Is the clinical cervical extensor endurance test capable of differentiating the local and global muscles?

BACKGROUND CONTEXT

Differential alterations have been reported in the local and global cervical muscles in the presence of chronic neck pain (CNP), including the endurance alterations of these muscles. Identifying the involved muscles is crucial to the assessment and rehabilitation of patients with CNP.

PURPOSE

To assess the relationship between clinical endurance test results, pain and disability indices, and ultrasonographic (US) measurements of the neck extensor muscles; to compare the deep and superficial cervical extensor muscle endurance and size of CNP patients with those of asymptomatic subjects and to compare the relationship between local and global extensor endurance with US measures, pain intensity, and disability.

STUDY DESIGN/SETTING

Cross-sectional correlational analysis with a case-control design.

PATIENT SAMPLE

Thirty patients with CNP and 30 asymptomatic subjects participated in this study.

OUTCOME MEASURES

Endurance, thickness, cross-sectional area, and shape ratio of the cervical extensor muscles (splenius capitis [SpCap], semispinalis capitis [SSCap], semispinalis cervicis [SSCer], and multifidus [MF]); pain intensity measured by the visual analog scale (VAS); neck disability index (NDI); correlation between US measures, pain intensity and NDI and extensor endurance; and correlation of US measures with pain intensity and NDI.

METHODS

The deep and superficial cervical extensor muscle endurance and dimensions were measured via a clinical test and by US, respectively. Participants were asked to hold the neutral chin-tuck position while lying prone. The test would be terminated if the head moved into either flexion or extension, which would yield "global" or "local" extensor muscle endurance, respectively.

RESULTS

The CNP patients showed lower global extensor endurance levels than the control participants (p<.05). The US measures of the deep extensor muscles were also smaller in the CNP group (p<.05). There were no significant correlations between extensor endurance test results and US measures in either group except for the SSCap muscle size with local and total endurance (p=.04 for both) of CNP and control participants, respectively. NDI was correlated with SpCap and SSCer muscle thicknesses in a positive and negative manner, respectively (p=.03 for both). There was also a significant correlation between MF size and VAS (p<.05).

CONCLUSIONS

The findings showed higher levels of global muscle fatigability and smaller size of deep neck extensor muscles in CNP patients. Disability and extensor endurance were found to be associated with extensor muscle size. The results challenge the validity of the clinical extensor muscle endurance test in the differentiation of the deep and superficial extensor muscle endurance and the use of US in the assessment of cervical muscle endurance. Further investigations are needed to judge the superficial and deep muscle endurance in CNP patients.

A survey of sensor devices: use in sports biomechanics

This paper examines the use of sensor devices in sports biomechanics, focusing on current frequency of use of Electromyography (EMG) device preferences. Researchers in the International Society of Biomechanics in Sports were invited to participate in an online survey. Responses on multiple sensor devices highlighting frequency of use, device features and improvements researchers sought in acquisition and analysis methods were obtained via an online questionnaire. Results of the investigation showed that the force platform is the most frequently used device, with inertial measurement units and EMG devices growing in popularity. Wireless functionality and ease of use for both the participant and the practitioner proved to be important features. The main findings of the survey demonstrated need for a simple, low power, multi-channel device which incorporates the various sensors into one single device. Biomechanists showed they were looking for more availability of wireless sensor devices with acquisition and analysis features. The study found there is a need to develop software analysis tools to accompany the multi-channel device, providing all the basic functions while maintaining compatibility with existing systems.

The effect of a physiological concentration of caffeine on the endurance of maximally and submaximally stimulated mouse soleus muscle

The use of caffeine as an ergogenic aid to promote endurance has been widely studied, with human literature showing the greatest benefit during submaximal muscle activities. Recent evidence suggests that the acute treatment of skeletal muscle with physiological concentrations of caffeine (70 μM maximum) will directly potentiate force production. The aims of the present study are: firstly, to assess the effects of a physiological concentration (70 μM) of caffeine on endurance in maximally activated mouse soleus (relatively slow) muscle; and secondly, to examine whether endurance changes when muscle is activated submaximally during caffeine treatment. Maximally stimulated soleus muscle treated with 70 μM caffeine resulted in a significant (17.6 %) decrease in endurance. In contrast, at a submaximal stimulation frequency, caffeine treatment significantly prolonged endurance (by 19.2 %). Findings are activation-dependent such that, during high frequency stimulation, caffeine accelerates fatigue, whereas, during low frequency stimulation, caffeine delays fatigue.

Effects of repeated ankle plantar-flexions on H-reflex and body sway during standing

The study investigated relations between effects of repeated ankle plantar-flexion movements exercise on the soleus Hoffmann (H) reflex and on postural body sway when maintaining upright stance. Ten young volunteers performed five sets of ankle plantar-flexions of both lower limbs. Assessment of the feet centre-of-pressure (COP) displacement and H-reflex tests were carried out in quiet stance before, during and after the exercise. H-max and M-max responses were obtained in 8 subjects and reported as the peak-to-peak amplitudes of the right soleus muscle electromyographic waves. Mean dispersion of COP along the antero-posterior direction increased significantly during the exercise; whilst the overall H-reflex response indicated a reduction without a concomitant modification in the M-max response. H-reflex responses, however, varied between participants during the first sets of exercise, showing two main trends of modulation: either depression or early facilitation followed by reduction of the H-reflex amplitude. The extent of reflex modulation in standing position was correlated to the concentric work performed during the exercise (r=0.85; p<0.01), but not to the antero-posterior COP dispersion. These results suggest that during a repeated ankle plantar-flexions exercise, modulation of the H-reflex measured in upright stance differs across individuals and is not related to changes of postural sway.