Femoral and obturator neuropathies.

The femoral and obturator nerves both arise from the L2, L3, and L4 spinal nerve roots and descend into the pelvis before emerging in the lower limbs. The femoral nerve's primary function is knee extension and hip flexion, along with some sensory innervation to the leg. The obturator nerve's primary function is thigh adduction and sensory innervation to a small area of the medial thigh. Each may be injured by a variety of potential causes, many of them iatrogenic. Here, we review the anatomy of the femoral and obturator nerves and the clinical features and potential etiologies of femoral and obturator neuropathies. Their necessary investigations, including electrodiagnostic studies and imaging, their prognosis, and potential treatments, are discussed in this chapter.

Reciprocal inhibition of the thigh muscles in humans: A study using transcutaneous spinal cord stimulation.

Evaluating reciprocal inhibition of the thigh muscles is important to investigate the neural circuits of locomotor behaviors. However, measurements of reciprocal inhibition of thigh muscles using spinal reflex, such as H-reflex, have never been systematically established owing to methodological limitations. The present study aimed to clarify the existence of reciprocal inhibition in the thigh muscles using transcutaneous spinal cord stimulation (tSCS). Twenty able-bodied male individuals were enrolled. We evoked spinal reflex from the biceps femoris muscle (BF) by tSCS on the lumber posterior root. We examined whether the tSCS-evoked BF reflex was reciprocally inhibited by the following conditionings: (1) single-pulse electrical stimulation on the femoral nerve innervating the rectus femoris muscle (RF) at various inter-stimulus intervals in the resting condition; (2) voluntary contraction of the RF; and (3) vibration stimulus on the RF. The BF reflex was significantly inhibited when the conditioning electrical stimulation was delivered at 10 and 20 ms prior to tSCS, during voluntary contraction of the RF, and during vibration on the RF. These data suggested a piece of evidence of the existence of reciprocal inhibition from the RF to the BF muscle in humans and highlighted the utility of methods for evaluating reciprocal inhibition of the thigh muscles using tSCS.

Post-activation potentiation after isometric contractions is strongly related to contraction intensity despite the similar torque-time integral.

Post-activation potentiation (PAP) is defined as an enhanced contractile response of a muscle following its own contractile activity and is influenced by the intensity and duration of the conditioning contraction. The aim of this study was to determine if the combination of intensity and duration, that is, torque-time integral (TTI) is a determinant of PAP amplitude. We compared PAP amplitude following low-to-maximal voluntary conditioning contraction intensities with and without similar TTI in the knee extensors. Twelve healthy males completed two experimental sessions. Femoral nerve stimulation was applied to evoke single twitches on the relaxed quadriceps before and after isometric conditioning contractions of knee extensors. In one session, participants performed conditioning contractions without similar TTI (6 s at 100, 80, 60, 40 and 20% maximal voluntary contraction (MVC)), while they performed conditioning contractions with similar TTI in the other session (6 s at 100%, 7.5 s at 80%, 10 s at 60%, 15 s at 40%, and 30 s at 20% MVC). In both sessions, PAP amplitude was related to conditioning contraction intensity. The higher the conditioning contraction intensity with or without similar TTI, the higher PAP. Significant correlations were found (i) between PAP and conditioning contraction intensity with (r2 = 0.70; P < 0.001) or without similar TTI (r2 = 0.64; P < 0.001), and (ii) between PAP with and without similar TTI (r2 = 0.82; P < 0.001). The results provide evidence that TTI has a minor influence on PAP in the knee extensors. This suggests that to optimize the effect of PAP, it is more relevant to control the intensity of the contraction rather than the TTI.

Analgesic efficacy of local infiltration anaesthesia versus femoral nerve block in alleviating postoperative wound pain following total knee arthroplasty: A systematic review and meta-analysis.

Total knee arthroplasty (TKA) often involves significant postoperative pain, necessitating effective analgesia. This meta-analysis compares the analgesic efficacy of local infiltration anaesthesia (LIA) and femoral nerve block (FNB) in managing postoperative wound pain following TKA. Adhering to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, this meta-analysis was structured around the PICO framework, assessing studies that directly compared LIA and FNB in TKA patients. A comprehensive search across PubMed, Embase, Web of Science and the Cochrane Library was conducted without time restrictions. Studies were included based on specific criteria such as participant demographics, study design and outcomes like pain scores and opioid consumption. Quality assessment utilized the Cochrane Collaboration's risk of bias tool. The statistical approach was determined based on heterogeneity, with the choice of fixed- or random-effects models guided by the I2 statistic. Sensitivity analysis and evaluation of publication bias using funnel plots and Egger's linear regression test were also conducted. From an initial pool of 1275 articles, eight studies met the inclusion criteria. These studies conducted in various countries from 2007 to 2016. The meta-analysis showed no significant difference in resting and movement-related Visual Analogue Scale scores post-TKA between the LIA and FNB groups. However, LIA was associated with significantly lower opioid consumption. The quality assessment revealed a low risk of bias in most studies, and the sensitivity analysis confirmed the stability of these findings. There was no significant publication bias detected. Both LIA and FNB are effective in controlling postoperative pain in TKA patients, but LIA offers the advantage of lower opioid consumption. Its simplicity, cost-effectiveness and opioid-sparing nature make LIA the recommended choice for postoperative analgesia in knee replacement surgeries.

Differential effect of heteronymous feedback from femoral nerve and quadriceps muscle stimulation onto soleus H-reflex.

Excitatory feedback from muscle spindles, and inhibitory feedback from Golgi tendon organs and recurrent inhibitory circuits are widely distributed within the spinal cord to modulate activity between human lower limb muscles. Heteronymous feedback is most commonly studied in humans by stimulating peripheral nerves, but the unique effect of non-spindle heteronymous feedback is difficult to determine due to the lower threshold of excitatory spindle axons. A few studies suggest stimulation of the muscle belly preferentially elicits non-spindle heteronymous feedback. However, there remains a lack of consensus on the differential effect of nerve and muscle stimulation onto the H-reflex, and the relation of the heteronymous effects onto H-reflex compared to that onto ongoing EMG has not been determined. In this cross-sectional study, we compared excitatory and inhibitory effects from femoral nerve and quadriceps muscle belly stimulation onto soleus H-reflex size in 15 able-bodied participants and in a subset also compared heteronymous effects onto ongoing soleus EMG at 10% and 20% max. Femoral nerve stimulation elicited greater excitation of the H-reflex compared to quadriceps stimulation. The differential effect was also observed onto ongoing soleus EMG at 20% max but not 10%. Femoral nerve and quadriceps stimulation elicited similar inhibition of the soleus H-reflexes, and these results were better associated with soleus EMG at 20%. The results support surface quadriceps muscles stimulation as a method to preferentially study heteronymous inhibition at least in healthy adults. The primary benefit of using muscle stimulation is expected to be in persons with abnormal, prolonged heteronymous excitation. These data further suggest heteronymous feedback should be evaluated with H-reflex or onto ongoing EMG of at least 20% max to identify group differences or modulation of heteronymous feedback in response to treatment or task.

Single-injection nerve blocks for total knee arthroplasty: femoral nerve block versus femoral triangle block versus adductor canal block-a randomized controlled double-blinded trial.

INTRODUCTION: Femoral nerve block (FNB) is a well-established analgesic technique for TKA. However, it associates quadriceps weakness. Therefore, femoral triangle block (FTB) and adductor canal block (ACB) were proposed as effective alternative motor-spearing techniques. The primary objective was to compare quadriceps muscle strength preservation between FNB, FTB and ACB in TKA. The secondary objective was to analyze pain control and functional outcomes. METHODS: This is a prospective, double-blinded RCT. From April 2018 to April 2019, patients who undergo a primary TKA were randomized into three experimental groups: FNB-G1/FTB-G2/ACB-G3. Quadriceps strength preservation was measured as the difference in maximum voluntary isometric contraction (MVIC) preoperatively and postoperatively. RESULTS: Seventy-eight patients (G1, n = 22; G2, n = 26; G3, n = 30) met our inclusion/exclusion criteria. Patients with FNB retained significantly lower baseline MVIC at 6 h postoperatively (p = 0.001), but there were no differences at 24 and 48 h. There were no differences between the groups in functional outcomes at any time point. Patients in the FNB-G1 presented significant lower pain scores at 6 h (p = 0.01), 24 h (p = 0.005) and 48 h (p = 0.01). The highest cumulative opioid requirement was reported in ACB-G3. CONCLUSION: For patients undergoing TKA, FTB and ACB preserve quadriceps strength better than FNB at 6 h postoperatively, but there are no differences at 24 and 48 h. Moreover, this early inferiority does not translate to worse functional outcomes at any time point. FNB is associated with better pain control at 6, 24 and 48 h after surgery, while ACB presents the highest cumulative opioid requirement. CLINICAL TRIAL REGISTRATION: This study was registered in clinicaltrials.gov (NCT03518450; https://clinicaltrials.gov/ct2/show/NCT03518450 ; submitted March 17, 2018).

Effectiveness of the muscle energy technique on postpartum meralgia paresthetica: A randomized controlled trial.

BACKGROUND: The effectiveness of the muscle energy technique (MET) on postpartum meralgia paresthetica (MP) affecting the lateral femoral cutaneous nerve is unknown. OBJECTIVE: To investigate the effectiveness of the MET on postpartum MP affecting the lateral femoral cutaneous nerve. METHODS: In this randomized controlled trial, 30 patients with postpartum MP were randomly allocated to study and control groups. The study group received the MET with conventional therapeutic exercises and the control group received the conventional exercises alone for four weeks (thrice a week, for 30-40 minutes duration). Lateral femoral cutaneous nerve distal latency, pain intensity, response to the prone knee bend (PKB) test and pelvic compression test were assessed. RESULTS: Patients allocated to the MET group had improvements compared to the controls in pain intensity (MD: -1.66, 95%CI -2.39 to -0.94), distal latency (MD: -0.66, 95%CI -0.94 to -0.36), and knee range of motion in the PKB test (MD: 19.5∘, 95%CI 13 to 26.1) with high treatment effects, Cohen's d -ES = 1.71, 1.86 and 2.24 respectively. However, there was no between-group difference for the pelvic compression test (p= 0.41). CONCLUSION: The MET can reduce pain, distal latency, and increase the prone knee range of motion in women with MP affecting the lateral femoral cutaneous nerve.

Pain reduction method in recording F-waves from the vastus lateralis muscle.

INTRODUCTION/AIMS: Conventional recording of F-waves from the vastus lateralis muscle causes severe pain in some subjects. Thus, we aimed to investigate the effects of the stimulation frequency on pain and F-wave parameters when recording F-waves from this muscle and to develop a method for recording F-waves from the vastus lateralis muscle that causes minimal pain. METHODS: The subject's femoral nerve was electrically stimulated at 0.5 or 0.2 Hz 30 times, while F-waves were recorded from the vastus lateralis muscle. Pain intensity was measured immediately using a visual analog scale. In addition, the visual analog scale, F-wave persistence, F-wave latency, and F/M amplitude ratio were compared between F-wave recordings with 0.5-Hz electrical stimulation and those with 0.2-Hz electrical stimulation. RESULTS: Eleven healthy men participated in this study. The visual analog scale and F-wave persistence decreased when electrical stimulation at 0.2 Hz was applied compared with electrical stimulation at 0.5 Hz. DISCUSSION: Electrical stimulation at 0.5 Hz increased pain due to temporal summation. However, electrical stimulation at 0.2 Hz did not cause temporal summation, suggesting reduced pain and excitability of the alpha motor neuron pool.

Preferential regeneration and collateral dynamics of motor and sensory neurons after nerve injury in mice.

Specificity in regeneration after peripheral nerve injuries is a major determinant of functional recovery. Unfortunately, regenerating motor and sensory axons rarely find their original pathways to reinnervate appropriate target organs. Although a preference of motor axons to regenerate towards the muscle has been described, little is known about the specificity of the heterogeneous sensory populations. Here, we propose the comparative study of regeneration in different neuron subtypes. Using female and male reporter mice, we assessed the regenerative preference of motoneurons (ChAT-Cre/Ai9), proprioceptors (PV-Cre/Ai9), and cutaneous mechanoreceptors (Npy2r-Cre/Ai9). The femoral nerve of these animals was transected above the bifurcation and repaired with fibrin glue. Regeneration was assessed by applying retrograde tracers in the distal branches of the nerve 1 or 8 weeks after the lesion and counting the retrotraced somas and the axons in the branches. We found that cutaneous mechanoreceptors regenerated faster than other populations, followed by motoneurons and, lastly, proprioceptors. All neuron types had an early preference to regenerate into the cutaneous branch whereas, at long term, all neurons regenerated more through their original branch. Finally, we found that myelinated neurons extend more regenerative sprouts in the cutaneous than in the muscle branch of the femoral nerve and, particularly, that motoneurons have more collaterals than proprioceptors. Our findings reveal novel differences in regeneration dynamics and specificity, which indicate distinct regenerative mechanisms between neuron subtypes that can be potentially modulated to improve functional recovery after nerve injury.

Quadriceps muscle stimulation evokes heteronymous inhibition onto soleus with limited Ia activation compared to femoral nerve stimulation.

Heteronymous excitatory feedback from muscle spindles and inhibitory feedback from Golgi tendon organs and recurrent inhibitory circuits can influence motor coordination. The functional role of inhibitory feedback is difficult to determine, because nerve stimulation, the primary method used in humans, cannot evoke inhibition without first activating the largest diameter muscle spindle axons. Here, we tested the hypothesis that quadriceps muscle stimulation could be used to examine heteronymous inhibition more selectively when compared to femoral nerve stimulation by comparing the effects of nerve and muscle stimulation onto ongoing soleus EMG held at 20% of maximal effort. Motor threshold and two higher femoral nerve and quadriceps stimulus intensities matched by twitch evoked torque magnitudes were examined. We found that significantly fewer participants exhibited excitation during quadriceps muscle stimulation when compared to nerve stimulation (14-29% vs. 64-71% of participants across stimulation intensities) and the magnitude of heteronymous excitation from muscle stimulation, when present, was much reduced compared to nerve stimulation. Muscle and nerve stimulation resulted in heteronymous inhibition that significantly increased with increasing stimulation evoked torque magnitudes. This study provides novel evidence that muscle stimulation may be used to more selectively examine inhibitory heteronymous feedback between muscles in the human lower limb when compared to nerve stimulation.

Is Femoral Nerve Block Superior to Fascia Iliac Block in Hip Surgery? Meta-Analysis of Randomized Controlled Trials.

Background: Femoral nerve block (FNB) and fascia iliac compartment block (FICB) are alternative methods of pain relief during hip surgery. Nevertheless, the effectiveness and safety of FNB compared with FICB are yet to be fully determined. Methods: Electronic databases were systematically searched. Only randomized controlled trials (RCTs) on hip surgery were included. Postoperatively, the pain scores at different time points, narcotic requirements in 24 h, mean arterial pressure, spinal anesthesia (SA) time, patient satisfaction, and adverse effect rates between the two groups were extracted throughout the study. Results: Fourteen RCTs including 1179 patients were included. Compared to the FICB, FNB decreased the VAS scores postoperatively at 24 h at rest (P < 0.05) and the incidence rate of some side effects (nausea, vomiting, and sedation) (P < 0.05). However, compared to the FICB, no significant difference was found in the FNB regarding the VAS scores postoperatively at any of the other time points (2 min, 20 min, 2 h, 24 h at movement, 48 h at rest, and 48 h at movement). Patients in both groups had similar narcotic needs after 24 h, mean arterial pressure, SA time, and patient satisfaction (P > 0.05). Conclusions: FNB has more advantages in reducing VAS scores postoperatively at 24 h at rest and the odds of some adverse effects. A better quality RCT is needed to properly compare FNB with FICB.

Optimal stimulation site of the femoral nerve to record F waves from the vastus lateralis muscle.

INTRODUCTION/AIMS: The conventional recording of F waves from the vastus lateralis muscle (VL) may not accurately measure the F-wave amplitude, as the F-wave latency is short and overlaps with the M wave. However, the optimal stimulation site of the femoral nerve for recording M and F waves separately from the VL remains unclear. In this study we aimed to determine the optimal stimulation site of the femoral nerve to record M and F waves separately from the VL. METHODS: Stimulating electrodes were placed medial and lateral to the VL (50%, 60%, 70%, and 80% of the distance along a line extending from the proximal to the distal thigh). Each site of the distal thigh was electrically stimulated at random and F waves were recorded from the VL. Each stimulation site was considered to be success if there was no severe pain or discomfort during electrical stimulation of the femoral nerve and no overlap between the recorded M and F waves; otherwise, it was determined as a failure. RESULTS: Thirteen healthy men participated in the study. F waves were successfully recorded in five participants at the 50% sites, eight participants at the 60% site, and 12 participants at the 70% and 80% sites. In cases of failed F-wave measurement, the participants experienced severe pain or discomfort due to electrical stimulation. DISCUSSION: M and F waves could be recorded separately from the VL when the relevant branch of the femoral nerve was stimulated in the distal thigh.

Functional outcome and complication following THA through modified direct anterior approach correlated to cadaveric study: are there any differences in Asian hip?

BACKGROUND: Direct anterior approach (DAA) has several advantages including shorter length of hospital stay, faster recovery, and better functional outcome while this approach may cause damage to the lateral femoral cutaneous nerve (LFCN) as high as 81% in the works of literature. Not much data has identified the LFCN pattern in the Asian population. Therefore, the purpose of our study was to identify characteristics of the LFCN patterns representing an Asian hip, which would aid to provide the most appropriate incision of modified direct anterior approach (MDAA) for total hip arthroplasty (THA), and to identify the clinical outcome and complications following THA through MDAA correlated with cadaveric hip in the Asian population. METHODS: After IRB approval, a cadaveric study was done to identify pattern and course of the LFCN in Asian population. The MDAA defined as the incision 2 fingerbreadths posteriorly to anterior superior iliac spine to avoid injury to the LFCN. The clinical phase identified 32 patients who underwent THA because of late-stage osteoarthritis of the hip. The anterolateral skin numbness was measured along tensor fascia lata between 2 weeks until 2 years. The functional outcome assessed by Harris Hip Score (HHS) and complications were evaluated in all patients. RESULTS: The characteristics of the LFCN from cadaveric study (phase 1) was predominantly in sartorius type (60.0%) followed by posterior type (26.6%), fan type (6.7%), and variant type (6.7%). The clinical phase demonstrated that 23 patients (71.9%) had no numbness while 9 patients (28.1%) came with numbness after undergoing THA through the MDAA. Finally, a small area of skin numbness remained in only 3 patients (9.4%) at 2 years follow-up. Additionally, there was no significant difference in functional score at 2 years follow-up (89.0 vs 91.2, p = 0.422) between those with LFCN injury and those without LFCN injury. CONCLUSIONS: The LFCNs were divided into four types. Modified direct anterior approach, which is an alternative approach for THA, allowing for a lower rate of skin numbness and faster recovery without hip dislocation, abductor weakness, and serious nerve complication. Functional outcome was comparable with and without LFCN injury. LEVEL OF EVIDENCE: Level II, prospective observation study.

Effect of race distance on performance fatigability in male trail and ultra-trail runners.

The etiology of changes in lower-limb neuromuscular function, especially to the central nervous system, may be affected by exercise duration. Direct evidence is lacking as few studies have directly compared different race distances. This study aimed to investigate the etiology of deficits in neuromuscular function following short versus long trail-running races. Thirty-two male trail runners completed one of five trail-running races as LONG (>100 km) or SHORT (<60 km). Pre- and post-race, maximal voluntary contraction (MVC) torque and evoked responses to electrical nerve stimulation during MVCs and at rest were used to assess voluntary activation and muscle contractile properties of knee-extensor (KE) and plantar-flexor (PF) muscles. Transcranial magnetic stimulation (TMS) was used to assess evoked responses and corticospinal excitability in maximal and submaximal KE contractions. Race distance correlated with KE MVC (ρ = -0.556) and twitch (ρ = -0.521) torque decreases (p ≤ .003). KE twitch torque decreased more in LONG (-28 ± 14%) than SHORT (-14 ± 10%, p = .005); however, KE MVC time × distance interaction was not significant (p = .073). No differences between LONG and SHORT for PF MVC or twitch torque were observed. Maximal voluntary activation decreased similarly in LONG and SHORT in both muscle groups (p ≥ .637). TMS-elicited silent period decreased in LONG (p = .021) but not SHORT (p = .912). Greater muscle contractile property impairment in longer races, not central perturbations, contributed to the correlation between KE MVC loss and race distance. Conversely, PF fatigability was unaffected by race distance.

Multimodal analgesia protocol for pain management after total knee arthroplasty: comparison of three different regional analgesic techniques.

OBJECTIVES: To evaluate three different analgesic techniques, continuous epidural analgesia (EA), continuous intra-articular (IA) infusion analgesia and continuous femoral nerve block (FNB) in postoperative pain management, length of hospital stay (LOS), and time of patient mobilization after total knee arthroplasty (TKA). METHODS: Seventy-two patients undergoing TKA were randomly allocated into three groups according to the analgesic technique used for postoperative pain management. Group EA patients received epidural analgesia (control group), group IA received intra-articular infusion and group FNB received femoral nerve block. RESULTS: Upon analyzing the Numerical Rating Scale (NRS) scores at rest, at passive and active movement, up to 3 days postoperatively, we observed no statistically significant differences at any time point among the three groups. Similarly, no association among these analgesic techniques (EA, IA, FNB) was revealed regarding LOS. However, significant differences emerged concerning the time of mobilization. Patients who received IA achieved earlier mobilization compared to FNB and EA. CONCLUSIONS: Both IA and FNB generate similar analgesic effect with EA for postoperative pain management after TKA. However, IA appears to be significantly more effective in early mobilization compared to EA and FNB. Finally, no clinically important differences could be detected regarding LOS among the techniques studied.

Usefulness of lateral femoral cutaneous nerve block in combination with femoral nerve block for anterior cruciate ligament reconstruction: a prospective trial.

INTRODUCTION: The study aimed to compare the combination of femoral nerve block (FNB) with interspace between the popliteal artery and the capsule of posterior knee (IPACK) block (IPACK group) with the combination of FNB with lateral femoral cutaneous nerve (LFCN) block (LFCN group) for postoperative pain control in patients undergoing anterior cruciate ligament (ACL) reconstruction. We hypothesized that the lower pain scores and decreased suppository use would be noted in patients administered a combination of FNB and IPACK block. MATERIALS AND METHODS: A non-randomized prospective controlled clinical trial was conducted. The IPACK and LFCN groups included 40 patients each. The patients received IPACK block and LFCN block alternately. Thirty minutes prior to the surgery and after administration of general anesthesia, patients received an ultrasound-guided FNB and IPACK block or LFCN block. After ACL reconstruction, the visual analog scale pain scores were recorded at 30 min, 4 h, 8 h, 12 h, 24 h, 48 h, and 72 h after the surgery. The administration and use of analgesic suppositories were assessed. These measures were compared among the treatment types at each time-point using the Welch's t-test. RESULTS: Suppository use was significantly less in the LFCN group than in the IPACK group. The pain scores were significantly lower in the LFCN group at 30 min, 4 h, 48 h, and 72 h after the surgery. CONCLUSION: The combination of FNB with LFCN block during ACL reconstruction significantly reduces pain in the early postoperative period compared to a combination of FNB with IPACK block. LEVEL OF EVIDENCE: Prospective control trial, Level II.

Prior Upper Body Exercise Impairs 4-km Cycling Time-Trial Performance Without Altering Neuromuscular Function.

Purpose: This study investigated the effects of previous exhaustive upper body exercise on performance and neuromuscular fatigue following a 4-km cycling time-trial (4-km TT). Methods: Eight recreational cyclists performed a 4-km TT with (ARMPRE) or without (CONTR) a previous arm-crank maximal incremental test. In each experimental session, neuromuscular fatigue was evaluated with a series of electrically evoked and maximal voluntary isometric contractions (MVC). Oxygen uptake ( V ˙ O2), heart rate, electromyographic muscle activity (EMGRMS) and rating of perceived exertion (RPE) were also recorded throughout the 4-km TT. Results: The average power output during the 4-km TT was reduced (P = .027) for the ARMPRE (299 ± 59 W) group, compared with CONTR (310 ± 59 W) and overall performance in 4-km TT was impaired (P = .021) in ARMPRE (382 ± 28 s) compared with CONTR (376 ± 27 s). The decrease observed in MVC (P = .033) and potentiated peak twitch force (P = .004) at post-TT were similar between the ARMPRE and CONTR conditions (P = .739 and P = .493, respectively). There was no (P = .619) change in voluntary activation at post-TT between conditions. V ˙ O2, EMGRMS and RPE measured throughout the 4-km TT were not significantly different between the conditions (P = .558, P = .558 and P = .940, respectively). The rate of RPE change relative to power output average and heart rate was higher (P = .030 and P = .013, respectively) in ARMPRE (0.031 ± 0.018 AU/W and 168 ± 8 bpm) than CONTR (0.022 ± 0.010 AU/W and 161 ± 7 bpm). Conclusion: These results suggest that impaired performance in ARMPRE was mostly due to pronounced perception of effort rather than neuromuscular fatigue.

Altered Position Sense after Submaximal Eccentric Exercise-inducing Central Fatigue.

PURPOSE: The purpose of this study was to concomitantly investigate the acute and delayed effects of a submaximal eccentric-induced muscle fatigue on the position sense and the neuromuscular function of the right knee extensor muscles. METHODS: Thirteen young and physically active participants performed a unilateral isokinetic eccentric exercise of their right lower limb until a decrease in maximal voluntary isometric contraction (MVIC) of 20% was reached. Neuromuscular (i.e., MVIC, voluntary activation (VA) level, and evoked contractile properties [DB100 and DB10]) and psychophysical evaluations (i.e., bilateral position-matching task, perceived muscle soreness, and perceived fatigue) were performed at four time points: before (PRE), immediately after (POST), 24 (POST24), and 48 (POST48) the exercise. RESULTS: The acute 20% MVIC reduction (P < 0.001) was associated with both central (i.e., -13% VA decrease, P < 0.01) and peripheral (i.e., -18% and -42% reduction of DB100 and DB10, respectively, P < 0.001) fatigue. In the following days (POST24 and POST48), VA levels had recovered despite the presence of a persisting peripheral fatigue and delayed-onset muscle soreness. Knee position sense, as revealed by position errors, was significantly altered only at POST (P < 0.05) with participants overestimating the length of their knee extensor. Position errors and VA deficits were significantly correlated at POST (r = -0.60, P = 0.03). Position errors returned to nonsignificant control values in the following days. CONCLUSION: The acute central fatigue induced by the eccentric exercise contributes to the position sense disturbances. Central fatigue might lead to alterations in the sensory structures responsible for the integration and the processing of position-related sensory inputs.

Ischemic Preconditioning Blunts Loss of Knee Extensor Torque Complexity with Fatigue.

INTRODUCTION: Neuromuscular fatigue reduces the temporal structure, or complexity, of muscle torque output, purportedly through an effect on motor unit behavior. Ischemic preconditioning (IPC), an emerging ergogenic aid, has been demonstrated to have a potent effect on muscular output and endurance. We therefore tested the hypothesis that IPC would attenuate the fatigue-induced loss of muscle torque complexity. METHODS: Ten healthy participants (6 males/4 females) performed intermittent isometric knee extension contractions (6 s contraction, 4 s rest) to task failure at 40% maximal voluntary contraction. Contractions were preceded by either IPC (three bouts of 5 min proximal thigh occlusion at 225 mm Hg, interspersed with 5 min rest) or SHAM (as IPC, but occlusion at only 20 mm Hg) treatments. Torque and EMG signals were sampled continuously. Complexity and fractal scaling were quantified using approximate entropy (ApEn) and the detrended fluctuation analysis (DFA) α scaling exponent. Muscle oxygen consumption (mV˙O2) was determined using near-infrared spectroscopy. RESULTS: IPC increased time to task failure by 43% ± 13% (mean ± SEM, P = 0.047). Complexity decreased in both trials (decreased ApEn, increased DFA α; both P < 0.001), although the rate of decrease was significantly lower after IPC (ApEn, -0.2 ± 0.1 vs -0.4 ± 0.1, P = 0.013; DFA α, 0.2 ± 0.1 vs 0.3 ± 0.1, P = 0.037). Similarly, the rates of increase in EMG amplitude (P = 0.022) and mV˙O2 (P = 0.043) were significantly slower after IPC. CONCLUSION: These results suggest that the ergogenic effect of IPC observed here is of neural origin and accounts for the slowing of the rates of change in torque complexity, EMG amplitude, and mV˙O2 as fatigue develops.