Effects of resistance training in humans on neck muscle performance, and electromyogram power spectrum changes

Abstract

The purpose of this study was to quantify the neuromuscular cervical adaptations to an 8 week strength training programme. Seven healthy men, with no pathological conditions of the neck, performed a lateral flexion isometric resistance-training programme three times a week. The training sessions consisted of one set of ten contractions, each of 6 s duration, at 60% of the predetermined maximal voluntary isometric torque (MVTim) (warm-up) and two sets of eight contractions, each of 6 s duration, at 80% MVTim. The training effects were evaluated in three ways: muscle size, strength and fatigability. The cross-sectional areas (CSA) of the trapezius (TRP) and sternocleidomastoideus (SCM) muscles were determined using a computerised tomographic scanner. Results showed an increase in the CSA of TRP and SCM muscles after training, 8.8% at C5 level and 6.4% at C7 level for SCM muscle and 12.2% at C7 level for TRP muscle. Strength increased significantly under both isometric and isokinetic conditions (35% and 20%, respectively). Muscle fatigability in lateral flexion was quantified during a sustained isometric contraction at 50% of MVTim. The shift of the mean power frequency of the electromyogram power spectrum density function of SCM muscle toward lower frequencies was less after training (14.6% compared to 6.8%). These results indicate the beneficial effect of a strength-training programme which increases neck muscle size and strength during lateral flexion, and decreases the fatigability of the superficial muscles of the neck.

Specificity in Retraining Craniocervical Flexor Muscle Performance

“…Gains in isometric strength following rehabilita- Craniocervical Flexor Muscle Performance* tion have been correlated with increases in cross-sectional area of neck muscles. 5,31 However, this may not explain the gains in MVC observed for both groups in this study (TABLE), particularly for the CCFEx group, who only ever performed relatively low-intensity exercise. Gains in MVC following only 6 weeks of therapeutic exercise, as performed in this study, may be more associated with neuromuscular adaptations such as greater synchronization of motor units, 4,23 altered sensitivity of muscle receptors, 20 and reduced recruitment of nonprimary muscles.…”

“…18,21,32,33 Although both exercise programs had some characteristics specific to the isometric dynamometry tests, neither were identical, particularly with regard to characteristics such as joint angles, velocity, duration, and intensity of CCF muscle contractions. Additionally, there is also some evidence that isometric tests of muscular function are not sensitive to dynamically induced training adaptations, 31,39 as may have been expected with both exercise programs.…”

Daily titration of neurally adjusted ventilatory assist using the diaphragm electrical activity

“…Daily SBT with PSV 7/0 [pressure support of 7 cmH 2 O and no positive endexpiratory pressure (PEEP)] is a reproducible effort where EAdi can easily be measured. A mean respiratory effort *60% of the value developed during the inspiratory effort could be adapted to prevent respiratory muscle fatigue or limit the incidence of over-assistance [13,14]. Patients in whom PSV 7/0 can be maintained for two consecutive hours are usually extubated [1].…”

Development of a new method of measurement of cranio-cervical flexor muscle performance

“…It was the intention of the CCFD testing protocol to challenge and measure the isometric fu nction of this muscle group over a range of contraction intensities (low to maximal) similar to intensities which could feasibly be fa ced in ordinary daily fu nction. Based on this ideal as well as the evidence provided previously, (Falla et al 2003b ;Gogia and Sabbahi 1994), and at moderate loads (50-60% of IMVC) (Falla et al 2003b ;Gogia and Sabbahi 1994;Randlov et al 1998;Portero et al 2001) have been previously reported for cervical muscle fat igue studies. Studies investigating muscle fa tigue in other regions of the body have also used similar sub-maximal sustained contraction intensities (Duchateau and Hainaut 1993;Duchateau et al 2002;Hunter et al 2002;Hunter et al 2004).…”