Isometric Trunk Flexion Research Articles

Trunk muscle strength and back muscle endurance in construction workers with and without low back disorders

The aim of this study was to test the hypothesis that male workers exposed to heavy work and with no lifetime history of a low back disorder (group A) have better trunk muscle strength and back muscle endurance compared to male workers with the same work exposure but with a probable (group B) or definite low back disorder (group C). Group A (n = 42) was clinically negative on physical examination. Group B (n = 75) was clinically negative or uncertain and group C (n = 86) was clinically positive, with current or previous low back disorders occurring in both groups. Group A had a significantly higher mean intraindividual extension/flexion ratio, namely 1.29 versus 1.19, in group C. The mean values for maximum isometric trunk extension and flexion strength did not differ between the groups. The isometric trunk extensor endurance was significantly lower in group C than in both group A and group B.

Evaluation of the physical work load of bricklayers in the steel industry.

A study was made of work conditions suspected of being responsible for a greater prevalence of musculoskeletal disorders among 33 bricklayers. A standardized questionnaire was used to confirm a high 12-month prevalence of 73% for the low back and about 20% for the upper limbs. Physical work load was studied with the use of heart rate recordings and posture analyses. According to the heart rate data, the work load was "moderately heavy" (300 W). A diagnostic analysis identified work postures that could be considered as imposing a heavy strain on the musculoskeletal system. The risk associated with these postures was investigated with biomechanical models. This analysis procedure made possible elaborate ergonomic solutions that reduced the work load in general and the biomechanical constraints in particular.

Strength characteristics of a healthy urban adult population

A random sample of 778 subjects representing ages 25, 35, 45 and 55 years were studied for the amount of habitual physical activity, their anthropometric structure, vertical jumping height, trunk extension and flexion torques and dynamic endurance fitness of trunk extension and flexion. The proportion of subjects who were habitually physically active did not change systematically with age. The highest number of physically inactive subjects was found in men and women in the 35-year age group. The results in all the tests used to assess the strength characteristics were statistically significant when related to sex (P less than 0.001) and in all, except the relative maximal isometric torque of trunk extension, when related to age (P less than 0.001). Everyday physical activity was related to the variation in vertical jumping height (P less than 0.001), as well to the dynamic endurance fitness (P less than 0.001) of trunk extension and flexion. The decline in vertical jumping height and dynamic endurance fitness of trunk extension and flexion fitness was found to start at earlier ages than that of relative maximal isometric trunk extension and flexion torques. Dynamic endurance fitness of trunk flexion showed a more pronounced decline with age than trunk extension fitness.

The role of the abdominal musculature in the elevation of the intra-abdominal pressure during specified tasks

A series of standardized tasks, isometric trunk flexion and extension and maximal Valsalva manoeuvres, were used to evaluate the role of the abdominal musculature in developing an increased intra-abdominal pressure (IAP). Seven male subjects were measured for IAP, myoelectric activity of rectus abdominis (RA), obliquus externus and internus (OE and OI respectively), erector spinae (ES) and isometric trunk torque. IAPs in all experimental conditions were markedly greater than those that occurred while relaxed. In isometric trunk flexion, IAPs were increased with accompanying high levels of activity from the abdominal muscles. In contrast, little activity from the abdominal muscles occurred during isometric trunk extension, although levels of IAP were similar to those found in the isometric flexion condition. With maximal voluntary pressurization (Valsalva manoeuvre) slightly higher levels of IAP than those found in torque conditions were recorded, this pressure being produced with abdominal activities (OE and OI) less than one fourth their recorded maximum. When isometric torque tasks were added to the Valsalva manoeuvre, patterns of muscle activity (RA, OE, OI and ES) were significantly altered. For Valsalva with isometric trunk extension, activity from OE and OI was reduced while IAPs remained fairly constant. These findings indicate that in tasks where an IAP extension moment is warranted, abdominal pressure can be increased without the development of a large counter-moment produced by the dual action of the trunk flexors. Activation of other muscles such as the diaphragm and transversus abdominis is suggested as helping provide control over the level of IAP during controlled trunk tasks.

The Stability of Isometric Trunk Flexion Measurements

The purpose of this study was to determine (a) the number of isometric trunk flexions needed to obtain a stable measure of exertion, (b) the least variable parameter to be used to quantify maximum isometric trunk flexion, and (c) the time interval needed to obtain the least variable measure of maximum isometric flexion. Ten adult males served as subjects. Each subject performed five trials of one maximum isometric trunk flexion. Each trial lasted for 5 s. The results showed (a) only one trial is required to obtain a stable measure of the maximum torque generated during isometric flexion, (b) more than one trial is required to obtain a stable measure of the average torques, (c) maximum torques are more stable measures than average torques, (d) the first second of a 5-s exertion does not yield stable measurements, and (e) individuals adopt different exertion strategies during each trial.

Intra-abdominal pressure and patterns of abdominal muscle activation in isometric trunk flexion and extension

Intra-abdominal pressure and patterns of abdominal muscle activation in isometric trunk flexion and extension

Musculoskeletal capacity of middle-aged women and men in physical, mental and mixed occupations. A 3.5-year follow-up.

The musculoskeletal capacity of 44 women and 39 men, mean age 55.0 +/- 3.4 years, was studied at the beginning and end of a 3.5 year period. The measurements included anthropometrics, maximal isometric trunk flexion and extension strength, maximal isometric hand grip strength and back mobility. According to a job analysis the subjects were divided into three dominating work groups: physical, mental and mixed groups. The results showed significant changes in anthropometrics, maximal isometric muscle strength and in mobility. The body weight and body mass index among women and the body mass index among men increased significantly during the period. The body height and sum of the skinfolds had on the other hand decreased significantly for both women and men. Women showed significant decreases of 9% and 10% (p less than 0.05 and p less than 0.01) in isometric trunk flexion and extension strength, and an increase of 9% in back mobility (p less than 0.05). In mental work, most of the significant changes occurred among women. Men had significant decreases in isometric trunk flexion and extension, 22% and 16% respectively (p less than 0.001) and an increase of 13% in back mobility (p less than 0.001). The men doing physical work had most of the significant changes in musculoskeletal capacity. The results revealed accelerated changes in musculoskeletal capacity in middle-aged employees.

Effects of Pelvic and Lower Extremity Stabilization on Isometric Trunk Extension and Flexion Muscle Strength

The purpose of this study was to evaluate the effect of varying the type of pelvic and lower extremity stabilization on isometric trunk extension and flexion muscle strength measurements. Two pelvic stabilization systems, one consisting of fixation of the anterior superior iliac spines and sacrum (pelvic fixation) and the second, a strap across the anterior superior iliac spines and a posterior pad at the sacrum (pelvic strap) were compared. The lower extremities were or were not strapped at the thigh, calf, and feet. Torque values for the pelvic fixation system were not different from the pelvic strap system with lower extremity stabilization. Torque values were less with no lower extremity stabilization with both pelvic stabilization systems for flexion but not for extension muscle contractions. The use of an extensive pelvic stabilization system did not produce greater isometric force output than the use of a simple pelvic strap. The use of lower extremity stabilization did produce greater isometric flexion force output than the use of no lower extremity stabilization. J Ortho Sports Phys Ther 1987;9(3):111-117.

Normal trunk muscle strength and endurance in women and the effect of exercises and electrical stimulation. Part 1: Normal endurance and trunk muscle strength in 101 women.

The lack of trunk muscle strength and endurance has frequently been cited as a suspected factor in the etiology of low-back pain. Several investigators have suggested that asymptomatic patients have stronger trunk muscles than patients with low-back pain. People who are physically fit appear to have a decreased incidence of low-back pain. Increased trunk muscle endurance also have been observed to decrease the incidence of low-back pain. The objective evaluation of the strength and endurance of trunk musculature may, therefore, be significant. Part 1 of this study was designed to develop a reproducible strength-endurance screening procedure and to establish normal isometric-isokinetic trunk muscle strength and endurance parameters for women. This study showed that isometric trunk flexion varied from 19-109 Nm and trunk extension from 38-168 Nm. Peak values for isokinetic trunk flexion at two speeds (30 degrees per second and 60 degrees per second) varied from 17-191 Nm and isokinetic trunk extension from 14-208 Nm. The average endurance time for trunk extensors tested with the Sorensen test was 196 seconds.

Trunk flexion in healthy children aged 3 to 7 years.

I tested 80 male and 80 female subjects between the ages of 3 and 7 years on two exercises of isometric trunk flexor muscle strength (half-hold hooklying position and supine flexion position) and one exercise of isotonic trunk flexor muscle strength (hooklying sit-ups) to establish normative data for trunk flexor musculature capabilities. Measurements included the length of time the half-hold hooklying and supine flexion positions were maintained and the number of repetitions of sit-ups. I found no significant differences between the sexes in performance of the isometric tests. I did find, however, a significant difference between age groups for half-hold hooklying and supine flexion tests (p less than .0001), indicating that the ability to perform isometric trunk flexion improves with age. Height was another significant variable contributing to test results (p less than .0001). Children were able to perform sit-ups consistently at age 6 years only; the male subjects performed an average of 20 more sit-ups than the female subjects (p less than .04). I discuss in this article the possible contribution of neuromuscular maturation and physical growth to the development of normal trunk flexion. The results may be useful to clinicians to assess abnormal trunk flexion accurately in children aged 3 to 7 years.