Muscle tone in different joint positions and at submaximal isometric torque levels

Abstract

The aim was to evaluate the tone and electric activity of the quadriceps muscle at rest and different torque levels. The second aim was to study whether thickness of soft tissues and change in the joint position would affect muscle tone. Eighteen healthy subjects participated. Computerized muscle tonometer (CMT) and surface electromyography (sEMG) measurements were performed: seated, first at rest with leg straight and then with the knee at 60 degrees . Thereafter measurements were obtained at levels of 80, 60, 40 and 20% of the maximum isometric torque at the same knee angle. Thickness of skin, subcutis and muscle was measured by ultrasound. The CMT values taken were the depth the indenter travelled and the work it did while compressing the right rectus femoris and vastus intermedius muscles. Expressed as mean (SD) depth the change in muscle tone changed from 29.2 (3.6) mm in the relaxed position to 16.9 (5.2) mm at 80% of maximal torque, and expressed as work the values were from 1589 (150) mJ to 739 (149) mJ respectively. The correlation between CMT, sEMG and torque measurements varied from r = -0.52 to -0.71 (p < 0.01). CMT was able to detect a change of 20% in torque production and 4% in tone. Tone values, at each torque level, were significantly separate from the values at the other force levels (p < 0.001-0.04). Soft tissue thickness explained most of the tone results at rest (57%). The repeatability of the CMT measures was good (ICCs 0.75-0.99). Both depth and work correlated with electric activity and muscle torque, but the correlation with work was higher. In conclusion, muscle activity, length and thickness have to be taken into account when evaluating muscle tone.

Responsiveness of Muscle Tone Characteristics to Progressive Force Production

“…This study is in keeping with previous studies reporting that muscle compliance (tissue displacement) measurements performed perpendicularly to the tissue are sensitive to changes in muscle activation levels (1,2,11,14,20). Alamaki et al (1) found that when muscle torque increased from 0 to 80% of MVC, the compliance decreased by 48%, and the torque and compliance correlated significantly (r = 20.67, p , 0.001). In this study, the change from 0 to 80% of MVC was even larger, 66%.…”

“…Many factors affect the level of muscle tone, such as muscle structure (9,17,29) intramuscular pressure (17), pain (39), temperature (18,27), preceding rest or exercise (28,34), diseases (19,25,31,32), and medication (30,35). During contraction the muscle tone changes depending on level of force production, muscle length, and speed of contraction (1,5,8,26).…”

“…In sports medicine, the measures of muscle properties and function can be used to optimize the training load and recovery and possibly to prevent injuries. Despite potential interesting applications of the tonometry, only limited research is available looking at muscle function using tonometry (1)(2)(3)5,9,11,12,14,17,20).…”

“…Korhonen et al (17) showed that the loading force correlated significantly with the muscle tension. Studies have also found that muscle stiffness increased or that the compliance decreased progressively with increasing relative torque production (1)(2)(3)11,14,17,20). An advantage of tonometry is that it enables the assessment of individual muscle or part of muscle contributions to total force production, which is not possible with dynamometry.…”

Association of muscle hardness with muscle tension dynamics: a physiological property

“…Although muscle hardness may be associated with muscle tone or stiVness, the deWnition of these terms has been ambiguous. Muscle tone and stiVness has been deWned as the ratio of change in force to change in length along the muscle's long axis (Alamaki et al 2007;Leonard et al 2004). On the other hand, muscle hardness, which is detectable by palpation, can be simply deWned as the resistance oVered by the muscle against perpendicular pressure (Horikawa et al 1993;Murayama et al 2000Murayama et al , 2005.…”