Isokinetic lifting simulation: a normative data study

Lifting motion simulation using a hybrid approach

In this study, a hybrid dynamic model for lifting motion simulation is presented. The human body is represented by a two-dimensional (2D) five-segment model. The lifting motions are predicted by solving a nonlinear optimisation problem, the objective function of which is defined based on a minimal-effort performance criterion. In the optimisation procedure, the joint angular velocities are bounded by time-functional constraints that are determined by actual motions. Symmetric lifting motions performed by younger and older adults under varied task conditions were simulated. Comparisons between the simulation results and actual motion data were made for model evaluation. The results showed that the mean and median joint angle errors were less than 10°, which suggests the proposed model is able to accurately simulate 2D lifting motions. The proposed model is also comparable with the existing motion simulation models in terms of the prediction accuracy. Strengths and limitations of this hybrid model are discussed. Practitioner Summary: Human motion simulation is a useful tool in assessing the risks of occupational injuries. Lifting motions are associated with low-back pain. A hybrid model for lifting motion simulation was constructed. The model was able to accurately simulate 2D lifting motions in varied task scenarios for younger and older subjects.

Effects of age and its interaction with task parameters on lifting biomechanics

This study investigated the age-related differences in lifting biomechanics. Eleven younger and 12 older participants were instructed to perform symmetric lifting tasks defined by different combinations of destination heights and load magnitudes. Lifting biomechanics was assessed. It was found that the trunk flexion in the starting posture was 32% lower and the peak trunk extension velocity was 46% lower in older participants compared with those in younger ones, indicating that older adults tended to use safer lifting strategies than did younger adults. Based on these findings, we recommend that physical exercise programmes may be a more effective ergonomic intervention for reducing the risks of low back pain (LBP) in lifting among older workers, compared with instructions of safe lifting strategies. As for younger workers, instructions of safe lifting strategies would be effective in LBP risk reduction.

Isokinetic and isometric muscle strength in a healthy population with special reference to age and gender

AIM

Muscle strength is an excellent indicator of general health when based on reliable measurements. Muscle strength data for a healthy population are rare or non-existent. The aim of the present study was to measure a set of normal values for isometric and isokinetic muscle strength for all the major joint movements of the body and, from these data, to create a basis for comparison of the muscle strength of an individual with the expected value in a normal population.

METHODS

A randomly selected group, aged 20-80 years, from the Copenhagen City Heart Study were studied. The group was subgrouped according to age and gender. Isometric and isokinetic muscle strength was measured in each subject across the main joints in the body. A statistical model was developed that encompassed the three main muscle groups: upper limbs, trunk and lower limbs.

RESULTS

Muscle strength in healthy men decreases in a linear fashion from the age of 25 years down to between 54% and 89% at the age of 75 years, and seems not highly dependent on any other parameter than age. For women, the muscle strength is dependent on weight and is only related to age from around 40 years of age. The decrease in muscle strength from the age around 40 to 75 years is 48-92%. For most muscle groups, men are 1.5-2 times stronger than women, with the oldest men having strength similar to that observed among the youngest women.

CONCLUSION

We developed a model to compare the isometric and isokinetic muscle strength of all the major joint movements of an individual with values for a healthy man or woman at any age in the range of 20-80 years. In all age groups, women have lower muscle strength than men. Men's muscle strength declines with age, while women's muscle strength declines from the age of 41 years.

Correlations of isokinetic and psychophysical back lift and static back extensor endurance tests in men

Isokinetic lift, psychophysical lift, and static back endurance tests are among the most widely used measurements of muscle function for determining risk for, and recovery from, back problems. After determining test repeatability we examined the degree of association between these test measures in 100 men selected to represent a variety of occupations and lifestyles. Isokinetic lifting had low correlations with test results for psychophysical lifting (r = 0.28) and static back endurance (r = 0.24). Static back endurance and psychophysical lift test results were not at all correlated (r = 0.03). RELEVANCE--:Muscle function measurements for back problems are sometimes arbitrarily selected due to health practioners' beliefs and preferences or practical reasons such as the availability of equipment. Yet little is known about the associations of these tests with one another or with anthropometric factors. The data presented in this study document that isokinetic lift, psychophysical lift, and static back endurance tests appear to measure very different aspects of muscle function, and comparing studies using these different test methods should be approached with these low inter-test correlations in mind.

A randomized-control study of active and passive treatments for chronic low back pain following L5 laminectomy

The professional literature contains relatively few randomized-control studies that have assessed the efficacy of physical therapy approaches to the management of patients with chronic low back pain (CLBP). The purposes of this study were: 1) to investigate the effects of physical agents, joint manipulation, low-tech exercise, and high-tech exercise on objective measures of CLBP; 2) to track the length of CLBP relief; and 3) to determine treatment cost-effectiveness. Two-hundred-fifty subjects (68 females, 182 males; ages 34-51 years) with CLBP following an L5 laminectomy were randomly assigned into five separate groups for a treatment period of 8 weeks. Chronic low back pain status was measured by modified-modified Schober, Cybex Liftask, and Oswestry procedures. Results revealed that: 1) only low-tech and high-tech exercise produced significant improvements (p < .05) in CLBP, 2) the mean period of CLBP relief ranged from 1.6 weeks (control) to 91.4 weeks (low-tech exercise), and 3) low-tech exercise was most cost-effective. It was concluded that: 1) low-tech and high-tech exercise were the only effective treatments for CLBP, 2) low-tech exercise produced the longest period of CLBP relief, and 3) low-tech exercise was the most cost-effective form of treatment. Clinically, low-tech exercise may be the treatment method of choice for the effective management of chronic low back pain.

Isometric back strength in different age groups

Normative data on isometric back strength (IBS) are presented. The IBS of both sexes increased with chronological age, peaked at the third decade of life, and gradually declined thereafter. Males were significantly (p less than 0.001) stronger than females in all age groups, the difference ranging between 16 and 56%. A multiple regression equation was derived to predict IBS, as follows: Male IBS (kgf) = -77.71 - 0.91 age (yrs) + 0.67 height (cm) + 1.50 weight (kg) + 0.24 Quetelet index (R2 = 0.78; SE +/- 16.67 kgf) Female IBS (kgf) = -72.42 - 0.39 age (yrs) + 10.65 height (cm) + 0.08 weight (kg) + 1.04 Quetelet index (R2 = 0.62; SE +/- 10.75 kgf).

The reliability and validity of two new tests of maximum lifting capacity

This study investigated the test-retest reliability and validity of the isokinetic and gravity/inertia modes of the Lido Lift (TM) and the Progressive Lifting Capacity II test (PLC II). Maximum lifting capacity tests were performed in the isokinetic and gravity/inertia modes on the Lido Lift and with the PLC II with 29 healthy male subjects. Pearson product-moment correlations were calculated to determine the test-retest reliabilities and to compare PLC II test values with isokinetic and gravity/inertia test values. The correlations for the isokinetic, gravity inertia, and the PLC II werer=.90, .82, and .91, respectively. The correlations between the isokinetic and gravity/inertia tests and the PLC II werer=.64 and .74 during the test andr=.72 and .81 during the retest. The results of this study support the reliability of both Lido Lift (TM) tests and of the PLC II, and the validity of the isokinetic and gravity/inertia tests when compared to the PLC II.

Relative Isoinertial Performance Expressions for the lsostation B-200

Low back internal loads are dependent, in part, upon the weight of the body segments and the lengths of their moment arms. Musculoskeletal performance appears to be influenced by anthropometric characteristics. The purpose of this investigation was to compare dynamic isoinertial performance values to selected individual and permutated anthropometric characteristics. Torque production was assessed during repetitive movements in the axis of trunk flexion/extension in 7 sedentary healthy females. Body fat, stature, and other anthropometric characteristics were measured to predict segmental weights and heights and to express relative performance scores. Pearson correlations ranged from 0.67 to 0.93 between peak torque production and peak torque expressed by both the weight and length of the spine motion segment. These findings appear to be significant because they enable a precise comparison of performance. J Orthop Sports Phys Ther 1990;12(2):60-65.