Increased resistance towards fatigability in patients with facioscapulohumeral muscular dystrophy

Abstract Purpose In facioscapulohumeral muscular dystrophy (FSHD) fatigue is a major complaint. We aimed to investigate whether during isometric sustained elbow flexions, performance fatigability indexes differ in patients with FSHD with respect to healthy controls. Methods Seventeen patients with FSHD and seventeen healthy controls performed two isometric flexions of the dominant biceps brachii at 20% of their maximal voluntary contraction (MVC) for 2 min and then at 60% MVC until exhaustion. Muscle weakness was characterized as a percentage of predicted values. Maximal voluntary strength, endurance time and performance fatigability indices (mean frequency of the power spectrum (MNF), muscle fiber conduction velocity (CV) and fractal dimension (FD)), extracted from the surface electromyogram signal (sEMG) were compared between the two groups. Results In patients with FSHD, maximal voluntary strength was 68.7% of predicted value (p < 0.01). Compared to healthy controls, FSHD patients showed reduced MVC (p < 0.001; r = 0.62) and lower levels of performance fatigability, characterized by reduced rate of changes in MNF (p < 0.01; r = 0.56), CV (p < 0.05; 0.37) and FD (p < 0.001; r = 0.51) and increased endurance time (p < 0.001; r = 0.63), during the isometric contraction at 60% MVC. Conclusion A decreased reduction in the slopes of all the considered sEMG parameters during sustained isometric elbow flexions suggests that patients with FSHD experience lower levels of performance fatigability compared to healthy controls.

Download Full-text

Comparison of Endurance Time Prediction of Biceps Brachii Using Logarithmic Parameters of a Surface Electromyogram during Low-Moderate Level Isotonic Contractions

Applied Sciences ◽

10.3390/app11062861 ◽

2021 ◽

Vol 11 (6) ◽

pp. 2861

Author(s):

Chang-ok Cho ◽

Jin-Hyoung Jeong ◽

Yun-jeong Kim ◽

Jee Hun Jang ◽

Sang-Sik Lee ◽

...

Keyword(s):

Biceps Brachii ◽

Maximum Voluntary Contraction ◽

Voluntary Contraction ◽

Endurance Capacity ◽

Mean Power ◽

Mean Power Frequency ◽

Spectral Parameters ◽

Endurance Time ◽

Surface Electromyogram ◽

Isotonic Contractions

At relatively low effort level tasks, surface electromyogram (sEMG) spectral parameters have demonstrated an inconsistent ability to monitor localized muscle fatigue and predict endurance capacity. The main purpose of this study was to assess the potential of the endurance time (Tend) prediction using logarithmic parameters compared to raw data. Ten healthy subjects performed five sets of voluntary isotonic contractions until their exhaustion at 20% of their maximum voluntary contraction (MVC) level. We extracted five sEMG spectral parameters namely the power in the low frequency band (LFB), the mean power frequency (MPF), the high-to-low ratio between two frequency bands (H/L-FB), the Dimitrov spectral index (DSI), and the high-to-low ratio between two spectral moments (H/L-SM), and then converted them to logarithms. Changes in these ten parameters were monitored using area ratio and linear regressive slope as statistical predictors and estimating from onset at every 10% of Tend. Significant correlations (r > 0.5) were found between log(Tend) and the linear regressive slopes in the logarithmic H/L-SM at every 10% of Tend. In conclusion, logarithmic parameters can be used to describe changes in the fatigue content of sEMG and can be employed as a better predictor of Tend in comparison to the raw parameters.

Download Full-text

Changes in muscle activation can prolong the endurance time of a submaximal isometric contraction in humans

Journal of Applied Physiology ◽

10.1152/japplphysiol.00635.2002 ◽

2003 ◽

Vol 94 (1) ◽

pp. 108-118 ◽

Cited By ~ 84

Author(s):

Sandra K. Hunter ◽

Roger M. Enoka

Keyword(s):

Isometric Contraction ◽

Muscle Activation ◽

Voluntary Contraction ◽

Endurance Time ◽

Force Fluctuations ◽

Rate Of Increase ◽

Before And After ◽

Young Subjects ◽

Reduced Rate ◽

Fatiguing Contractions

Fourteen young subjects (7 men and 7 women) performed a fatiguing isometric contraction with the elbow flexor muscles at 20% of maximal voluntary contraction (MVC) force on three occasions. Endurance time for session 3 [1,718 ± 1,189 (SD) s] was longer than for session 1 (1,225 ± 683 s) and session 2 (1,410 ± 977 s). Five men and four women increased endurance time between session 1 and 3 by 60 ± 28% (responders), whereas two men and three women did not (−3 ± 11%; nonresponders). The MVC force was similar for the responders and nonresponders, both before and after the fatiguing contraction. Fatiguing contractions were characterized by an increase in the electromyogram (EMG) amplitude and number of bursts during the fatiguing contractions. The responders achieved a similar level of EMG at exhaustion but a reduced rate of increase in the EMG across sessions. The rate of increase in EMG across sessions declined for the nonresponders, but it remained greater than that of the responders. The increase in burst rate during the contractions declined across sessions with a negative relation between burst rate and endurance time ( r = −0.42). Normalized force fluctuations increased during the fatiguing contractions, and there was a positive relation ( r = 0.60) between the force fluctuations and burst rate. Changes in mean arterial pressure and heart rate during the fatiguing contraction were similar for the responders and nonresponders across the three sessions. The results indicate that those subjects who increased the endurance time of a submaximal contraction across three sessions did so by altering the level and pattern of muscle activation.

Download Full-text

Muscle Fiber Conduction Velocity Correlates With the Age at Onset in Mild FSHD Cases

Frontiers in Physiology ◽

10.3389/fphys.2021.686176 ◽

2021 ◽

Vol 12 ◽

Author(s):

Matteo Beretta-Piccoli ◽

Massimo Negro ◽

Luca Calanni ◽

Angela Berardinelli ◽

Gabriele Siciliano ◽

...

Keyword(s):

Conduction Velocity ◽

Biceps Brachii ◽

Molecular Genetic ◽

Age At Onset ◽

Significant Negative Correlation ◽

Facioscapulohumeral Muscular Dystrophy ◽

Voluntary Contraction ◽

Semg Signal ◽

Disability Score ◽

Muscle Involvement

A majority of patients with facioscapulohumeral muscular dystrophy (FSHD) report severe fatigue. The aim of this study was to explore whether fatigability during a performance task is related to the main clinical features of the disease in mildly affected patients. A total of 19 individuals with a molecular genetic-based diagnosis of FSHD (median D4Z4 deletion length of 27 kb) performed two isometric flexions of the dominant biceps brachii at 20% of their maximal voluntary contraction (MVC) for 2 min, and then at 60% MVC until exhaustion. Fatigability indices (average rectified value, mean frequency, conduction velocity, and fractal dimension) were extracted from the surface electromyogram (sEMG) signal, and their correlations with age, age at onset, disease duration, D4Z4 contraction length, perceived fatigability, and clinical disability score were analyzed. The conduction velocity during the low level contraction showed a significant negative correlation with the age at onset (p < 0.05). This finding suggest the assessment of conduction velocity at low isometric contraction intensities, as a potential useful tool to highlight differences in muscle involvement in FSHD patients.

Download Full-text