominis muscle in humans. The behavior of this muscle was then compared with that of the external oblique and rectus abdominis in six normal subjects in the seated posture. During voluntary efforts such as expiration from functional residual capacity, speaking, expulsive maneuvers, and isovolume "belly-in" maneuvers, the transversus in general contracted together with the external oblique and the rectus abdominis. In contrast, during hyperoxic hypercapnia, all subjects had phasic expiratory activity in the transversus at ventilations between 10 and 18 l/min, well before activity could be recorded from either the external oblique or the rectus abdominis. Similarly, inspiratory elastic loading evoked transversus expiratory activity in all subjects but external oblique activity in only one subject and rectus abdominis activity in only two subjects. We thus conclude that in humans 1) the transversus abdominis is recruited preferentially to the superficial muscle layer of the abdominal wall during breathing and 2) the threshold for abdominal muscle recruitment during expiration is substantially lower than conventionally thought.     

The effect of posture on respiratory activity of the abdominal muscles

The purpose of this study was to determine the influence of posture on the expiratory activity of the abdominal muscles. Fifteen young adult men participated in the study. Activities of the external oblique abdominis, internal oblique abdominis, and rectus abdominis muscles were measured electromyographically in various postures. We used a pressure threshold in order to activate the abdominal muscles as these muscles are silent at rest. A spirometer was used to measure the lung volume in various postures. Subjects were placed in the supine, standing, sitting, and sitting-with-elbow-on-the-knee (SEK) positions. Electromyographic activity and mouth pressure were measured during spontaneous breathing and maximal voluntary ventilation under the respiratory load. We observed that the lung volume changed with posture; however, the breathing pattern under respiratory load did not change. During maximal voluntary ventilation, internal oblique abdominis muscle expiratory activity was lower in the SEK position than in any other position, external oblique abdominis muscle inspiratory activity was lower in the supine position than in any other position, and internal oblique abdominis muscle activity was higher in the standing position than in any other position. During spontaneous breathing, external oblique abdominis muscle activity was higher during expiration and inspiration in the SEK position than in any other position. The internal oblique abdominis muscle activity was higher during both inspiration and expiration in the standing position than in any other position. The rectus abdominis muscle activity did not change with changes in posture during both inspiration and expiration. Increase in the external oblique abdominis activity in the SEK position was due to anatomical muscle arrangement that was consistent with the direction of lower rib movement. On the other hand, increase in the internal oblique abdominis activity in the standing position was due to stretching of the abdominal wall by the viscera. We concluded that differences in activity were due to differences in the anatomy of the abdominal muscles and the influence of gravity.     

Integrated approach for in vivo evaluation of respiratory muscles mechanics

The respiratory muscles constitute the respiratory pump, which determines the efficacy of ventilation. Any functional disorder in their performance may cause insufficient ventilation. This study was designed to quantitatively explore the relative contribution of major groups of respiratory muscles to global lung ventilation throughout a range of maneuvers in healthy subjects. A computerized experimental system was developed for simultaneous noninvasive measurement of inspired/expired airflow, mouth pressure and up to 8 channels of EMG surface signals from major respiratory muscles which are located near the skin (e.g., sternomastoid, external intercostal, rectus abdominis and external oblique) during various respiratory maneuvers. Lung volumes values were calculated by integration of airflow data. Hill's muscle model was utilized to calculate the forces generated by the muscles from the acquired EMG data. Analysis of EMG measurements and respiratory muscles forces revealed the following characteristics: (a) muscle activity increased with increased breathing effort, (b) inspiratory muscles contributed to inspiration even at relatively low flow rates, while expiratory muscles are recruited at higher flow rates, (c) the forces generated by the muscle depended on the muscle properties as well as on their EMG performance and (d) the pattern of the muscle's force curves varied between subjects, but were generally consistent for the same subject regardless of breathing effort.     

Differential timing of respiratory muscles in response to chemical stimuli in awake dogs

We assessed changes in respiratory muscle timing in response to hyperpnea and shortened inspiratory and expiratory times caused by chemoreceptor stimuli in six awake dogs. Durations of postinspiratory inspiratory activity of costal and crural diaphragm (PIIA), the delay in diaphragm electromyogram (EMG) after the initiation of inspiratory airflow, postexpiratory expiratory activity of the transversus abdominis (PEEA), and the delay of abdominal expiratory muscle activity after the initiation of expiratory airflow were measured. In control, four out of six dogs showed PIIA [8-10% of expiratory time (TE)]; all showed delay of diaphragm [19% of inspiratory time (TI)], delay of abdominal muscle activation (21% of TE), and PEEA (24% of TI). Hypercapnia decreased PIIA (4-9% of TE), maintained diaphragm delay at near control values (23% of TI), increased PEEA (36% of TI), eliminated delay of abdominal muscle activation (4% of TE), and decreased end-expiratory lung volume (EELV). Hypocapnic hypoxia increased PIIA (24-25% of TE), eliminated diaphragm delay (3% of TI), eliminated PEEA (3% of TI), reduced delay of abdominal muscle activation (14% of TE), and increased EELV. Most of these effects of hypoxic hypocapnia vs. hypercapnia on the within-breath EMG timing parameters corresponded to differences in the magnitude of expiratory muscle activation. These changes exerted significant influences on flow rates and EELV.     

Regulation of end-expiratory lung volume during exercise

We determined the effects of exercise on active expiration and end-expiratory lung volume (EELV) during steady-state exercise in 13 healthy subjects. We also addressed the questions of what affects active expiration during exercise. Exercise effects on EELV were determined by a He-dilution technique and verified by changes in end-expiratory esophageal pressure. We also used abdominal pressure-volume loops to determine active expiration. EELV was reduced with increasing exercise intensity. EELV was reduced significantly during even mild steady-state exercise and during heavy exercise decreased an average of 0.71 +/- 0.3 liter. Dynamic lung compliance was reduced 30-50%; EELV remained greater than closing volume. Changing the resistance to airflow (via SF6-O2 or He-O2 breathing) during steady-state exercise changed the peak gastric and esophageal pressure generation during expiration but did not alter EELV; breathing through the mouthpiece produced similar effects during exercise. EELV was significantly reduced in the supine position. With supine exercise active expiration was not elicited, and EELV remained the same as in supine rest. With CO2-driven hyperpnea (7-70 l/min), EELV remained unchanged from resting levels, whereas during exercise, at similar minute ventilation (VE) values EELV was consistently decreased. At the same VE, treadmill running caused an increase in tonic gastric pressure and greater reductions in EELV than either walking or cycling. We conclude that both the exercise stimulus and the resultant hyperpnea stimulate active expiration and a reduced FRC. This new EELV is preserved in the face of moderate changes in mechanical time constants of the lung. This reduced EELV during exercise aids inspiration by optimizing diaphragmatic length and permitting elastic recoil of the chest wall.     

Chest wall distortion during resistive inspiratory loading

We studied six (1 naive and 5 experienced) subjects breathing with added inspiratory resistive loads while we recorded chest wall motion (anteroposterior rib cage, anteroposterior abdomen, and lateral rib cage) and tidal volumes. In the five experienced subjects, transdiaphragmatic and pleural pressures, and electromyographs of the sternocleidomastoid and abdominal muscles were also measured. Subjects inspired against the resistor spontaneously and then with specific instructions to reach a target pleural or transdiaphragmatic pressure or to maximize selected electromyographic activities. Depending on the instructions, a wide variety of patterns of inspiratory motion resulted. Although the forces leading to a more elliptical or circular configuration of the chest wall can be identified, it is difficult to analyze or predict the configurational results based on insertional and pressure-related contributions of a few individual respiratory muscles. Although overall chest wall respiratory motion cannot be readily inferred from the electromyographic and pressure data we recorded, it is clear that responses to loading can vary substantially within and between individuals. Undoubtedly, the underlying mechanism for the distortional changes with loading are complex and perhaps many are behavioral rather than automatic and/or compensatory.     

Effect of instruction,surface stability,and load intensity on trunk muscle activity

The aim of this study was to assess the effect of verbal instruction, surface stability, and load intensity on trunk muscle activity levels during the free weight squat exercise. Twelve trained males performed a free weight squat under four conditions: (1) standing on stable ground lifting 50% of their 1-repetition maximum (RM), (2) standing on a BOSU balance trainer lifting 50% of their 1-RM, (3) standing on stable ground lifting 75% of their 1-RM, and (4) receiving verbal instructions to activate the trunk muscles followed by lifting 50% of their 1-RM. Surface EMG activity from muscles rectus abdominis (RA), external oblique (EO), transversus abdominis/internal oblique (TA/IO), and erector spinae (ES) were recorded for each condition and normalized for comparisons. Muscles RA, EO, and TA/IO displayed greater peak activity (39–167%) during squats with instructions compared to the other squat conditions (P = 0.04–0.007). Peak EMG activity of muscle ES was greater for the 75% 1-RM condition than squats with instructions or lifting 50% of 1-RM (P = 0.04–0.02). The results indicate that if the goal is to enhance EMG activity of the abdominal muscles during a multi-joint squat exercise then verbal instructions may be more effective than increasing load intensity or lifting on an unstable surface. However, in light of other research, conscious co-activation of the trunk muscles during the squat exercise may lead to spinal instability and hazardous compression forces in the lumbar spine.     

Differential respiratory muscle recruitment induced by clonidine in awake goats

The purpose of this study was to test thehypothesis that dysrhythmic breathing induced by the₂-agonist clonidine isaccompanied by differential recruitment of respiratory muscles. Inadult goats (n = 14) electromyographic(EMG) measurements were made from inspiratory muscles (diaphragm andparasternal intercostal) and expiratory muscles [triangularissterni (TS) and transversus abdominis (Abd)]. EMG of thethyroarytenoid (TA) muscle was used as an index of upper airway(glottal) patency. Peak EMG activities of all spinal inspiratory andexpiratory muscles were augmented by central and peripheralchemoreceptor stimuli. Phasic TA was apparent in the postinspiratoryphase of the breathing cycle under normoxic conditions. Duringdysrhythmic breathing episodes induced by clonidine, TS and Abdactivities were attenuated or abolished, whereas diaphragm andparasternal intercostal activities were unchanged. There was no tonicactivation of TS or Abd EMG during apneas; however, TA activity becametonic throughout the apnea. We conclude that1) ₂-adrenoceptor stimulationresults in differential recruitment of respiratory muscles duringrespiratory dysrhythmias and 2) apneas are accompanied by active glottic closure in the awake goat.

     

Inhomogeneous response of expiratory muscle activity to cold block of the ventral medullary surface.

We assessed the effects of cooling the ventral medullary surface (VMS) on the activity of chest wall and abdominal expiratory muscles in eight anesthetized artificially ventilated dogs after vagotomy and denervation of the carotid sinus nerves. Electromyograms (EMGs) of the triangularis sterni, internal intercostal, abdominal external oblique, abdominal internal oblique, and transversus abdominis muscles were measured with EMG of the diaphragm as an index of inspiratory activity. Bilateral localized cooling (2 x 2 mm) in the thermosensitive intermediate part of the VMS produced temperature-dependent reduction in the EMG of diaphragm and abdominal muscles. The rib cage expiratory EMGs were little affected at 25 degrees C; their amplitudes decreased at lower VMS temperatures (less than 20 degrees C) but by significantly fewer degrees than the diaphragmatic and abdominal expiratory EMGs at a constant VMS temperature. With moderate to severe cooling (less than 20 degrees C) diaphragmatic EMG disappeared, but rib cage expiratory EMGs became tonic and resumed a phasic pattern shortly before the recovery of diaphragmatic EMG during rewarming of the VMS. These results indicate that the effects of cooling the VMS differ between the activity of rib cage and abdominal expiratory muscles. This variability may be due to inhomogeneous inputs from the VMS to expiratory motoneurons or to a different responsiveness of various expiratory motoneurons to the same input either from the VMS or the inspiratory neurons.     

Oxygen cost of resistive-loaded breathing in quadriplegia.

We hypothesized that, in quadriplegia, chest wall distortion would increase the energy cost of ventilation. To assess this, we measured the oxygen cost of breathing (VO2 resp) and changes in chest wall configuration during inspiratory resistive-loaded breathing tasks in five quadriplegic and five normal subjects. Each subject performed three breathing tasks that spanned a range of work rates (Wtot). Configurational changes of the abdomen and upper, lower, and transverse rib cage were assessed with magnetometers. We found that 1) in both groups, VO2resp increased linearly with Wtot over the range of tasks performed, 2) the mean slope of the regression line of VO2resp vs. Wtot was greater for quadriplegic than for normal subjects (3.7 +/- 0.8 vs. 2.0 +/- 0.7 ml O2/J, P less than 0.01), 3) efficiency of breathing (Wtot/VO2resp) was less for quadriplegic than for normal subjects (1.9 +/- 0.6 vs. 3.5 +/- 1.4%, P less than 0.001), 4) during inhalation, upper and lower rib cages behaved similarly in the two groups, but the quadriplegic subjects had a decrease in transverse rib cage and a much greater increase in abdomen than normal subjects, and 5) functional residual capacity decreased in normal but not in quadriplegic subjects during the breathing tasks. We conclude that the lesser efficiency of breathing in quadriplegia may be related to the elastic work of chest wall distortion, shorter mean operational diaphragm length, and possibly differences between normal and quadriplegic subjects in mechanical advantage of available inspiratory muscles.     

Effect of hypercapnia and PEEP on expiratory muscle EMG and shortening

The present study examined the effects of hypercapnia and positive end-expiratory pressure (PEEP) on the electromyographic (EMG) activity and tidal length changes of the expiratory muscles in 12 anesthetized, spontaneously breathing dogs. The integrated EMG activity of both abdominal (external oblique, internal oblique, rectus abdominis, and transverse abdominis) and thoracic (triangularis sterni, internal intercostal) expiratory muscles increased linearly with increasing PCO2 and PEEP. However, with both hypercapnia and PEEP, the percent increase in abdominal muscle electrical activity exceeded that of thoracic expiratory muscle activity. Both hypercapnia and PEEP increased the tidal shortening of the external oblique and rectus abdominis muscles. Changes in tidal length correlated closely with simultaneous increases in muscle electrical activity. However, during both hypercapnia and PEEP, length changes of the external oblique were significantly greater than those of the rectus abdominis. We conclude that both progressive hypercapnia and PEEP increase the electrical activity of all expiratory muscles and augment their tidal shortening but produce quantitatively different responses in the several expiratory muscles.     

Expiratory muscle fatigue in normal subjects

We examined expiratory muscle fatigue during expiratory resistive loading in 11 normal subjects. Subjects breathed against expiratory resistances at their own breathing frequency and tidal volume until exhaustion or for 60 min. Respiratory muscle strength was assessed from both the maximum static expiratory and inspiratory mouth pressures (PEmax and PImax). At the lowest resistance, PEmax and PImax measured after completion of the expiratory loaded breathing were not different from control values. With higher resistance, both PEmax and PImax were decreased (P less than 0.05), and the decrease lasted for greater than or equal to 60 min. The electromyogram high-to-low frequency power ratio for the rectus abdominis muscle decreased progressively during loading (P less than 0.01), but the integrated EMG activity did not change during recovery. Transdiaphragmatic pressure during loading was increased 3.6-fold compared with control (P less than 0.05). These findings suggest that expiratory resistive loaded breathing induces muscle fatigue in both expiratory and inspiratory muscles. Fatigue of the expiratory muscles can be attributed directly to the high work load and that of the inspiratory muscles may be related to increased work due to shortened inspiratory time.     

Steady-state response of quadriplegic subjects to inspiratory resistive load

Normal subjects preserve tidal volume (VT) in the face of added inspiratory resistance by increasing maximal amplitude and duration of the rising phase of respiratory driving pressure (DP) and by changing the shape of this phase to one that is more concave to the time axis. To explore the possible role of chest wall afferents in mediating these responses, we determined averaged DP in eight quadriplegic subjects during steady-state unloaded breathing and while breathing through an inspiratory resistance (8.5 cmH2O X 1(-1) X s). As with normal subjects, quadriplegics preserved VT (loaded VT = 106% control) by utilizing all three mechanisms. However, prolongation of the inspiratory duration derived from the DP waveform (+22% vs. +42%) and shape response were significantly less in the quadriplegic subjects. Shape response was completely absent in subjects with C4 lesions. The results provide strong evidence that respiratory muscle spindles are responsible for shape response and that changes in afferent feedback from the chest wall play an important role in mediating inspiratory prolongation.     

Effect of head-down tilt on respiratory responses and human inspiratory muscles activity

The effect of head-down tilt on respiration and diaphragmal and parasternal muscles activity was investigated in 11 healthy subjects. The short-time (30 min) head-down tilt posture (-30 degrees relatively horizont) increased the inspiratory time (P < 0.05), decreased breathing frequency (P < 0.05), inspiratory and expiratory flow rate (P < 0.05) and increased the airway resistance (P < 0.05) compared with values in vertical posture. There were no significant changes in tidal volume and minute ventilation. Constant values of tidal volume and minute ventilation during head-down tilt were provided by increasing in EMG activity of parasternal muscles more then twice. It was established that the contribution of chest wall inspiratory muscles increased while the diaphragm's contribution decreased during head-down spontaneous breathing. Maximal inspiratory effort (Muller's maneuver) during head-down tilt evoked the opposite EMG-activity pattern: the contribution of inspiratory thoracic muscles was decreased and diaphragm's EMG-activity was increased compared with vertical posture. These results suggest that coordinate modulations in inspiratory muscles activity allows to preserve the functional possibility of human inspiratory muscles during short-time head-down tilt.     

Influence of upper airway sensory receptors on respiratory muscle activation in humans

We reasoned that neural information from upper airway (UA) sensory receptors could influence the relationship between UA and diaphragmatic neuromuscular responses to hypercapnia. In this study, the electromyographic (EMG) activities of the alae nasi (AN), genioglossus (GG), and chest wall (CW) or diaphragm (Di) to ventilatory loading were assessed in six laryngectomized, tracheostomized human subjects and in six subjects breathing with an intact UA before and after topical UA anesthesia. The EMG activities of the UA and thoracic muscles increased at similar rates with increasing hypercapnia in normal subjects, in subjects whose upper airways were anesthetized, and in laryngectomized subjects breathing with a cervical tracheostomy. Furthermore, in the laryngectomized subjects, respiratory muscle EMG activation increased with resistive inspiratory loading (15 cmH2O X l-1 X s) applied at the level of a cervical tracheostomy. At an average expired CO2 fraction of 7.0%, resistive loading resulted in a 93 +/- 26.3% (SE) increase in peak AN EMG activity, a 39 +/- 2.0% increase in peak GG EMG activity, and a 43.2 +/- 16.5% increase in peak CW (Di) EMG activity compared with control values. We conclude that the ventilatory responses of the UA and thoracic muscles to ventilatory loading are not substantially influenced by laryngectomy or UA anesthesia.     

Improved compensatory postural adjustments of the deep abdominals following exercise in people with chronic low back pain

The purpose of this study was to determine if 8 weeks of exercise affects motor control in people with chronic low back pain (CLBP), measured by anticipatory (APAs) and compensatory postural adjustments (CPAs). APAs and CPAs were measured prior to and following 8 weeks in two groups of people with CLBP: an exercise group (n = 12) who attended three exercise sessions per week for 8 weeks; and a non-exercise control group (n = 12) who were advised to continue their usual activities for the duration of the study. APAs and CPAs were recorded during unilateral arm flexion, bilaterally from rectus abdominis (RA), transverse abdominis/internal oblique (TA/IO), and erector spinae (ES) via surface electromyography. Analysis of muscle onsets and APA amplitudes suggests APAs did not change for either group. Ipsi-lateral TA/IO CPAs increased for the exercise group and ipsi-lateral TA/IO CPAs decreased for the control group. Only exercise promoted a pattern of TA/IO activity during CPAs similar to healthy individuals, suggesting improved control of rotational torques. These results show motor control improvement following exercise in people with CLBP, highlighted by improved side specific control of TA/IO.