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Experimental study in rat metatarsals to determine whether callus vascularity is an indicator of the mechanical strength of healing fractures
Abstracts
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 101women 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 strengthendurance 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 19-109Nm and trunk extension from 38-168 Nm. Peak values for isokinetic trunk flexion at two speeds (30” per second and 60” per second) varied from 17-191 Nm and isokinetic trunk extension from 14-208Nm. The average endurance time for trunk extensors tested with the Sorensen test was 196 seconds. Nordin M. Kahanovitz N, Verderame R, Parnianpour M, Yabut S. Viola K, Greenidge N, Mulvihill M. Spine 1987; 12: 105-l 1
Normal trunk muscle strength and endurance in women and the effect of exercises and electrical stimulation. Part 2: Comparative analysis of electrical stimulation and exercises to increase trunk muscle strength and endurance Several studies have shown positive correlations between muscle strength, flexibility, and the frequency of low-back pain. Weak trunk musculature and decreased endurance have thereby come to be identified as significant risk factors in the development of occupational back problems. Because it is widely accepted that exercise plays an important role in the conservative treatment and prevention of low-back pain, the goals of most rehabilitative programs involves improving the strength and endurance of the low-back pain patient. Whereas electrical stimulation has been shown to increase the muscle strength of the lower extremities, this effect has not been demonstrated for the trunk muscles. Part 2 is a prospective controlled study designed to document and to compare objectively the effects of electrical stimulation and exercise on trunk muscle strength. A total of 117 healthy women were divided randomly into four groups. Two groups received electrical stimulation with electrical parameters, one group received exercises, and one group acted as a control group. The results showed that low-frequency electrical stimulation and exercises significantly (Pc.05) increased isokinetic back-muscle strength compared to the control and medium-high-frequency electrical stimulation groups. Both types of electrical stimulation, however, significantly increased (P<.O5) the endurance in the back muscles compared with the control and the exercise groups. The study showed that electrical stimulation may be a valuable treatment in the early care of low-back pain patients in maintaining and increasing strength and endurance of back muscles when a more active exercise program is too painful to perform. Kahanovitz N. Nordin M, Verderame R. Yabut S. Parnianpour M. Viola K, Mulvihill M. Spine 1987: 12:112-8
235
Experimental study in rat metatarsals to determine whether callus vascularity is an indicator of the mechanical strength of healing fractures Changes in the mechanical properties and percentage area of blood vessels of of healing fracture callus were followed using rat metatarsals. By 24 weeks after fracture the mean ultimate tensile stress and elastic modulus were still less than half that of the contralateral unfractured bone. whereas the mean torsional modulus had almost reached that of the unfractured bone. The percentage area of blood vessels declined from tive days post-fracture and showed no changes which coincided with the increases in mechanical strength or moduli. We conclude that studies of vascnlarity would not justify a prediction of the strength of a healing fracture. Powell ES. Lake DNW. Matthews JG. Lawford PV. Duckworth T. Black MM. J Biomed Eng 1987: 9: 239-56
ERGONOMICS
Relation between overhead work and complaints of pear and apple orchard workers The relation between working posture in overhead work and the complaints of farmers cultivating pears and apples were investigated by comparing pear work with apple work. The same 20 male and 28 female orchard workers were questioned about complaints associated with thinning out pears and bagging them, and bagging apples. The angle of forward flexion in the shoulder and neck extension was also measured in each job. The prevalence of tiredness, stiffness and pain in the neck. shoulders and arms was significantly higher in thinning out pears and bagging them than in bagging apples. Dizziness and tinnitus among female workers was more frequent in thinning pears. The posture of raising arms and bending the head backwards was higher in thinning and bagging pears. These results suggest that the working postures of elevated arms and backward head bending can cause symptoms in the neck. shoulders and arms. In some cases. they may also lead to symptoms of vertebral artery insufficiency. Sakakibara Kobayashi
H. Miyao M, Kondo T, Yamada F. Ergonomics 1987; 30: X05-15
S. Nakagawa
T,
Power hand tool vibration effects on grip exertions Operation of vibrating power hand tools can result in excessive grip force, which may increase the risk of cumulative trauma disorders in the upper extremities. An experiment was performed to study grip force exerted by 14 subjects operating a simulated hand tool vibrating at Y8 m/s’ and 49 m/s* acceleration magnitudes, at 40 Hz and 160 Hz frequencies, with vibration delivered in three orthogonal directions, and with 1.5 kg and 3.0 kg load weights. Average grip force increased from 25.3 N without vibration to 32. I N (27%) for vibration at 40 Hz, and to 27.1 N (7%) for vibration at 160 Hz. Average grip force also increased from 27.4 N at 9.8 m/s* acceleration to 31.8 N (16%) at 49 m/s’. Significant interactions between accelerationxfrequency, and frequencyxdirection were also found. The largest average grip force increase was from 25.3 N without vibration to 35.8 N (42%) for 40 Hz and 49 m/s’ vibration. The magnitude of this increase was of the same order as for a two-fold increase in load weight, where average grip force increased
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 101women 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 strengthendurance 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 19-109Nm and trunk extension from 38-168 Nm. Peak values for isokinetic trunk flexion at two speeds (30” per second and 60” per second) varied from 17-191 Nm and isokinetic trunk extension from 14-208Nm. The average endurance time for trunk extensors tested with the Sorensen test was 196 seconds. Nordin M. Kahanovitz N, Verderame R, Parnianpour M, Yabut S. Viola K, Greenidge N, Mulvihill M. Spine 1987; 12: 105-l 1
Normal trunk muscle strength and endurance in women and the effect of exercises and electrical stimulation. Part 2: Comparative analysis of electrical stimulation and exercises to increase trunk muscle strength and endurance Several studies have shown positive correlations between muscle strength, flexibility, and the frequency of low-back pain. Weak trunk musculature and decreased endurance have thereby come to be identified as significant risk factors in the development of occupational back problems. Because it is widely accepted that exercise plays an important role in the conservative treatment and prevention of low-back pain, the goals of most rehabilitative programs involves improving the strength and endurance of the low-back pain patient. Whereas electrical stimulation has been shown to increase the muscle strength of the lower extremities, this effect has not been demonstrated for the trunk muscles. Part 2 is a prospective controlled study designed to document and to compare objectively the effects of electrical stimulation and exercise on trunk muscle strength. A total of 117 healthy women were divided randomly into four groups. Two groups received electrical stimulation with electrical parameters, one group received exercises, and one group acted as a control group. The results showed that low-frequency electrical stimulation and exercises significantly (Pc.05) increased isokinetic back-muscle strength compared to the control and medium-high-frequency electrical stimulation groups. Both types of electrical stimulation, however, significantly increased (P<.O5) the endurance in the back muscles compared with the control and the exercise groups. The study showed that electrical stimulation may be a valuable treatment in the early care of low-back pain patients in maintaining and increasing strength and endurance of back muscles when a more active exercise program is too painful to perform. Kahanovitz N. Nordin M, Verderame R. Yabut S. Parnianpour M. Viola K, Mulvihill M. Spine 1987: 12:112-8
235
Experimental study in rat metatarsals to determine whether callus vascularity is an indicator of the mechanical strength of healing fractures Changes in the mechanical properties and percentage area of blood vessels of of healing fracture callus were followed using rat metatarsals. By 24 weeks after fracture the mean ultimate tensile stress and elastic modulus were still less than half that of the contralateral unfractured bone. whereas the mean torsional modulus had almost reached that of the unfractured bone. The percentage area of blood vessels declined from tive days post-fracture and showed no changes which coincided with the increases in mechanical strength or moduli. We conclude that studies of vascnlarity would not justify a prediction of the strength of a healing fracture. Powell ES. Lake DNW. Matthews JG. Lawford PV. Duckworth T. Black MM. J Biomed Eng 1987: 9: 239-56
ERGONOMICS
Relation between overhead work and complaints of pear and apple orchard workers The relation between working posture in overhead work and the complaints of farmers cultivating pears and apples were investigated by comparing pear work with apple work. The same 20 male and 28 female orchard workers were questioned about complaints associated with thinning out pears and bagging them, and bagging apples. The angle of forward flexion in the shoulder and neck extension was also measured in each job. The prevalence of tiredness, stiffness and pain in the neck. shoulders and arms was significantly higher in thinning out pears and bagging them than in bagging apples. Dizziness and tinnitus among female workers was more frequent in thinning pears. The posture of raising arms and bending the head backwards was higher in thinning and bagging pears. These results suggest that the working postures of elevated arms and backward head bending can cause symptoms in the neck. shoulders and arms. In some cases. they may also lead to symptoms of vertebral artery insufficiency. Sakakibara Kobayashi
H. Miyao M, Kondo T, Yamada F. Ergonomics 1987; 30: X05-15
S. Nakagawa
T,
Power hand tool vibration effects on grip exertions Operation of vibrating power hand tools can result in excessive grip force, which may increase the risk of cumulative trauma disorders in the upper extremities. An experiment was performed to study grip force exerted by 14 subjects operating a simulated hand tool vibrating at Y8 m/s’ and 49 m/s* acceleration magnitudes, at 40 Hz and 160 Hz frequencies, with vibration delivered in three orthogonal directions, and with 1.5 kg and 3.0 kg load weights. Average grip force increased from 25.3 N without vibration to 32. I N (27%) for vibration at 40 Hz, and to 27.1 N (7%) for vibration at 160 Hz. Average grip force also increased from 27.4 N at 9.8 m/s* acceleration to 31.8 N (16%) at 49 m/s’. Significant interactions between accelerationxfrequency, and frequencyxdirection were also found. The largest average grip force increase was from 25.3 N without vibration to 35.8 N (42%) for 40 Hz and 49 m/s’ vibration. The magnitude of this increase was of the same order as for a two-fold increase in load weight, where average grip force increased