Hand grip strength and fatigability: correlation with clinical parameters and diagnostic suitability in ME/CFS

BACKGROUND

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a complex and debilitating disease accompanied by muscular fatigue and pain. A functional measure to assess muscle fatigability of ME/CFS patients is, however, not established in clinical routine. The aim of this study is to evaluate by assessing repeat maximum handgrip strength (HGS), muscle fatigability as a diagnostic tool and its correlation with clinical parameters.

METHODS

We assessed the HGS of 105 patients with ME/CFS, 18 patients with Cancer related fatigue (CRF) and 66 healthy controls (HC) using an electric dynamometer assessing maximal (Fmax) and mean force (Fmean) of ten repetitive measurements. Results were correlated with clinical parameters, creatinine kinase (CK) and lactate dehydrogenase (LDH). Further, maximum isometric quadriceps strength measurement was conducted in eight ME/CFS patients and eight HC.

RESULTS

ME/CFS patients have a significantly lower Fmax and Fmean HGS compared to HC (p < 0.0001). Further, Fatigue Ratio assessing decline in strength during repeat maximal HGS measurement (Fmax/Fmean) was higher (p ≤ 0.0012). The Recovery Ratio after an identical second testing 60 min later was significantly lower in ME/CFS compared to HC (Fmean2/Fmean1; p ≤ 0.0020). Lower HGS parameters correlated with severity of disease, post-exertional malaise and muscle pain and with higher CK and LDH levels after exertion.

CONCLUSION

Repeat HGS assessment is a sensitive diagnostic test to assess muscular fatigue and fatigability and an objective measure to assess disease severity in ME/CFS.

Quantification of the effect of compression garments on fatigue behavior in cycling

Effectiveness of compression garments to enhance athletic performance is the subject of numerous qualitative studies. This study aims at quantification of the effect of compression garments using nonlinear dynamics approach. Kinematic data of fifteen healthy male athletes was obtained and the state space was reconstructed. The trajectory drifts caused by fatigue in the state space were quantified using local flow variation technique. The study illustrates that compression garments (CGs) decrease rate of fatigue development and the body exhibits a more restricted complexity (more predictable and smaller fluctuations) when CGs are worn.

How to assess the recovery of muscular function following nerve injury: A view from surgeons and patients

Patient experience of motor recovery from denervation paralysis is complex and textured. The Medical Research Council (MRC) system of grading muscle peak volitional force is widely used as a single measure of assessment. However, it is becoming clear that current motor function assessments are not reflecting the patient lived experience of muscle reinnervation. Therefore, this study aimed to engage international expert nerve surgeons in a classical Delphi process to achieve a consensus of opinion on the ideal clinical assessment of motor function. This was compared with patient-reported impairments of reinnervated muscle. Invitations to engage in the Delphi process were extended to expert peripheral nerve surgeons across two international specialist meetings. For comparison, patients who attended a "Nerve Injury Community Day" were invited to complete a questionnaire on patient-reported impairments of reinnervated muscle. Questions were designed on the basis of a literature review and the clinical experiences of a specialist nerve injury unit. A combination of direct yes/no, multiple choice, open-ended and Likert questions were employed throughout the questionnaires. Eighteen surgeons engaged with the Delphi process; 18 and 11 responded to the first and second rounds respectively. Thirty-one patients responded to the questionnaire. It was found that clinicians were strongly biased towards efferent assessments of muscular function, while patients strongly favoured muscular fatigue, co-contraction and pain when monitoring their own recovery. The findings suggest that current clinical assessments of muscular function are inadequate and should embody measurements of afferent muscular function to better reflect the lived experience of muscle reinnervation.

Understanding the effects of beetroot juice intake on CrossFit performance by assessing hormonal, metabolic and mechanical response: a randomized, double-blind, crossover design

BACKGROUND

Acute beetroot juice (BJ) intake has shown to enhance aerobic and anaerobic performance. However, no studies have evaluated the effects of BJ intake on CrossFit (CF) performance by linking hormonal, metabolic, and mechanical responses. The purpose of this study was to determine the causal physiological association between hormonal, metabolic and mechanical responses, and CF workouts performance after acute BJ intake.

METHODS

Twelve well-trained male practitioners undertook a CF workout after drinking 140 mL of BJ (~ 12.8 mmol NO3-) or placebo. The two experimental conditions (BJ or placebo) were administered using a randomized, double-blind, crossover design. The CF workout consisted of repeating the same exercise routine twice: Wall ball (WB) shots plus full back squat (FBS) with 3-min rest (1st routine) or without rest (2nd routine) between the two exercises. A 3-min rest was established between the two exercise routines.

RESULTS

An interaction effect was observed in the number of repetitions performed (p = 0.04). The Bonferroni test determined a higher number of repetitions after BJ than placebo intake when a 3-min rest between WB and FBS (1st routine) was established (p = 0.007). An interaction effect was detected in cortisol response (p = 0.04). Cortisol showed a higher increase after BJ compared to placebo intake (76% vs. 36%, respectively). No interaction effect was observed in the testosterone and testosterone/cortisol ratio (p > 0.05). A significant interaction effect was found in oxygen saturation (p = 0.01). A greater oxygen saturation drop was observed in BJ compared to placebo (p <  0.05). An interaction effect was verified in muscular fatigue (p = 0.03) with a higher muscular fatigue being observed with BJ than placebo (p = 0.02).

CONCLUSIONS

BJ intake improved anaerobic performance only after the recovery time between exercises. This increase in performance in the first routine probably generated greater hypoxia in the muscle mass involved, possibly conditioning post-exercise performance. This was observed with a fall in oxygen saturation and in muscle fatigue measured at the end of the CF workout. The greatest perceived changes in cortisol levels after BJ intake could be attributed to the nitrate-nitrite-nitric oxide pathway.

Effects of a lower limb muscular fatigue on posture-movement interaction during a lower limb pointing task

PURPOSE

The aim of the present study was to investigate the effects of muscular fatigue on the interaction between posture and movement during a lower limb pointing task.

METHODS

Participants (n = 16), aged 18-30 years, kicked a ball toward a target in four conditions of fatigue: No muscular fatigue (NF), fatigue in the kicking (FM) or postural limb (FP) alone, and fatigue in both limbs (FMP). The mean amplitude and speed of the centre of foot pressure (CoP) and centre of mass (CoM) displacements were estimated through a force platform and an optoelectronic system, respectively. In addition, surface electromyography (EMG) of the biceps femoris, rectus femoris, medial gastrocnemius, and peroneus longus was recorded to investigate the anticipatory postural adjustments (APAs).

RESULTS

Muscular fatigue yielded a decreased kicking accuracy (p < 0.001) and an increased time to perform the movement (p < 0.001), mainly during the backswing motion. In addition, significant increases in the mean amplitude and speed of the CoP and CoM displacement were found in the anteroposterior (AP) and mediolateral (ML) axes (ps < 0.001), especially when both limbs were fatigued. The EMG analysis confirmed that fatigue modified the way APAs were generated. During fatigue, postural muscle activity increased, but was delayed with respect to movement onset (ps < 0.001). This pattern of response was more consistent when both limbs were fatigued (p < 0.001).

CONCLUSION

The present results suggested an additive effect of fatigue and a functional adaptation and subsequent decrease in the overall variability of APAs, indicating that postural and motor processes are interdependent.

New joint analysis of electromyography spectrum and amplitude-based methods towards real-time muscular fatigue evaluation during a simulated surgical procedure: A pilot analysis on the statistical significance

The Joint Analysis of Spectral and Amplitude (JASA) method offers a valuable tool for the indication of four muscle conditions in occupational field studies. It has both advantages of an easy computation and an ergonomic display of the results. However, several limitations are pointed out such as the lack of information on the change of the muscle condition all along the completion of task. This paper proposes two evolutions of the JASA method to quantify muscular fatigue in real time for comfort analysis. The evolutionary method focuses on increased time windows; and the sequential method analyses the muscle conditions on constant sliding time lapses. A pilot study is conducted for a minimally-invasive laparoscopic procedure. The outcome results obtained with the original, the evolutionary and the sequential methods are compared. Both new methods provide a complementary analysis of the muscular fatigue over a task and the statistical significance of the condition.

Hand rest and wrist support are effective in preventing fatigue during prolonged typing

STUDY DESIGN

Case series (longitudinal).

INTRODUCTION

Only few reports concerning the efficacy of commonly used strategies for preventing upper limb occupational disorders associated with prolonged typing exist.

PURPOSE OF THE STUDY

We aimed to investigate whether the duration of typing and the use of 2 strategies (hand rest and wrist support) changes muscle physiological response and therefore the electromyography records.

METHODS

We enrolled 25 volunteers, who were unfamiliar with the task and did not have musculoskeletal disorders. The subjects underwent 3 prolonged typing protocols to investigate the efficacy of the 2 adopted strategies in reducing the trapezius, biceps brachii, and extensor digitorum communis fatigue.

RESULTS

Typing for 1 hour induced muscular fatigue (60%-67% of the subjects). The extensor digitorum communis muscle exhibited the highest percentage of fatigue (72%-84%) after 1 and 4 hours of typing (1 hour, P = .04; 4 hours, P = .02). Fatigue levels in this muscle were significantly reduced (24%) with the use of pause typing (4 hours, P = .045), whereas biceps brachii muscle fatigue was reduced (32%) only with the use of wrist supports (P = .02, after 4 hours). Trapezius muscle fatigue was unaffected by the tested occupational strategies (1 hour, P = .62; 4 hours, P = .85).

DISCUSSION

Despite presenting an overall tendency for fatigue detected during the application of the protocols, the assessed muscles exhibited different behavior patterns, depending on both the preventive strategy applied and the muscle mechanical role during the task.

CONCLUSION

Hand rest and wrist support can successfully reduce muscle fatigue in specific upper limb muscles during prolonged typing, leading to a muscle-selective reduction in the occurrence of fatigue and thus provide direct evidence that they may prevent work-related musculoskeletal disorders.

LEVEL OF EVIDENCE

N/A.

The influence of fatigue in evertor muscles during lateral ankle sprain

Ankle sprain in plantarflexion and inversion is one of the most common injuries occurring in daily activities and sports. Although acute symptoms may resolve quickly, many individuals have reported persistent pain and instability. Thus, understanding the factors that contribute to the occurrence of this type of injury is extremely important. Although sprains are multifactorial, a relationship can be established between sprain and fatigue. Therefore, the present study examined the latency and intensity of activation of the peroneus longus and brevis muscles under conditions of fatigue. Twenty-three women participated in the study, including 12 with functional instability of the ankle and 11 without a history of sprain. To induce fatigue, the volunteers maintained the force of eversion and plantarflexion at 70% of the maximum voluntary isometric contraction for as long as possible until a 10% decline in the rated force occurred. Ten simulations of ankle sprains were performed before and after fatigue at random for each side, with simultaneous recordings of the electromyographic signals, using a simulator platform for inversion sprain and plantarflexion. As a result, after fatigue, no change in latency was observed. However, a reduction in the intensity of contraction of the muscles analyzed in both groups was observed. Neuromuscular control was concluded to be compromised in situations of fatigue, while differences in muscle behavior were not observed between stable and unstable ankles.

Physiological and kinematic effects of a soft exosuit on arm movements

BACKGROUND

Soft wearable robots (exosuits), being lightweight, ergonomic and low power-demanding, are attractive for a variety of applications, ranging from strength augmentation in industrial scenarios, to medical assistance for people with motor impairments. Understanding how these devices affect the physiology and mechanics of human movements is fundamental for quantifying their benefits and drawbacks, assessing their suitability for different applications and guiding a continuous design refinement.

METHODS

We present a novel wearable exosuit for assistance/augmentation of the elbow and introduce a controller that compensates for gravitational forces acting on the limb while allowing the suit to cooperatively move with its wearer. Eight healthy subjects wore the exosuit and performed elbow movements in two conditions: with assistance from the device (powered) and without assistance (unpowered). The test included a dynamic task, to evaluate the impact of the assistance on the kinematics and dynamics of human movement, and an isometric task, to assess its influence on the onset of muscular fatigue.

RESULTS

Powered movements showed a low but significant degradation in accuracy and smoothness when compared to the unpowered ones. The degradation in kinematics was accompanied by an average reduction of 59.20±5.58% (mean ± standard error) of the biological torque and 64.8±7.66% drop in muscular effort when the exosuit assisted its wearer. Furthermore, an analysis of the electromyographic signals of the biceps brachii during the isometric task revealed that the exosuit delays the onset of muscular fatigue.

CONCLUSIONS

The study examined the effects of an exosuit on the characteristics of human movements. The suit supports most of the power needed to move and reduces the effort that the subject needs to exert to counteract gravity in a static posture, delaying the onset of muscular fatigue. We interpret the decline in kinematic performance as a technical limitation of the current device. This work suggests that a powered exosuit can be a good candidate for industrial and clinical applications, where task efficiency and hardware transparency are paramount.

Electrophysiology of Muscle Fatigue in Cardiopulmonary Resuscitation on Manikin Model

Cardiopulmonary resuscitation requires the provider to adopt positions that could be dangerous for his or her spine, specifically affecting the muscles and ligaments in the lumbar zone and the scapular spinal muscles. Increased fatigue caused by muscular activity during the resuscitation could produce a loss of quality and efficacy, resulting in compromising resuscitation. The aim of this study was to evaluate the maximum time a rescuer can perform uninterrupted chest compressions correctly without muscle fatigue. This pilot study was performed at Universidad Complutense de Madrid (Spain) with the population recruited following CONSORT 2010 guidelines. From the 25 volunteers, a total of 14 students were excluded because of kyphoscoliosis (4), lumbar muscle pain (1), anti-inflammatory treatment (3), or not reaching 80% of effective chest compressions during the test (6). Muscle activity at the high spinal and lumbar (L5) muscles was assessed using electromyography while students performed continuous chest compressions on a ResusciAnne manikin. The data from force exerted were analyzed according to side and muscle groups using Student's t test for paired samples. The influence of time, muscle group, and side was analyzed by multivariate analyses ( p ≤ .05). At 2 minutes, high spinal muscle activity (right: 50.82 ± 9.95; left: 57.27 ± 20.85 μV/ms) reached the highest values. Activity decreased at 5 and 15 minutes. At 2 minutes, L5 activity (right: 45.82 ± 9.09; left: 48.91 ± 10.02 μV/ms) reached the highest values. After 5 minutes and at 15 minutes, activity decreased. Fatigue occurred bilaterally and time was the most important factor. Fatigue began at 2 minutes. Rescuers exert muscular countervailing forces in order to maintain effective compressions. This imbalance of forces could determine the onset of poor posture, musculoskeletal pain, and long-term injuries in the rescuer.

An ergonomic field study to evaluate the effects of a rotatable handle piece on muscular stress and fatigue as well as subjective ratings of usability, wrist posture and precision during laparoscopic surgery: an explorative pilot study

PURPOSE

The interface between surgeon and the laparoscopic instrument is an important factor in biomechanical stress that may increase the risk of musculoskeletal complaints in surgeons. This article investigates the effect of a laparoscopic instrument with a rotatable handle piece (rot-HP) on muscular stress and fatigue during routine laparoscopic procedures (LP) as well as usability, wrist posture and working precision.

METHODS

40 LP (subtotal hysterectomies) performed by 11 surgeons were investigated. 20 LP were carried out with the rot-HP and 20 with a fixed (standard) laparoscopic handle piece instrument. Shoulder and arm muscle activity was monitored via surface electromyography (sEMG). The electrical activity (EA) and median power frequency (MPF) were used to determine muscular stress and fatigue. Usability, wrist posture, and working precision between handle piece conditions were assessed by a survey.

RESULTS

Using the rot-HP did not reduce muscular stress. A tendency of muscular fatigue (increasing EA, decreasing MPF) occurred in the upper trapezius, middle deltoid and extensor digitorum muscles; however, no differences were found between handle pieces. Wrist posture was more comfortable using the rot-HP and working precision and usability tended to be preferred using the standard handle piece.

CONCLUSIONS

Although wrist posture seemed to be optimized by the rot-HP, no effect on muscular stress and fatigue was observed in routine LP (< 60 min duration). Optimization of wrist posture may provide positive effects in mid- or long-term procedures. However, sufficient familiarization with the new instrument is crucial since working precision and usability could be impaired.

Intense resistance exercise increases peripheral brain-derived neurotrophic factor

OBJECTIVES

Brain-derived neurotrophic factor (BDNF) has been shown to increase in an intensity dependent manner in response to aerobic exercise. However, previous research investigating the use of resistance exercise to increase BDNF levels has been less conclusive, likely due to the low intensity nature of traditional resistance exercise programs. This study examined the influence of acute resistance exercise to-fatigue on serum BDNF levels and blood lactate.

DESIGN

Acute crossover study.

METHODS

Eleven untrained to intermediately trained males (age: 25.0±1.3 year) and five untrained females (age: 23.2±1.1 year) were recruited to undertake two bouts of resistance exercise. Strength (five sets of five repetitions, 180s recovery) and hypertrophy (three sets of ten repetitions, 60s recovery) based resistance exercise was implemented to-fatigue to examine the effect on serum BDNF and blood lactate levels immediately post-, and 30min post-exercise.

RESULTS

An interaction (p<0.01; ES=0.52) was observed between conditions immediately post-exercise, with hypertrophy resulting in significantly greater BDNF levels when compared with strength exercise. Changes in lactate and BDNF from baseline to post- exercise were positively correlated following hypertrophy exercise (r=0.70; p<0.01), but not correlated following strength exercise (r=0.18; p=0.56).

CONCLUSIONS

The use of a to-fatigue hypertrophy based resistance exercise protocol provides the necessary stimulus to increase peripheral serum BDNF. Mechanistically, the presence of lactate does not appear to drive the BDNF response during resistance exercise.

Reduced muscular fatigue after a 12-week leucine-rich amino acid supplementation combined with moderate training in elderly: a randomised, placebo-controlled, double-blind trial

Background

Age-related muscle loss is characterised by a progressing decrease in muscle mass, strength and function. Besides resistance training and physical activity, appropriate nutrition that is rich in protein, especially branched-chain amino acids, is very important to support training effects and positively influence the protein synthesis to degradation ratio.

Aim

The purpose of this study was to evaluate the effect of a 12-week leucine-rich amino acid supplementation in combination with moderate training.

Methods

Forty-eight healthy subjects exercised for 30 min three times per week and received either a leucine-rich amino acid supplementation or a placebo. Before and after supplementation, volunteers performed an exhaustive eccentric exercise protocol. Maximal concentric strength, muscle soreness, creatine kinase (CK), type II collagen collagenase cleavage neoepitope (C2C), C propeptide of type II procollagen (CP2) and safety assessments were performed before exercise and after 3, 24, 48 and 72 hours.

Results

The supplementation with leucine resulted in reduced loss of strength at 0 and 3 hours after downhill walking compared with the placebo (p=0.0439). The reduction of C2C/CP2 ratio deflection was significantly increased (p=0.038) due to leucine compared with the placebo. The same tendency could be observed for the recovery phase. No significant supplement effects for muscle soreness and CK could be observed.

Conclusion

The principle findings show that leucine-rich amino acid supplementation can counteract the negative effects of eccentric exercise. The treatment resulted in a reduction of exercise-induced strength loss.

Detecting fatigue thresholds from electromyographic signals: A systematic review on approaches and methodologies

The aim of the current paper was to systematically review the relevant existing electromyographic threshold concepts within the literature. The electronic databases MEDLINE and SCOPUS were screened for papers published between January 1980 and April 2015 including the keywords: neuromuscular fatigue threshold, anaerobic threshold, electromyographic threshold, muscular fatigue, aerobic-anaerobictransition, ventilatory threshold, exercise testing, and cycle-ergometer. 32 articles were assessed with regard to their electromyographic methodologies, description of results, statistical analysis and test protocols. Only one article was of very good quality. 21 were of good quality and two articles were of very low quality. The review process revealed that: (i) there is consistent evidence of one or two non-linear increases of EMG that might reflect the additional recruitment of motor units (MU) or different fiber types during fatiguing cycle ergometer exercise, (ii) most studies reported no statistically significant difference between electromyographic and metabolic thresholds, (iii) one minute protocols with increments between 10 and 25W appear most appropriate to detect muscular threshold, (iv) threshold detection from the vastus medialis, vastus lateralis, and rectus femoris is recommended, and (v) there is a great variety in study protocols, measurement techniques, and data processing. Therefore, we recommend further research and standardization in the detection of EMGTs.