Triceps Surae Muscle Group Research Articles

Manual Therapy Versus Exercise Therapy in Patients with Osteoarthritis of Knee -A Comparative Study

AIM OF THE STUDY: The aim of the study to compare the effectiveness of manual therapy versus exercise therapy in patients with knee osteoarthritis in terms of decreasing pain HYPOTHESIS • Null Hypothesis: There may be no significant difference in the effectiveness of manual therapy and exercise therapy in patients with knee osteoarthritis • Alternate Hypothesis: There may be significant difference in the effectiveness of manual therapy and exercise therapy in patients with knee osteoarthritis INTERVENTION Group A: MANUAL THERAPY Manual physiotherapy protocol consisted of Treatment is done for two sessions per week for four weeks. Knee Mandatory interventions: 1. Knee flexion, non-thrust Antero-posterior directed force to the tibia, 2. Tibio-femoral joint ,non-thrust 3. Knee extension, non-thrust Postero-anterior directed force to the tibia 4. Tibio-femoral joint, non-thrust 5. Patellar gliding force, non-thrust 6. Manual stretch to quadriceps, hamstring, triceps surae muscle groups 7. Soft tissue manipulation ,quadriceps and Peripatellar connective tissue, hamstring, hip adductor and triceps surae muscles groups Treatment is done for two sessions per week for four weeks. Group B: EXERCISE THERAPY This group performed a closely supervised standardized knee exercise program at twice a week for four weeks at eight treatment sessions. This program consists of active range of motion exercise for knee, muscle strengthening exercise for hip and knee, muscle stretching for lower limbs and riding a stationary bike. Aerobic exercises • Up to 10 minutes stationary bicycle or walk. Stretching exercises: • Standing calf stretch – 3 repetitions with 30 sec hold • Supine hamstring stretch -3 repetitions with 30 sec hold • Prone quadriceps stretch –3 repetitions with 30 sec hold Range of motion exercises: • In long sitting position, • Knee mid flexion to end range extension – two 30 sec bouts with 3 sec hold at end range • In long sitting position, knee mid flexion to end range flexion – two sec bouts with 3 sec hold at end range Strengthening exercises: • Static quad sets in knee extension –one set of 10 repetitions with 6 sec hold,10 sec rest between repetitions. • Short arc terminal extension exercises for the knee joint. • Quadriceps non-weight bearing progressive resistance exercises with weighted cuffs. • Supine Straight Leg Rise (SLR) Neuro muscular control exercises: Closed chain progression: • Seated leg press – one 30 sec bout • Standing weight –shifting exercises • Side- stepping • Step ups • Forward-backward and shuttle – walking drills RESULTS: Knee function of all patients increased significantly after the 4-week intervention program in both the groups of MANUAL THERAPY and EXERCISE THERAPY but Group A Manual therapy improved more significantly when compared to Group B Exercise therapy. CONCLUSION: Treatment effect was more in the patients received Manual therapy when compared to Exercise therapy. This finding suggest that Manual therapy can be useful intervention supplement in patients with osteoarthritis of knee.

Estrogen, Exercise Training, and Nitric-oxide Mediated Sympatholysis

Our laboratory has previously reported that nitric oxide (NO)-mediated inhibition of sympathetic vasoconstriction in contracting muscle (sympatholysis) was enhanced in female, compared with male rats. Estrogen has been shown to modulate NO synthase (NOS) expression and NO-mediated sympatholysis. Therefore, this study investigated the hypothesis that NO-mediated inhibition of sympathetic vasoconstriction in resting and contracting skeletal muscle of female rats would be a function of estrogen bioavailability. Further, exercise training has been shown to enhance sympatholysis. Thus, we also investigated the hypothesis that exercise training would restore sympatholysis in estrogen-deficient rats. Female Sprague-Dawley rats were randomized to sedentary ovary-intact (SOI, n=10), sedentary ovariectomized (SOVX, n=9), exercise-trained (10 weeks, 5 days/week, 600m, 40m·min−1, 5% grade) ovary-intact (TOI, n=13), or exercise-trained ovariectomized (TOVX, n=10) groups. OVX rats had both ovaries surgically removed. Following sedentary behavior or exercise training, rats were anesthetized and instrumented for measurement of blood pressure, femoral vascular conductance (FVC), stimulation of the lumbar sympathetic chain, and contraction of the triceps surae muscle group. The percentage change of FVC (%FVC) in response to sympathetic chain stimulation delivered at 2 and 5 Hz was determined at rest and during muscle contraction (60% maximal contractile force) in control, selective neuronal NOS (nNOS) inhibition (SMTC; 0.6 mg·kg−1 IV), and non-selective NOS inhibition (L-NAME; 10 mg·kg−1 IV) conditions. In the Control condition, sympathetic vasoconstrictor responsiveness (%FVC) in resting and contracting skeletal muscle was not different between groups. Under resting conditions, sympathetic vasoconstrictor responsiveness was not different following selective nNOS inhibition (p>0.05), but was increased (p<0.05, main effect of drug) following non-selective NOS inhibition compared with control and selective nNOS inhibition conditions at both 2 Hz and 5 Hz. During muscle contraction, sympathetic vasoconstrictor responsiveness to 2 Hz sympathetic stimulation was unchanged (p>0.05) in the presence of selective nNOS inhibition, but was increased (p<0.05, main effect of drug) following non-selective NOS inhibition compared with control and selective nNOS inhibition conditions. At 5 Hz, sympathetic vasoconstrictor responsiveness was increased (p<0.05, main effect of drug) by selective nNOS inhibition, and increased further (p<0.05, main effect of drug) by non-selective NOS inhibition. The magnitude of sympatholysis at 2 Hz was not different (p>0.05) between groups or drug conditions. At 5 Hz, sympatholysis was blunted (p<0.05, main effect of drug) in the selective nNOS inhibition condition, and further reduced (p<0.05, main effect of drug condition) following non-selective NOS inhibition in all groups. Sympatholysis was not different (p>0.05) between sedentary and exercise trained groups. In conclusion: 1) sympathetic vasoconstrictor responsiveness in resting and contracting skeletal muscle was not dependent on estrogen bioavailability; 2) NO blunted vasoconstriction in all groups, however, NO-mediated sympatholysis was not altered by estrogen status, and; 3) exercise training did not alter sympathetic vasoconstrictor responsiveness or sympatholysis regardless of estrogen bioavailability. NSERC, Canada, Canadian Foundation for Innovation. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Quantifying the effects of achilles tendon lengthening surgery: An intraoperative approach.

Achilles tendon lengthening (ATL) is frequently used in the treatment of foot deformities. However, there is currently no objective method to determine the optimal muscle length during surgery. We developed an intraoperative approach to evaluate the passive and active forces of the triceps surae muscle group before and after ATL and aimed to test the following hypotheses: 1) the ankle passive range of motion (ROM) increases, 2) passive muscle forces decrease post-ATL, and 3) forces measured from patients with non-neurological and neurological conditions demonstrate different characteristics. Passive forces at various ankle joint positions were measured in ten patients (11.3 ± 3.0years old) pre- and post-ATL using a force transducer attached to the Achilles tendon. In six patients, active isometric forces were measured by stimulating the triceps surae supramaximally. Passive forces decreased by 94.3% (p < 0.0001), and ROM increased by 89.4% (p < 0.0001) post-ATL. The pre-ATL passive forces were 70.8% ± 15.1% lower in patients with idiopathic foot deformities than in patients with neurological conditions (p < 0.001). The peak active force of 209.8 ± 114.3N was achieved at an ankle angle of 38.3° ± 16.0°, where the passive force was 6.3 ± 6.7N. The inter-individual variability was substantial in both groups. In conclusion, the hypotheses posed were supported. The present findings suggest that muscle passive and active force production as well as the inter-individual variability should be considered when planning further treatment.

Sex-related differences and effects of short and long trail running races on resting muscle-tendon mechanical properties.

The purpose of the study was to assess sex-related differences in resting mechanical properties and adaptations of skeletal muscles and tendons in response to trail running races of different distances using multi-site shear wave elastography assessments of the lower limb, force capacity and blood analyses. Sex differences in resting mechanical properties of knee extensor and plantar flexor muscles and tendons were characterized by shear wave velocity (SWV) measurements in healthy males (N=42) and females (N=25) trained in long-distance running. Effects of running distance on muscle and tendon properties were assessed in short (<60 km, N=23) vs. long (>100 km, N=26) distance races. Changes in isometric maximal voluntary contraction torque, serum C-reactive protein and creatine kinase activity were also quantified after running races. Higher SWV of relaxed triceps surae muscle was detected in females as compared to males before running races (+4.8%, p=0.006), but the significant increases in triceps surae muscle group (+7.0%, p=0.001) and patellar tendon SWV (+15.4%, p=0.001) after short-distance races were independent of sex. A significant decrease in triceps surae muscle SWV was found after long-distance races in the whole experimental population (-3.1%, p=0.049). Post-races increase in C-reactive protein and creatine kinase activity were significantly correlated to the relative decreases in triceps surae and quadriceps femoris skeletal muscle SWV (ρ=-0.56, p=0.001 and ρ=-0.51, p=0.001, respectively). Resting mechanical properties of muscles and tendons are affected by sex, and adaptations to trail races are related to running distance. Exercise-induced changes in resting skeletal muscle mechanical properties are associated with enhanced indirect markers of inflammation and muscle damage.

Sex Influence on the Functional Recovery Pattern After a Graded Running Race: Original Analysis to Identify the Recovery Profiles.

This study investigated the sex influence on the acute and delayed fatigue effects of a 20 km graded running race. Eighteen recreational runners, 10 women and 8 men, completed the race. The testing protocol included five sessions: a week before the race (PRE), 35 ± 15 min after (POST), 2 h, 2 and 4 days (2D and 4D) later. Each session included uni- and bilateral maximal isometric voluntary contractions of the knee extensors (MVC), a squat jump (SJ), and a drop jump (DJ). Acute and delayed muscle soreness (DOMS) were evaluated for the quadriceps, hamstring and triceps surae muscle groups. The 2D and 4D sessions included also a horizontal force-velocity test (HF-V) performed under five resistive conditions. For each test, a set of key variables was computed to characterize the lower limb functional recovery. Mixed ANOVA analyses revealed significant (sex × time) interactions, with larger acute drops for men in MVCs and earlier recovery for women in the bilateral MVC (p < 0.001) and DJ (p < 0.05) tests. Only women reported DOMS for the hamstrings at 2D (p < 0.001) and showed small improvements in pure concentric SJ (p < 0.05) and HF-V (p < 0.01) tests at 4D. As expected, DOMS disappeared prior to the complete functional recovery. These results confirmed the combined influence of testing task and sex on the functional recovery pattern while supporting a lesser and faster recovery in women. The originality of this study lies in the complexity and sex-dependence of the functional recovery pattern revealed by a multiple factorial analysis which was used to identify the most discriminating tests and variables in the recovery pattern. The obtained clusters highlighted some recovery profiles associated with greater risks of injury when starting to run again. However, the lack of sex × time interaction for normalized values emphasizes the major influence of men’s initially higher functional values compared to women.

Spinal motor mapping by epidural stimulation of lumbosacral posterior roots in humans.

SummaryEpidural electrical stimulation of the spinal cord is an emergent strategy for the neurological recovery of lower-extremity motor function. Motoneuron pools are thought to be recruited by stimulation of posterior roots. Here, we linked electromyographic data of epidurally evoked lower-extremity responses of 34 individuals with upper motoneuron disorders to a population model of the spinal cord constructed using anatomical parameters of thousands of individuals. We identified a relationship between segmental stimulation sites and activated spinal cord segments, which made spinal motor mapping from epidural space possible despite the complex anatomical interface imposed by the posterior roots. Our statistical approach provided evidence for low-threshold sites of posterior roots and effects of monopolar and bipolar stimulation previously predicted by computer modeling and allowed us to test the impact of different upper motoneuron disorders on the evoked responses. Finally, we revealed a statistical association between intraoperative and postoperative mapping of the spinal cord.

Ad libidum exercise improves functional sympatholysis in rats with spontaneous hypertension via the nitric oxide signal pathway

Objective To explore the effect of exercise on functional sympatholysis in rats modeling spontaneous hypertension and the role of the nitric oxide signal pathway. Methods Thirty Wistar rats with spontaneous hypertension were randomly divided into a sedentary group and an exercise group, each of 15, while another fifteen healthy rats acted as controls. The exercise group performed eight weeks of voluntary wheel running exercise while the other two groups did not. The rats were instrumented to stimulate the lumbar sympathetic chain (at 1 Hz, 2.5 Hz or 5 Hz) to induce vasoconstriction and the triceps surae muscle group was forced to contract by stimulating the tibial nerve electrically. The change in the femoral artery vascular conductance (FAVC) in response to sympathetic stimulation was recorded at rest and during contraction. The functional sympatholysis was calculated as the percentage difference in FAVC (△%FAVC) in response to sympathetic stimulation during muscular contraction and at rest (△%FAVC=%FAVC during contraction-%FAVC at rest). After administration of the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME), changes in FAVC were repeatedly determined. Results The average △%FAVC of the sedentary group was significantly lower than that of the control group at all stimulation frequencies, while the average △%FAVC in the exercise group was significantly higher than in the sedentary group. There were no significant differences between the exercise and control groups. After the administration of L-NAME, significant decrease was observed in the average △%FAVCs of the control and exercise groups, but there was no significant change in the sedentary group. Conclusion Voluntary exercise may improve functional sympatholysis in rats with spontaneous hypertension through improving NO-dependent signalling. Key words: Exercise; Hypertension; Functional sympatholysis; Nitric oxide

Muscle morphology of the lower leg in ambulant children with spastic cerebral palsy.

In this study we aimed to determine the lower limb morphological characteristics of skeletal muscle of ambulant children with spastic cerebral palsy (CP) and typically developing (TD) children. Seventeen children with spastic diplegic CP (10 boys and 7 girls, 5-12 years of age, Gross Motor Function Classification System [GMFCS] level I or II) and 19 TD children (8 boys and 11 girls, 5-11 years of age) underwent lower limb T1-weighted MRI. Morphological characteristics of the triceps surae, including muscle volume, anatomical cross-sectional area, muscle length, and subcutaneous adipose tissue, were digitally quantified, and the proportional distribution calculated. Children with GMFCS II had significantly reduced muscle volume, cross-sectional area, and muscle length, and increased subcutaneous fat compared with TD children. Children classified as GMFCS II consistently exhibited the greatest deficits in all morphology variables. Morphological variables were significantly different between the groups. These alterations have the potential to influence the functional capabilities of the triceps surae muscle group. Muscle Nerve 58:818-823, 2018.

Botulinum Toxin Conditioning Enhances Motor Axon Regeneration in Mouse and Human Preclinical Models

Background. Peripheral axon regeneration is improved when the nerve lesion under consideration has recently been preceded by another nerve injury. This is known as the conditioning lesion effect (CLE). While the CLE is one of the most robust and well characterized means to enhance motor axon regeneration in experimental models, it is not considered a clinically feasible strategy. A pharmacological means to re-produce the CLE is highly desirable. Objective. To test whether chemodenervation with a clinical grade formulation of botulinum toxin A (BoTX) would be sufficient to reproduce the CLE. Methods. We examined the effects of a 1-week preconditioning administration of BoTX on motor axon regrowth in both a mouse tibial nerve injury and human embryonic stem cell (hESC)–based model. We assessed neuronal reinnervation in vivo (mice) with retrograde tracers and histological analysis of peripheral nerve tissue after injections into the triceps surae muscle group. We assessed motor neuron neurite outgrowth in vitro (hESC) after incubation in BoTX by immunohistochemistry and morphometric analysis. Results. We found that BoTX conditioning treatment significantly enhanced outgrowth of both murine motor axons in vivo and human MN neurites in vitro. Conclusions. BoTX preconditioning represents a pharmacological candidate approach to enhance motor axon regeneration in specific clinical scenarios such as nerve transfer surgery. Further studies are needed to elucidate the molecular mechanism.

Real-Time Closed-Loop Functional Electrical Stimulation Control of Muscle Activation with Evoked Electromyography Feedback for Spinal Cord Injured Patients.

Functional electrical stimulation (FES) is a neuroprosthetic technique to help restore motor function of spinal cord-injured (SCI) patients. Through delivery of electrical pulses to muscles of motor-impaired subjects, FES is able to artificially induce their muscle contractions. Evoked electromyography (eEMG) is used to record such FES-induced electrical muscle activity and presents a form of [Formula: see text]-wave. In order to monitor electrical muscle activity under stimulation and ensure safe stimulation configurations, closed-loop FES control with eEMG feedback is needed to be developed for SCI patients who lose their voluntary muscle contraction ability. This work proposes a closed-loop FES system for real-time control of muscle activation on the triceps surae and tibialis muscle groups through online modulating pulse width (PW) of electrical stimulus. Subject-specific time-variant muscle responses under FES are explicitly reflected by muscle excitation model, which is described by Hammerstein system with its input and output being, respectively, PW and eEMG. Model predictive control is adopted to compute the PW based on muscle excitation model which can online update its parameters. Four muscle activation patterns are provided as desired control references to validate the proposed closed-loop FES control paradigm. Real-time experimental results on three able-bodied subjects and five SCI patients in clinical environment show promising performances of tracking the aforementioned reference muscle activation patterns based on the proposed closed-loop FES control scheme.

The Effect Of Varying Self-myofascial Release Duration On Subsequent Athletic Performance

Self-myofascial release (SMR) treatments appear to enhance joint range of motion (RoM) and restore movement function but the effects of different SMR durations on athletic performance have yet to be examined. PURPOSE: To investigate the effects of different SMR treatment durations (1 minute and 5 minutes) on joint RoM, power, and agility. METHODS: Twenty-four volunteers participated with ankle and knee joint RoM assessed using modified weight-bearing (WBL) and kneeling lunge (KL) tests. Vertical jump (VJ) performance and pro-agility (PA) sprint performance were also examined. All tests were conducted before and immediately after one-minute (SMR_1) and five-minutes (SMR_5) of SMR and immediately following a control (CONTR) condition. SMR was done on the quadriceps and triceps surae muscle groups using a standardized protocol and foam roller. Differences in dependent variables (VJ height, PA run time, WBL distance, KL angle) between treatment groups (SMR_1, SMR_5, CONTR) at two time-points (pre- and post-treatment) were analyzed using a 3 x 2-way repeated measures analysis of variance (ANOVA). Alpha = 0.05. Effect sizes (ES) were calculated to clarify the magnitude of the effect of differences between means from pre- to post-treatment for each treatment condition. RESULTS: KL angle increased following SMR_5 (16.4 %; ES = 0.85) when compared with SMR_1 (12.5 %; ES = 0.58). WBL distance showed little change following SMR treatments and the CONTR condition exhibited little effect on RoM tests. VJ height decreased following SMR_5 (5.1 %; ES = 0.26) but changed little following SMR_1 (0.7 %; ES = 0.03) and CONTR (1.9 %; ES = 0.10) conditions. PA run time improved slightly following SMR_1 (1.1 %) but deteriorated following CONTR (1.2 %) and SMR_5 (0.5 %). Effect size calculations for changes in PA, however, were trivial across all conditions (0.06 – 0.15). CONCLUSION: Extended periods of SMR may be recommended should improvements in joint RoM be required. If power output is a critical requirement of subsequent tasks, prolonged SMR treatment (i.e., 5-min) should be avoided.

The Effect of Exercise Training on Sympathetic Vasoconstrictor Responsiveness and Sympatholysis in Female Rats

Our laboratory has previously reported that aerobic exercise training enhances contraction‐mediated inhibition of sympathetic vasoconstriction (sympatholysis) in male rats. Whether aerobic exercise training has a similar effect in female rats has not been established. Therefore, the purpose of the present study was to investigate the hypothesis that aerobic exercise training would blunt sympathetic vasoconstrictor responsiveness and enhance sympatholysis in female rats. Female Sprague‐Dawley rats were randomly assigned to sedentary (n=10) or treadmill exercise training (n=8) groups (15 min at 40 m/min, 5% gradient; 5 d/week) for 10 weeks. Following the completion of the sedentary behavior or exercise training intervention, rats were anaesthetized and instrumented for stimulation of the lumbar sympathetic chain and the measurement of arterial blood pressure and femoral vascular conductance (FVC). The triceps surae muscle group was stimulated to contract rhythmically at 60% of maximal contractile force. The percentage change of FVC (Δ%FVC) in response to sympathetic stimulation delivered at 2 and 5 Hz was determined at rest and during contraction. At rest, sympathetic vasoconstrictor responsiveness (Δ%FVC) was not different (p&gt;0.05) between sedentary and exercise trained rats in response to sympathetic stimulation delivered at 2Hz (Sedentary: −39 ± 12 %; Exercise Trained: −45 ± 9 %) and 5Hz (Sedentary: −57 ± 8 %; Exercise Trained: −61 ± 9 %). Muscle contraction blunted (p&lt;0.05) sympathetic vasoconstrictor responsiveness in both sedentary and exercise trained rats and the magnitude of sympatholysis was not different (p&gt;0.05) between sedentary (2Hz: 24 ± 8 %; 5Hz: 29 ± 10 %) and exercise‐trained (2Hz: 30 ± 10 %; 5Hz: 29 ± 13 %) rats. These data demonstrate that aerobic exercise training does not alter sympathetic vasoconstrictor responsiveness or contraction mediated inhibition of sympathetic vasoconstriction (sympatholysis) in female rats. Further investigation is required to determine why female rats respond differently to exercise training than male rats.Support or Funding InformationNatural Sciences and Engineering Research Council of Canada, Canadian Foundation for Innovation, and Alberta Advanced Education and Technology.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

The Effect of Beta‐Adrenergic Receptor Blockade on Sympathetic Vasoconstrictor Responsiveness in Sedentary and Exercise‐Trained Female Rats

Stimulation of the sympathetic nervous system evokes the release of neurotransmitters and produces vasoconstriction that is primarily mediated by the binding of norepinephrine (NE) to alpha‐adrenergic receptors. However, NE may also bind to beta‐ adrenergic receptors and produce vasodilation that opposes vasoconstriction. Therefore, in the present study, we tested the hypothesis that beta‐adrenergic receptor blockade would augment sympathetic vasoconstrictor responsiveness in resting and contracting skeletal muscle of sedentary and exercise trained female rats, demonstrating beta‐adrenergic receptor mediated opposition of vasoconstriction. We also hypothesized that the increase in sympathetic vasoconstrictor responsiveness in the presence of beta‐adrenergic blockade would be larger in exercise‐trained rats, indicating that exercise training augments beta‐adrenergic receptor mediated opposition of vasoconstriction. Female Sprague‐Dawley rats were randomized to Sedentary (n=8, 265 ± 28 g) and Exercise Trained (n=9, 290 ± 27 g) groups. Exercise Trained rats completed a 4‐week treadmill training regimen (5 d/week, 15 min at 40 m/min, 5% gradient). Subsequently, rats were anaesthetized and instrumented for the measurement of femoral vascular conductance (FVC), stimulation of the lumbar sympathetic chain, and contraction of the triceps surae muscle group. The percentage change of femoral vascular conductance (Δ%FVC) in response to sympathetic chain stimulation delivered at 2 and 5 Hz was determined at rest and during triceps surae muscle contraction (60% maximal contractile force) before (Control) and after beta‐adrenergic blockade (Propranolol; 0.075 mg/kg body mass, I.V.). Sympathetic vasoconstrictor responsiveness (Δ%FVC) was not different (P &gt; 0.05) between Sedentary and Exercise Trained rats at rest or during contraction. At rest, beta‐adrenergic receptor blockade did not increase (P &gt; 0.05) sympathetic vasoconstrictor responsiveness in Sedentary (Control: 2Hz: −34 ± 9 %, 5Hz: −53 ± 8 %; Propranolol: 2Hz: −31 ± 10 %, 5Hz: −49 ± 8 %) or Exercise Trained (Control: 2Hz: −38 ± 9 %, 5Hz: −57 ± 8 %; Propranolol: 2Hz: −34 ± 7 %, 5Hz: −53 ± 8 %) rats. Similarly, beta‐adrenergic receptor blockade did not increase (P &gt; 0.05) sympathetic vasoconstrictor responsiveness during exercise in Sedentary (Control: 2Hz: −7 ± 4 %, 5Hz: −20 ± 11 %; Propranolol: 2Hz: −6 ± 5 %, 5Hz: −18 ± 10 %) or Exercise Trained (Control: 2Hz: −10 ± 8 %, 5Hz: −28 ± 8 %; Propranolol: 2Hz: −6 ± 5 %, 5Hz: −24 ± 12 %) rats. In conclusion, beta‐adrenergic receptor blockade did not augment sympathetic vasoconstrictor responsiveness in resting or contracting skeletal muscle of sedentary or exercise‐trained female rats, suggesting that beta‐adrenergic receptor mediated vasodilation did not oppose vasoconstriction, regardless of training status.Support or Funding InformationNatural Sciences and Engineering Research Council of Canada, Canadian Foundation for Innovation, and Alberta Advanced Education and Technology.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Common neural structures activated by epidural and transcutaneous lumbar spinal cord stimulation: Elicitation of posterior root-muscle reflexes.

Epidural electrical stimulation of the lumbar spinal cord is currently regaining momentum as a neuromodulation intervention in spinal cord injury (SCI) to modify dysregulated sensorimotor functions and augment residual motor capacity. There is ample evidence that it engages spinal circuits through the electrical stimulation of large-to-medium diameter afferent fibers within lumbar and upper sacral posterior roots. Recent pilot studies suggested that the surface electrode-based method of transcutaneous spinal cord stimulation (SCS) may produce similar neuromodulatory effects as caused by epidural SCS. Neurophysiological and computer modeling studies proposed that this noninvasive technique stimulates posterior-root fibers as well, likely activating similar input structures to the spinal cord as epidural stimulation. Here, we add a yet missing piece of evidence substantiating this assumption. We conducted in-depth analyses and direct comparisons of the electromyographic (EMG) characteristics of short-latency responses in multiple leg muscles to both stimulation techniques derived from ten individuals with SCI each. Post-activation depression of responses evoked by paired pulses applied either epidurally or transcutaneously confirmed the reflex nature of the responses. The muscle responses to both techniques had the same latencies, EMG peak-to-peak amplitudes, and waveforms, except for smaller responses with shorter onset latencies in the triceps surae muscle group and shorter offsets of the responses in the biceps femoris muscle during epidural stimulation. Responses obtained in three subjects tested with both methods at different time points had near-identical waveforms per muscle group as well as same onset latencies. The present results strongly corroborate the activation of common neural input structures to the lumbar spinal cord—predominantly primary afferent fibers within multiple posterior roots—by both techniques and add to unraveling the basic mechanisms underlying electrical SCS.

A comparison of H-reflex in the triceps surae muscle group in patients with S1 radiculopathy

Despite differences in the anatomical and physiological characteristics of the medial gastrocnemius (MG), lateral gastrocnemius (LG), and soleus (Sol) muscles, it is common practice to investigate them as single triceps surae H-reflex recordings. The aim of this study was to compare the latencies of H-reflex recordings from the Sol, MG, and LG in patients with explicit magnetic resonance imaging (MRI) evidence of unilateral S1 radiculopathy and also compare their diagnostic yield in varied clinical characteristics (i.e., symptom duration and severity of involvement). We found a significant difference between H-reflex latencies of Sol and the two others (p < 0.05 for both comparisons). Although Sol had more sensitivity in patients with positive straight leg raising (SLR) of 30°–50° and also the sub-acute phase of the disease, and MG and LG had more sensitivity in the acute phase of the disease and patients with positive SLR of 50°–70°, there were no statistically significant differences between diagnostic ability of the three heads of the triceps surae in various clinical settings and they can be used interchangeably in patients with suspected S1 radiculopathies.

Effects of bed rest and the use of intermittent centrifugation to protect human balance and neuromotor reflexes

Intermittent artificial gravity (AG) treatments may reduce bone, muscle, and cardiovascular deconditioning during prolonged space flight; however, the effects of repeated centrifugation on central processing of vestibular information remain unknown. This study investigated the effects of one intermittent AG prescription on balance control and neuromotor reflex function in a ground-based study of subjects exposed to bed rest. Fifteen male volunteers were exposed to 21 days of 6° head-down-tilt (HDT) bed rest (BR) to simulate some of the effects of space flight. Eight were treated with daily 1 h AG exposures aboard a short radius centrifuge that provided 1-g footward loading at heart level. The other seven served as control subjects. Balance control was assessed using a computerized dynamic posturography (CDP) protocol modified by adding low frequency pitch-plane head movements. Neuromotor reflex function was assessed using tendon (MSR) and functional stretch reflex (FSR) data collected from the triceps surae muscle group. CDP performance was degraded by BR in both groups, but was unaffected by AG. BR also degraded MSR and FSR functions in both groups, but AG blunted the decrement in MSR. This AG prescription had little functionally relevant effect on balance control, but may have had some salutary effect on neuromotor reflexes.

Evidence of adaptations of locomotor neural drive in response to enhanced intermuscular connectivity between the triceps surae muscles of the rat.

The aims of this study were to investigate changes 1) in the coordination of activation of the triceps surae muscle group, and 2) in muscle belly length of soleus (SO) and lateral gastrocnemius (LG) during locomotion (trotting) in response to increased stiffness of intermuscular connective tissues in the rat. We measured muscle activation and muscle belly lengths, as well as hindlimb kinematics, before and after an artificial enhancement of the connectivity between SO and LG muscles obtained by implanting a tissue-integrating surgical mesh at the muscles' interface. We found that SO muscle activation decreased to 62%, while activation of LG and medial gastrocnemius muscles increased to 134 and 125%, respectively, compared with the levels measured preintervention. Although secondary additional or amplified activation bursts were observed with enhanced connectivity, the primary pattern of activation over the stride and the burst duration were not affected by the intervention. Similar muscle length changes after manipulation were observed, suggesting that length feedback from spindle receptors within SO and LG was not affected by the connectivity enhancement. We conclude that peripheral mechanical constraints given by morphological (re)organization of connective tissues linking synergists are taken into account by the central nervous system. The observed shift in activity toward the gastrocnemius muscles after the intervention suggests that these larger muscles are preferentially recruited when the soleus has a similar mechanical disadvantage in that it produces an unwanted flexion moment around the knee.NEW & NOTEWORTHY Connective tissue linkages between muscle-tendon units may act as an additional mechanical constraint on the musculoskeletal system, thereby reducing the spectrum of solutions for performing a motor task. We found that intermuscular coordination changes following intermuscular connectivity enhancement. Besides showing that the extent of such connectivity is taken into account by the central nervous system, our results suggest that recruitment of triceps surae muscles is governed by the moments produced at the ankle-knee joints.

Pyruvate Dehydrogenase Activity in Red and Superficial White Gastrocnemius Muscles of the Rat during Contraction

The increase in glucose oxidation during exercise is dependent upon the mitochondrial enzyme pyruvate dehydrogenase (PDH) which is allosterically regulated by reversible phosphorylation through a family of PDH kinases and phosphatases. However, the relationship between PDH activation and muscle fiber type during exercise has not been well described because fiber specific muscles have not been reported, and, because voluntary exercise involves motor unit recruitment which further complicates interpretation. To determine whether PDH activation differs in red versus superficial white muscle in vivo, gastrocnemius muscle contractile activity was controlled by electrical pacing via surgically implanted electrodes on the sciatic nerve of anesthetized male Wistar rats. Muscle force production of the triceps surae muscle group was recorded from the Achilles tendon and the knee pinned in place with a tungsten rod through the head of the femur. Gastrocnemius muscle samples were collected from the superficial white (predominantly Type IIb fibers) and deep red (predominantly Type IIb fibers) portions and freeze clamped at rest and during 5 min of twitch stimulation at 0.5Hz and 1.0Hz intensities. PDH activity was assayed in vitro using a radioisotopic tracer assay with [2‐14C]‐pyruvate as the substrate. Total PDH activity in the deep red gastrocnemius was almost two‐fold greater than that of the superficial white (1.9±0.1 vs 1.1±0.1 U/gWW, n=15). Fractional PDH activity (% total activity) was significantly increased in muscle samples collected from superficial white relative to deep red gastrocnemius at rest (15.0±2.0 vs 9.5±0.7%), and during 0.5Hz (60.9±8.1 vs 37.4±3.9%), and 1.0Hz stimulation frequencies (68.3±2.8 vs 40.5±2.8%) (n=4–5 for all groups). However, the active fraction of PDH activity was not different when comparing superficial white to deep red gastrocnemius at rest (0.12±0.02 vs 0.15±0.02 U/gWW) or during stimulation at 0.5Hz (0.67±0.08 vs 0.71±0.04 U/gWW), or 1.0Hz intensities (3±0.08 vs 0.82±0.02 U/gWW). These data suggest that the active fraction of PDH is dependent on the contraction intensity and therefore muscle fiber type differences do not appear to play a role in the number of PDH active sites during contractile activity. Therefore future designs of therapeutic exercise to optimize glucose disposal should be chosen based on the maximal intensity that can be maintained without fatigue to maximize the working muscle mass and PDH activity.Support or Funding InformationSupported by NIH DK095210

The influence of sodium bicarbonate on maximal force and rates of force development in the triceps surae and brachii during fatiguing exercise.

What is the central question of this study? Does metabolic alkalosis in humans, induced by sodium bicarbonate, affect rates of skeletal muscle fatigue differentially in muscle groups composed predominately of slow- and fast-twitch fibres? What is the main finding and its importance? Sodium bicarbonate exhibited no effect on the fatigue profile observed between triceps surae and brachii muscle groups during and after 2min of tetanic stimulation. For the first time in exercising humans, we have profiled the effect of sodium bicarbonate on the voluntary and involuntary contractile characteristics of muscle groups representative of predominately slow- and fast-twitch fibres. The effect of metabolic alkalosis on fibre-specific maximal force production and rates of force development (RFD) has been investigated previously in animal models, with evidence suggesting an improved capacity to develop force rapidly in fast- compared with slow-twitch muscle. We have attempted to model in vivo the fatigue profile of voluntary and involuntary maximal force and RFD in the triceps surae and brachii after sodium bicarbonate (NaHCO3 ) ingestion. In a double-blind, three-way repeated-measures design, participants (n=10) ingested either 0.3gkg-1 NaHCO3 (ALK) or equivalent calcium carbonate (PLA) prior to 2min of continuous (1Hz) supramaximal stimulation (300ms at 40Hz) of the triceps surae or brachii, with maximal voluntary efforts (maximal voluntary torque) coupled with direct muscle stimulation also measured at baseline, 1 and 2min. Metabolic alkalosis was achieved in both ALK trials but was not different between muscle groups. Regardless of the conditions, involuntary torque declined nearly 60% in the triceps brachii (P<0.001) and ∼30% in the triceps surae (P<0.001). In all trials, there was a significant decline in normalized involuntary RFD (P<0.05). Maximal voluntary torque declined nearly 28% but was not different between conditions (P<0.01), and although declining nearly 21% in voluntary RFD (P<0.05) there was no difference between PLA and ALK in either muscle group (P=0.93). Sodium bicarbonate exhibited no effect on the fatigue observed between representative fibre-type muscle groups on maximal voluntary and involuntary torque or rates of torque development during and after 2min of tetanic stimulation.

Multi-Electrode Array for Transcutaneous Lumbar Posterior Root Stimulation.

Interest in transcutaneous electrical stimulation of the lumbosacral spinal cord is increasing in human electrophysiological and clinical studies. The stimulation effects on lower limb muscles depend on the depolarization of segmentally organized posterior root afferents and, thus, the rostro-caudal stimulation site. In previous studies, selective stimulation was achieved by varying the positions of single self-adhesive electrodes over the thoracolumbar spine. Here, we developed a multi-electrode surface array consisting of 3 × 8 electrode pads and tested its stimulation-site specificity. The array was placed longitudinally over the spine covering the T10-L2 vertebrae. Two different hydrogel layer configurations were utilized: a single layer adhered to all electrode pads of the array and a configuration comprised of eight separate strips attached to the three transverse electrode pads of each level. Voltage measurements demonstrated that an effectively focused field distribution along the longitudinal extent of the array was not accomplished when using the single continuous hydrogel layer, and segmental selective stimulation of the posterior root afferents was not possible. The separate strips produced a focused electric field distribution at the rostro-caudal level of the electrode pads selected for stimulation. This configuration allowed for the preferential elicitation of posterior root-muscle reflexes in either the L2-L4 innervated quadriceps or the L5-S2 innervated triceps surae muscle groups. Such multi-electrode array for transcutaneous spinal cord stimulation shall allow for improved control of stimulation conditions in electrophysiological studies and time-dependent and site-specific stimulation patterns for neuromodulation applications.