Reliability of trunk strength measurements with an isokinetic dynamometer in non-specific low back pain patients: A systematic review

Cross-limb transfer during isometric plantar flexion familiarization

This study examined the number of contractions required for an isometric plantar flexion familiarization. Twenty-six males were separated into two independent Groups: Group A: where five contractions were initiated on the dominant limb (right) followed by the contralateral limb; and Group B, initiated by the non-dominant limb (left) followed by the dominant limb. Participants carried out a 5-s maximum voluntary contraction (MVC), with an interpolated twitch administered to the tibial nerve. In Group A, both the dominant and non-dominant limbs required two contractions for familiarization, whereas in Group B, the dominant limb required two contractions, and the non-dominant limb required three (p < 0.05). A strong relationship between MVC and voluntary activation (VA) was observed in Group A for the D (r = 0.91, p < 0.05) and in Group B for the ND limb (r = 0.99, p < 0.05). The results demonstrated evidence of cross-limb transfer from the dominant to the non-dominant limb (p < 0.05). This phenomenon implicates central involvement, substantiated by VA responses that mirror the changes in MVC. Practitioners and researchers should consider the impact of cross-limb transfer during a single familiarization session when assessing strength to avoid overestimation of the gains. Future cross-education/cross-limb transfer studies could investigate the central mechanisms involved during familiarization.

Responsiveness of hand-held dynamometry for measuring changes in trunk muscle strength in people with chronic low back pain

OBJECTIVE

To assess the responsiveness of a hand-held dynamometer (HHD) in evaluating changes in trunk isometric strength in people with chronic low back pain (LBP).

BACKGROUND

Reduced trunk muscle strength has been associated with pain incidence and severity in people with chronic LBP. Trunk muscle strength is an important functional outcome that is measured in clinical practice and research. However, the responsiveness of clinical tools such as HHD for measuring changes in trunk muscle strength remains underexplored.

METHODS

Maximum isometric trunk strength was measured using both a HHD and an isokinetic dynamometer (ID) in 21 participants with chronic LBP both before and after 6 weeks of progressive trunk resistance exercises. Effect sizes (ES) and standardised response mean (SRM) were used to evaluate the internal responsiveness of the HHD measures. External responsiveness was determined by correlating the change scores measured with the HHD with those obtained using the ID.

RESULTS

Following the progressive resistance exercise programme, there was a significant improvement in trunk muscle strength measured with the HHD with moderate to large ES (0.40-0.85) and SRM (0.60- 0.74), indicating moderate to high internal responsiveness. Pearson's correlations revealed a weak correlation between changes in trunk strength measured with the HHD and those measured with the ID (r = 0.22- 0.26), indicating inadequate external responsiveness.

CONCLUSIONS

Although the use of a HHD was shown to have internal responsiveness for detecting changes in trunk muscle strength, the inadequate external responsiveness warrants further investigation. Future research should also explore the responsiveness of HHD in people with chronic LBP with higher pain and disability levels using comparable measurement setups.

A Comparison of Contractile Properties and Acute Muscle Fatigue Response in Adult Females with Non-Specific Chronic Low Back Pain

This study examined the erector spinae contractile properties, trunk isokinetic strength, and differences in acute muscle fatigue response after exercise in young females with and without non-specific chronic low back pain (NSCLBP). This study evaluated participants using tensiomyography and isokinetic trunk strength tests. An independent t-test compared the control group and the NSCLBP group, while a two-way mixed ANOVA analyzed differences in the erector spinae's acute muscle fatigue response before and after exercise within and between groups. The results of the tensiomyography indicated that the NSCLBP group exhibited significantly lower Dm and Vc (p < 0.05) compared to the control group, while Tc showed no significant difference between groups. Significant differences in all variables were observed between the groups in the isokinetic trunk strength test (p < 0.05). Furthermore, the two-way mixed ANOVA revealed significant group main effects in Dm and Vc of the erector spinae (p < 0.05). This study found that non-specific chronic low back pain is linked to a decrease in Dm, Vc, and trunk isokinetic strength in both extensor and flexor muscles. It suggests that future research should further investigate the acute muscle fatigue response in individuals with and without NSCLBP.

Age-Related Differences in the Functional Demand Placed on the Lumbar Spine during Walking in Healthy Older versus Younger Men

Age-related declines in the musculoskeletal system may place additional demands on the lumbar spine during everyday activities such as walking. This study aimed to investigate age-related differences in the functional demand (FD) of walking on the lumbar spine in older and younger adults. A motion analysis system with integrated force plates was used to acquire kinematic and kinetic data on 12 older (67.3 ± 6.0 years) and 12 younger (24.7 ± 3.1 years) healthy men during walking at a self-selected speed along a 10 m walkway. Isokinetic dynamometry was used to acquire the maximal joint moment capacity of the lumbar spine. The FD of the lumbar spine was calculated as the muscle moment during key phases of the gait cycle (GC) relative to the maximum moment capacity of the lumbar spine. The difference in FD between age groups was not significant (p = 0.07) and there were no significant differences between the young group (YG) and older group (OG) for any individual phase in the GC. Despite the lack of statistical significance, the results indicate that a practical difference may exist, as walking was approximately 20% more functionally demanding on the lumbar spine in the OG compared to the YG. Therefore, older adults may employ modified gait strategies to reduce mechanical load whilst walking to fall within the limits of their maximal force-producing capacity in the lumbar spine, which may have implications for injury risk.

Changes in isokinetic trunk muscle strength and endurance after two different restoration programs in people with chronic low back pain: A longitudinal retrospective study

Background

Multidisciplinary functional restoration programs (FRPs) aim to improve pain and function in people with chronic low back pain (CLBP). The intensity and content of FRPs varies; the benefits of one program over another are unclear.

Objective

To assess changes in trunk muscle strength and endurance after an intensive (IFRP) (for people on sick leave for >6 months with high levels of fear-avoidance beliefs about physical activity and work) or semi-intensive (SIFRP) (for people working) FRP in people with CLBP.

Methods

Longitudinal retrospective study from March 2016 to December 2019. Setting: rehabilitation department of a tertiary care center. Trunk flexor and extensor muscle strength (60°.s-1) and endurance (120°.s-1) were measured with the Humac NORM isokinetic dynamometer at pre and post FRP. Change in isokinetic variables (peak torque, total work and flexor/extensor ratio) after each program was assessed with a paired t-test (p < 0.05). Pearson's rho and multiple linear regression assessed associations between changes in isokinetic and clinical variables and demographic characteristics.

Results

125 individuals, 63.2 % female, age 43.5 (10.3) years, were included. Mean low back pain intensity was 49.8 (24.9) and 37.2 (25.8)/100 and mean activity limitation (QBPDS) was 38.8 (16.4) and 32.0 (14.6)/100 in the IFRP and SFRP groups, respectively. Trunk extensor peak torque, flexor total work, extensor total work and flexor/extensor peak ratio improved significantly in both FRPs, p < 0.001. The flexor/extensor total work ratio improved in the IFRP group only, p = 0.003. Trunk extensor endurance increased more in the IFRP than the SIFRP group, the absolute pre-post differences for extensor total work [95%CI] N.m were 611.7 [495.2; 728.3] in the IFRP group and 380.0 [300.8; 459.3] in the SIFRP group. No variables were correlated and none predicted improvement in extensor total work in either group.

Conclusion

This study highlights the short-term independence of clinical and trunk muscle strength and endurance changes.

Using Resistance-Band Tests to Evaluate Trunk Muscle Strength in Chronic Low Back Pain: A Test-Retest Reliability Study

Exercise is a front-line intervention to increase functional capacity and reduce pain and disability in people with low strength levels or disorders. However, there is a lack of validated field-based tests to check the initial status and, more importantly, to control the process and make tailored adjustments in load, intensity, and recovery. We aimed to determine the test-retest reliability of a submaximal, resistance-band test to evaluate the strength of the trunk stability muscles using a portable force sensor in middle-aged adults (48 ± 13 years) with medically diagnosed chronic low back pain and healthy peers (n = 35). Participants completed two submaximal progressive tests of two resistance-band exercises (unilateral row and Pallof press), consisting of 5 s maintained contraction, progressively increasing the load. The test stopped when deviation from the initial position by compensation movements occurred. Trunk muscle strength (CORE muscles) was monitored in real time using a portable force sensor (strain gauge). Results revealed that both tests were highly reliable (intra-class correlation [ICC] > 0.901) and presented low errors and coefficients of variation (CV) in both groups. In particular, people with low back pain had errors of 14-19 N (CV = 9-12%) in the unilateral row test and 13-19 N (CV = 8-12%) in the Pallof press. No discomfort or pain was reported during or after the tests. These two easy-to-use and technology-based tests result in a reliable and objective screening tool to evaluate the strength and trunk stability in middle-aged adults with chronic low back pain, considering an error of measurement < 20 N. This contribution may have an impact on improving the individualization and control of rehabilitation or physical training in people with lumbar injuries or disorders.

Effects of 16-week circuit training on physical fitness parameters, pulmonary function, and quality of life in healthy women

BACKGROUND

Circuit training (CT) is an important type of training that can combine different types of exercises in a single form of training. This study aimed to investigate the effects of 16-week CT on physical fitness parameters, pulmonary function, and quality of life in healthy women.

METHODS

Twenty-nine healthy women (median age: 37.00 [31.50/39.50] years) were included in the study. CT was applied to the participants for a total of 16 weeks. Participants' body composition with the Bioelectrical Impedance Analysis System, knee flexor and extensor muscle strength with the Biodex System-4 Pro, flexibility with the sit-and-reach test, pulmonary function with a spirometer device, and quality of life with Short Form-36 were assessed.

RESULTS

A significant difference was found between the participants' pretest and posttest median and interquartile range values of waist-hip ratio, body mass index, right/left knee flexor/extensor mean peak torque (60°/s,180°/s), right hamstring/quadriceps (H/Q) ratio (60°/s), flexibility, and SF-36 Mental Health Score (P˂0.050). There was no significant difference between the participants' pretest and posttest median and interquartile range values of total body fat, fat percentage, right H/Q ratio (180°/s), left H/Q ratio (60°/s,180°/s), pulmonary function, and Short Form-36 Physical Function Score (P˃0.050).

CONCLUSIONS

CT decreased waist-hip ratio and body mass index, increased knee flexor/extensor strength and flexibility, and improved mental health. The 16-week CT may be an alternative approach to improve physical fitness parameters and mental health without any positive effects on body fat and pulmonary functions in healthy women.

The reliability, variability and minimal detectable change of multiplanar isometric trunk strength testing using a fixed digital dynamometer

Trunk strength plays a vital role in athletic performance, rehabilitation and general health, however, current assessment methods are expensive, non-portable or unreliable. This study aimed to investigate the within- and between-session reliability, variability, standard error of measurement and minimal detectable change (MDC) of trunk strength in the sagittal (flexion and extension) and frontal planes (left and right lateral flexion) using a fixed digital dynamometer. Eighteen participants (ten men and eight women) attended two sessions separated by 7 days. Participants were fitted with a trunk harness which was secured to an immovable base via a digital dynamometer. Three maximal voluntary isometric contractions were completed across four positions (prone, supine, left-side recumbent and right-side recumbent, respectively) on a glute-hamstring raise machine. All positions demonstrated excellent reliability and low variability within session (ICC: 0.95-0.98; CV: 5-7%) and between sessions (ICC: 0.98-0.99; CV: 4-6%), across all positions. The between-session MDC ranged from 8% (prone) to 13% (right-side recumbent), translating to absolute values between 2.9 and 3.2 kg across all positions. Maximal isometric force testing using a fixed digital dynamometer provides reliable measurements of multiplanar trunk strength, providing a practical method for use in clinical practice.

Comprehensive Physical Work Capacity Evaluations for Korean Farmers Assessed in Healthy Volunteers

OBJECTIVE

To establish the lower limits of normative values of the physical work capacity for Korean farmers in healthy working individual.

METHODS

We developed a comprehensive set of physical work capacity evaluation items that encompass common farming tasks. These items include measurements of trunk flexion/extension angles, strength (hand grip, trunk flexion/extension, leg/back lifting, and pushing/pulling), and positional tolerances. We calculated the normative values for the items and defined the normal range in 124 healthy volunteers aged 20-79 years. We calculated the intraclass correlation coefficient (ICC) to validate the test-retest reliability of the measurements protocol.

RESULTS

The normal values for each measurement item were as follows: trunk flexion and extension angle (65.3°±11.6° and 29.6°±6.6°), dominant hand grip strength (32.2±10.5 kgf), trunk flexion and extension strength (288.4±119.0 N and 297.3±129.9 N), leg and back lifting strength (452.9±233.5 N and 349.2±166.7 N), pushing and pulling strength (214.7±75.1 N and 221.7±63.3 N), and positional tolerance time (squat: 76.8±9.0 seconds, front: 73.8±7.7 seconds, twist: 82.2±8.8 seconds, upward: 71.9±11.3 seconds). Regarding test-retest reliability, all strength measurements demonstrated excellent absolute agreement (ICC, 0.91-0.96). However, positional tolerance showed poor-to-moderate absolute agreement (ICC, 0.37-0.58).

CONCLUSION

We conducted measurements of muscle strength and positional tolerance in healthy participants of various ages, focusing on tasks commonly performed by Korean farmers. The outcomes hold significant value as they offer a pertinent instrument for assessing the appropriateness of workers, thereby carrying implications for rehabilitation objectives, legal evaluations, and work capacity assessments within the agricultural domain.

Rehabilitation therapy using the HUBER platform in chronic non-specific low back pain: a randomized controlled trial

BACKGROUND

Non-specific chronic low back pain (NSCLBP) refers to a complex condition that involves structural, biomechanical, cognitive, psychological, social, and lifestyle issues. First-line therapies include physical therapy and exercise, as well as psychological follow-up and pain medication.

AIM

The aim of this study was to assess the impact of a 6-week center-based program using a multi-axis motorized platform (HUBER) connected with force sensors, that allows the patients to execute isometric exercises on the spine flexion-to-extension ratio at 60 and 120°/s, pain, trunk flexibility, and disability.

DESIGN

The design of the study was prospective, active control, parallel-group, assessor-blinded, randomized controlled trial.

SETTING

The setting was outpatients physical therapy clinic.

POPULATION

The population analyzed presented NSCLBP.

METHODS

Seventy individuals with NSCLBP were randomized into 2 intervention arms (1:1 ratio): 1/standard rehabilitation group (STAND) with physiotherapy, balneotherapy and cycloergometer exercises and 2/HUBER rehabilitation group (HUB) with physiotherapy, balneotherapy and HUBER exercises. Both programs lasted 6 weeks, with 4 sessions of 2 hours each per week.

RESULTS

Each group reported statistically significant improvements on the isokinetic spine strength, flexibility of the trunk, lumbar joint mobility, muscular endurance of the trunk and of the lower limbs, pain score and disability (P<0.05). The spine flexion/extension ratio at 60˚/s improved similarly between groups (-22.23 for HUB, and -13.04 for STAND; P=0.178) with a greater effect size in HUB. Only HUB reported a significant improvement in the spine flexion-to-extension ratio at 120˚/s (from 87.3 to 78.6, P=0.012). HUB reported a greater decrease in the Oswestry Disability Index (-16.83) compared to STAND (-12.11), with a statistically significant effect between groups (P=0.036).

CONCLUSIONS

Exercises performed on the HUBER platform added to physiotherapy and balneotherapy are as effective as a standard rehabilitation program with physiotherapy, balneotherapy and cycloergometer exercises to improve isokinetic spine strength, lumbar joint mobility, flexibility and muscular endurance of the trunk and the lower limbs. In addition, exercising with the HUBER platform result in a greater reduction in disability compared to a standard rehabilitation program (clinicalTrials.gov: NCT05437016).

CLINICAL REHABILITATION IMPACT

A variety of intervention techniques, including supervised exercise and manual therapy are now used to manage persistent NSCLBP. The added value of the HUBER device on disability suggests that the platform could be beneficial.