Vincent Cantin

Changes in the flexion relaxation response induced by lumbar muscle fatigue

BackgroundThe flexion relaxation phenomenon (FRP) is an interesting model to study the modulation of lumbar stability. Previous investigations have explored the effect of load, angular velocity and posture on this particular response. However, the influence of muscular fatigue on FRP parameters has not been thoroughly examined. The objective of the study is to identify the effect of erector spinae (ES) muscle fatigue and spine loading on myoelectric silence onset and cessation in healthy individuals during a flexion-extension task.MethodsTwenty healthy subjects participated in this study and performed blocks of 3 complete trunk flexions under 4 different experimental conditions: no fatigue/no load (1), no fatigue/load (2), fatigue/no load(3), and fatigue/load (4). Fatigue was induced according to the Sorenson protocol, and electromyographic (EMG) power spectral analysis confirmed that muscular fatigue was adequate in each subject. Trunk and pelvis angles and surface EMG of the ES L2 and L5 were recorded during a flexion-extension task. Trunk flexion angle corresponding to the onset and cessation of myoelectric silence was then compared across the different experimental conditions using 2 × 2 repeated-measures ANOVA.ResultsOnset of myoelectric silence during the flexion motion appeared earlier after the fatigue task. Additionally, the cessation of myoelectric silence was observed later during the extension after the fatigue task. Statistical analysis also yielded a main effect of load, indicating a persistence of ES myoelectric activity in flexion during the load condition.ConclusionThe results of this study suggest that the presence of fatigue of the ES muscles modifies the FRP. Superficial back muscle fatigue seems to induce a shift in load-sharing towards passive stabilizing structures. The loss of muscle contribution together with or without laxity in the viscoelastic tissues may have a substantial impact on post fatigue stability.

Changes in the flexion-relaxation response induced by hip extensor and erector spinae muscle fatigue

BackgroundThe flexion-relaxation phenomenon (FRP) is defined by reduced lumbar erector spinae (ES) muscle myoelectric activity during full trunk flexion. The objectives of this study were to quantify the effect of hip and back extensor muscle fatigue on FRP parameters and lumbopelvic kinematics.MethodsTwenty-seven healthy adults performed flexion-extension tasks under 4 different experimental conditions: no fatigue/no load, no fatigue/load, fatigue/no load, and fatigue/load. Total flexion angle corresponding to the onset and cessation of myoelectric silence, hip flexion angle, lumbar flexion angle and maximal trunk flexion angle were compared across different experimental conditions by 2 × 2 (Load × Fatigue) repeated-measures ANOVA.ResultsThe angle corresponding to the ES onset of myoelectric silence was reduced after the fatigue task, and loading the spine decreased the lumbar contribution to motion compared to the hip during both flexion and extension. A relative increment of lumbar spine motion compared to pelvic motion was also observed in fatigue conditions.ConclusionsPrevious results suggested that ES muscles, in a state of fatigue, are unable to provide sufficient segmental stabilization. The present findings indicate that, changes in lumbar-stabilizing mechanisms in the presence of muscle fatigue seem to be caused by modulation of lumbopelvic kinematics.

Load and speed effects on the cervical flexion relaxation phenomenon

BackgroundThe flexion relaxation phenomenon (FRP) represents a well-studied neuromuscular response that occurs in the lumbar and cervical spine. However, the cervical spine FRP has not been investigated extensively, and the speed of movement and loading effects remains to be characterized. The objectives of the present study were to evaluate the influence of load and speed on cervical FRP electromyographic (EMG) and kinematic parameters and to assess the measurement of cervical FRP kinematic and EMG parameter repeatability.MethodsEighteen healthy adults (6 women and 12 men), aged 20 to 39 years, participated in this study. They undertook 2 sessions in which they had to perform a standardized cervical flexion/extension movement in 3 phases: complete cervical flexion; the static period in complete cervical flexion; and extension with return to the initial position. Two different rhythm conditions and 3 different loading conditions were applied to assess load and speed effects. Kinematic and EMG data were collected, and dependent variables included angles corresponding to the onset and cessation of myoelectric silence as well as the root mean square (RMS) values of EMG signals. Repeatability was examined in the first session and between the 2 sessions.ResultsStatistical analyses revealed a significant load effect (P < 0.001). An augmented load led to increased FRP onset and cessation angles. No load × speed interaction effect was detected in the kinematics data. A significant load effect (P < 0.001) was observed on RMS values in all phases of movement, while a significant speed effect (P < 0.001) could be seen only during the extension phase. Load × speed interaction effect was noted in the extension phase, where higher loads and faster rhythm generated significantly greater muscle activation. Intra-session and inter-session repeatability was good for the EMG and kinematic parameters.ConclusionsThe load increase evoked augmented FRP onset and cessation angles as well as heightened muscle activation. Such increments may reflect the need to enhance spinal stability under loading conditions. The kinematic and EMG parameters showed promising repeatability. Further studies are needed to assess kinematic and EMG differences between healthy subjects and patients with neck pain.

Effects of two types of foot orthoses on lower limb muscle activity before and after a one-month period of wear

The purpose of this study was to quantify the effects of two types of foot orthoses (FOs) on muscle activity during walking. Twenty-one healthy participants were recruited to walk on a five-meter walkway with a control condition (no FOs) and two experimental conditions (FOs and FOs with lateral bar). The experimental protocol was performed before and after a one-month period of wear for each experimental condition. Electromyographic signals were recorded for six muscles (gluteus medius, vastus lateralis, medial gastrocnemius, lateral gastrocnemius, peroneus longus and tibialis anterior). Mean muscle activity was analyzed during the contact, the combined midstance/terminal stance and the pre-swing phases of gait. Peak amplitude and time to peak amplitude were quantified during the stance phase. Unacceptable level of variability was observed between the testing sessions. Therefore, no comparisons were performed to compare the effects of the experimental conditions between testing sessions. After a one-month period of wear, FOs with lateral bar decreased peak amplitude and mean activity of the peroneus longus muscle during the combined midstance/terminal stance phase and FOs decreased peak amplitude and mean activity of the tibialis anterior muscle during the contact phase compared to a control condition. In conclusion, repeated-test design should be used with caution when assessing the muscular adaptation to the wear of FOs for a certain period of time. More studies are needed to determine if the decreased activity of the peroneus longus muscle could be of benefit to treat pathologies such as peroneal tendinopathy or lateral ankle instability.

Effects of chronic ankle instability on kinetics, kinematics and muscle activity during walking and running: A systematic review

The aim of this study is to systematically review and appraise studies assessing the effects of chronic ankle instability (CAI) on kinetics, kinematics and muscle activity during walking and running. The primary search was conducted in PubMed, Embase, CINAHL, AMED and SPORTDiscus. Only studies that compared participants with CAI with healthy participants and assessed kinetics, kinematics or muscle activity during walking or running were included. The risk of bias assessment was conducted using a modified version of the Quality Index checklist. A total of 509 articles were retrieved. After the title and abstract review, 34 articles underwent full-text review and risk of bias assessment. Following a complementary search and assessment of full manuscripts, 24 articles fulfilled all inclusion criteria and methodological requirements, of which 8 articles investigated muscle activity, 14 kinematics and 7 kinetics. During walking, participants with CAI presented increased ankle and rearfoot inversion, ankle plantarflexion, lateral foot vertical forces and peroneus longus muscle activity. During running, kinematic differences were similar to those during walking, but few studies quantified kinetics and muscle activity to draw sound conclusions. This systematic review reports new information on the effects of CAI on gait parameters since the last published review, especially with regard to muscle activity, kinematic and kinetic parameters during running. Methodological quality of the studies assessing kinetics during walking was found to be poor. Future studies should use standardized selection criteria when assessing participants with CAI to increase the external validity of the results.

Physiological and Psychological Predictors of Short-Term Disability in Workers with a History of Low Back Pain: A Longitudinal Study

Despite an elusive pathophysiology, common characteristics are often observed in individuals with chronic low back pain (LBP). These include psychological symptoms, altered pain perception, altered pain modulation and altered muscle activation. These factors have been explored as possible determinants of disability, either separately or in cross-sectional studies, but were never assessed in a single longitudinal study. Therefore, the objective was to determine the relative contribution of psychological and neurophysiological factors to future disability in individuals with past LBP. The study included two experimental sessions (baseline and six months later) to assess cutaneous heat pain and pain tolerance thresholds, pain inhibition, as well as trunk muscle activation. Both sessions included the completion of validated questionnaires to determine clinical pain, disability, pain catastrophizing, fear-avoidance beliefs and pain vigilance. One hundred workers with a history of LBP and 19 healthy individuals took part in the first experimental session. The second experimental session was exclusively conducted on workers with a history of LBP (77/100). Correlation analyses between initial measures and disability at six months were conducted, and measures significantly associated with disability were used in multiple regression analyses. A first regression analysis showed that psychological symptoms contributed unique variance to future disability (R2 = 0.093, p = .009). To control for the fluctuating nature of LBP, a hierarchical regression was conducted while controlling for clinical pain at six months (R2 = 0.213, p < .001) where pain inhibition contributed unique variance in the second step of the regression (R2 change = 0.094, p = .005). These results indicate that pain inhibition processes may constitute potential targets for treatment to alleviate future disability in individuals with past or present LBP. Then again, the link between psychological symptoms and pain inhibition needs to be clarified as both of these factors are linked together and influence disability in their own way.

Is performance in goal oriented head movements altered in patients with tension type headache

BackgroundHead repositioning tasks have been used in different experimental and clinical contexts to quantitatively measure motor control performance. Effects of pain on sensorimotor control have often been described in various musculoskeletal conditions and may provide relevant information with regard to potential mechanisms underlying tension-type headaches. The purpose of the current study was to compare the performance of patients with tension-type headache and healthy participants in a cervical aiming task using the Fitts’ task paradigm.MethodsPatients with tension-type headache and healthy controls were compared in a cervical aiming task. Participants were asked to move their head as quickly, and precisely as possible to a target under various experimental conditions. Dependent variables included movement time, variable error, constant error and absolute error.ResultsAs predicted by Fitts’ law, decreasing target size and increasing head rotation amplitudes yielded longer movement times in both groups. Participants with tension-type headache, when compared to healthy participants showed a significant increase in both constant and absolute errors for each of the four conditions.ConclusionDecreased motor performance was observed in participants with tension-type headache, likely due to altered motor control of the neck musculature. Future research is warranted to investigate the clinical aspect related to decrease in motor performance.

Effects of Foot Orthoses Extrinsic Rearfoot and Forefoot Posts on Muscle Activity During Walking: A Case Study

Introduction In clinical practice, different types of rearfoot and forefoot extrinsic posts are regularly added to foot orthoses (FOs) to make the treatment more specific. However, to this day, their effects on muscle activity during walking are still unclear and few studies have quantified them. The purpose of this case study was to quantify the effects of FOs with different extrinsic rearfoot and forefoot posts on muscle activity during walking to generate hypotheses with the goal to develop a more complex experimental design for further studies. Materials and Methods A 26-year-old man with hyperpronated feet was recruited to walk on a 5-meter walkway with seven pairs of FOs with different extrinsic rearfoot and forefoot posts (no post, external oblique rearfoot post, internal oblique rearfoot post, straight rearfoot post, rearfoot and forefoot posts, rearfoot and forefoot posts at 2° varus, and rearfoot and forefoot posts at 5° varus). Mean activity of eight lower-limb muscles (gluteus medius, vastus lateralis, vastus medialis, biceps femoris, medial gastrocnemius, lateral gastrocnemius, fibularis longus, and tibialis anterior) was analyzed during the three phases of the walking cycle (contact, midstance, and propulsion). Peak root mean square (RMS) amplitude was also measured. Results Significant differences were observed between the control and the experimental conditions for mean muscle activity and peak RMS amplitude during the gait cycle. Results were variable between conditions. However, in general, more muscle activity was observed when increasing the frontal plane inclination of the extrinsic rearfoot and forefoot posts. Conclusions The addition of extrinsic rearfoot and forefoot posts to the FOs can modulate muscle function during walking. However, to this day, not enough data are available to build a clinical guideline, and it is still unknown if they can have positive effects on musculoskeletal pathologies of the lower limb.

Contribution of Load Expectations to Neuromechanical Adaptations During a Freestyle Lifting Task: A Pilot Study

Objectives The main goal of this study was to determine to what extent load expectations modulate neuromechanical adaptations in individuals with and without chronic low back pain (cLBP) when lifting and lowering various loads. The second goal was to assess the feasibility of a simple lifting protocol during which expectations about loads were manipulated. Methods Seventeen participants with cLBP and 18 participants without low back pain were asked to lift and lower boxes of mild to moderate loads. Two kinds of expectations (lighter and heavier) were respectively associated to each experimental block. Self‐reported exertion was assessed to control for expectations modulation. Erector spinae and vastus lateralis electromyography (EMG) activity were recorded and kinematics angle calculated. Results The results showed a main effect of expectations, with loads introduced as heavier being associated to a higher exertion compared with loads introduced as lighter. EMG activity analyses revealed significant interaction involving expectations, movement phase, and loads, as well as significant differences between groups. Kinematic angles did not reveal any significant effect of expectations nor group during the lifting phase. Conclusions Psychological factors may contribute to neuromechanical adaptations to low back pain. Our preliminary findings show that expectations about loads may result in neuromechanical differences between individuals with cLBP and those without cLBP. This pilot study showed that testing the manipulation of expectations and EMG records was feasible but highlighted the need to go beyond single infrared markers to assess kinematics.

O5 Differences in vertical ground reaction forces in individuals with chronic ankle instability during walking

Study Design Case-control study. Objectives To compare the vertical ground reaction forces (GRF) of individuals with and without chronic ankle instability (CAI), shod or barefoot, during normal and fast walking. Background CAI is a condition that often occurs after sustaining an ankle sprain. Kinetic differences between participants with and without CAI during walking were previously reported. However, some studies assessed these parameters with shoes while others had the participants walk barefoot. No study has yet investigated if there are differences in GRF when walking shod or barefoot in participants with and without CAI. Furthermore, no studies have quantified the effects of walking speed on these parameters. Methods and Measures Two groups of 21 participants (with and without CAI) were recruited. All participants performed five overground walking trials, shod and barefoot, at normal and fast walking speeds. During these tasks, the GRF were measured with a force platform embedded in the floor on the participants’ path. The variables analysed were the impact peak, the active peak, the average loading rate (AVL) and the time of impact and active peaks. GRF differences were compared with repeated-measures analysis of variance. The level of statistical significance was set at p<0.05 and Hedges’ g>0.5. Results No significant differences were observed between groups for all variables. However, significant condition and speed effects were found. Earlier and lower impact peak were observed when walking barefoot compared to shod. The analyses also yielded earlier and lower impact peak, a delayed active peak and a lower AVL in normal compared to fast walking. Conclusions These results suggest that participants with CAI do not have altered GRF during walking. It has been previously reported that participants with CAI have altered GRF during running. It would be interesting to assess if significant differences are only observed in more challenging tasks.