Use of a Cybex NORM dynamometer to assess muscle function in patients with thoracic cancer

Our plain-English summary of Use of a Cybex NORM dynamometer to assess muscle function in patients with thoracic cancer, by A. Wilcock, M. Maddocks, M. Lewis, et al (BMC Palliative Care, 2008).

The study

• Authors: A. Wilcock, M. Maddocks, M. Lewis, P. Howard, J. Frisby, S. Bell, B. El Khoury, C. Manderson, H. Evans, S. Mockett
• Journal: BMC Palliative Care
• Published: 2008;7:3
• Cited by: 17 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: The cachexia-anorexia syndrome impacts on patients' physical independence and quality of life. New treatments are required and need to be evaluated using acceptable and reliable outcome measures, e.g. the assessment of muscle function. The aims of this study were to: (i) examine the acceptability and reliability of the Cybex NORM dynamometer to assess muscle function in people with non-small cell lung cancer or mesothelioma; (ii) compare muscle function in this group with healthy volunteers and; (iii) explore changes in muscle function over one month.

Methods: The test consisted of 25 repetitions of isokinetic knee flexion and extension at maximal effort while seated on a Cybex NORM dynamometer. Strength and endurance for the quadriceps and hamstrings were assessed as peak torque and total work and an endurance ratio respectively. Thirteen patients and 26 volunteers completed the test on three separate visits. Acceptability was assessed by questionnaire, reliability by intraclass correlation coefficients (ICC) and tests of difference compared outcomes between and within groups.

Results: All subjects found the test acceptable. Peak torque and work done were reliable measures (ICC >0.80), but the endurance ratio was not. Muscle function did not differ significantly between the patient and a matched volunteer group or in either group when repeated after one month.

Conclusion: For patients with non-small cell lung cancer or mesothelioma, the Cybex NORM dynamometer provides an acceptable and reliable method of assessing muscle strength and work done. Muscle function appears to be relatively well preserved in this group and it appears feasible to explore interventions which aim to maintain or even improve this.

In plain English

This study, from Nottingham in the UK, tested whether a leg-exercise machine called the Cybex NORM dynamometer was acceptable and reliable for measuring muscle function in people with non-small cell lung cancer or mesothelioma who were still fairly active and had lost little weight. It did not examine asbestos exposure. Thirteen patients (eight with non-small cell lung cancer, five with mesothelioma) and 26 healthy volunteers completed 25 maximal-effort knee bends and straightenings at each of three visits, held 48 hours and one month apart. All participants found the test acceptable. Peak torque (strength) and total work done were reliable measures, with intraclass correlation coefficients above 0.8. An endurance ratio was not reliable, with values below 0.6. Compared with 13 volunteers matched for age, sex and physical activity, patients tended to produce lower strength and work, but the differences were not statistically significant. Neither group changed significantly over one month. The authors concluded that the machine is acceptable and reliable for measuring strength and work done in this group, and that muscle function appears relatively well preserved. They noted the machine's cost and limited availability.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Prospective study of the acceptability and between-day reliability of a muscle function test, with comparison to matched healthy volunteers and repeat testing after one month
• Who was studied: 16 patients and 28 healthy volunteers were recruited in Nottingham, UK. Patients came from respiratory or oncology outpatient clinics and had an ECOG performance status of 0 or 1. Volunteers came from the staff and volunteers at Hayward House. 13 patients (8 with non-small cell lung cancer, 5 with mesothelioma) and 26 volunteers completed the study. Dates of the study are not given.
• Exposure: No asbestos or other environmental exposure was studied. The test studied was 25 repetitions of isokinetic knee flexion and extension at 180 degrees per second, at maximal effort, on a Cybex NORM dynamometer, repeated on three visits.
• Main results:
  • All patients and volunteers found the test acceptable and completed all tests. Two subjects reported minor discomfort from a strap or the limb stabilizer.
  • In all 39 patients and volunteers combined, peak torque and work done had intraclass correlation coefficients above 0.8. For the quadriceps: peak torque 0.91 (95% CI 0.82 to 0.95) and work 0.84 (0.69 to 0.92). For the hamstrings: peak torque 0.86 (0.75 to 0.93) and work 0.88 (0.77 to 0.94).
  • The endurance ratio was less reliable, with intraclass correlation coefficients below 0.6: 0.56 (95% CI 0.17 to 0.77) for the quadriceps and 0.49 (0.02 to 0.74) for the hamstrings.
  • Compared with 13 matched volunteers, the 13 patients had lower peak torque, did less work and had a higher endurance ratio for both muscle groups, but none of the differences were statistically significant. For example, median quadriceps peak torque was 65 N in patients and 74 N in volunteers, as the article reports it.
  • After one month, no measure changed significantly in either the patient group or the matched volunteer group. The patient group showed a general tendency to get weaker that was not statistically significant.
• The authors' conclusion: The authors concluded that exercise on the Cybex NORM dynamometer is an acceptable and reliable way to measure peak torque and work done in these patients, and that muscle function appears relatively well preserved in this group. In their view, this leaves room for interventions such as exercise training.
• Limitations the authors state:
  • The dynamometer is costly and has limited availability.
  • The form of exercise is unfamiliar to patients, so familiarization with the equipment is needed to achieve maximal performance.
  • Longer studies are needed to identify the usual rate of decline in muscle function in this patient group.
  • The higher endurance ratio in patients may reflect patients not working as hard in the first five repetitions, or the unreliability of the endurance ratio.

Topics

Medical terms in this study, explained in our Lexicon: Cachexia, Quality of Life, Non-Small Cell Lung Cancer, Mesothelioma.

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• Factors influencing exercise performance in thoracic cancer — R. England, M. Maddocks, et al. (2012)
• Occupational therapy needs of patients with thoracic cancer at the time of diagnosis: findings of a dedicated rehabilitation service — R. Bentley, A. Hussain, et al. (2013)
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