P. Ibacache1, C. Andaur1, M. Capdeville1, C. Sepúlveda1, J. Sovino-Parra1, M. Cano-Cappellacci2
1Universidad Andrés Bello, Faculty of Rehabilitation Sciences, Viña del Mar, Chile, 2Universidad de Chile, Physical Therapy Department, Santiago de Chile, Chile

Background: Muscle quality (MQ) describes physiological functional capacity of muscle tissue, and it is frequently expressed as the muscle strength or muscle power per unit of muscle mass (MM) ratios. To assess MQ there are different methodologies, such as MRI, CTscan, DXA, bioelectrical impedance analysis, and ultrasound involving excessive cost and difficulty of access.
The muscle quality index (MQI) was proposed as a measure to quantify age-related alterations in muscle function (Takai, 2009) and it has been used to assess changes after physical training. The MQI quantifies lower-extremity muscle function using anthropometric parameters and the timed sit-to-stand 10 times test. The MQI has been shown to be a predictor of mortality and it is strongly correlated to the cross-sectional area of the knee extensors and muscle strength of the knee extensors in older adults. Furthermore, it is known that the muscle strength is an indicator of health and life expectancy. However, there is no evidence if MQI can be a useful to assess the muscle strength of knee extensors and skeletal MM in young healthy individuals.
Reference: Takai et al. (2009) doi:10.2114/jpa2.28.123

Purpose: To determine the relationship of the MQI with the muscle strength of knee extensors and total-body skeletal MM in young healthy individuals.

Methods: 27 participants, with a mean age of 22.3±2.2 years old (15 men) were evaluated. The subjects were instructed to stand up from a sitting position and then sit down, 10 times as fast as they can. The MQI was determined using the equation proposed by Takai (2009), using height of the chair, leg length, body mass, time to perform 10 times chair rising and gravitational constant. Body composition was estimated through bioelectrical impedance analysis with InBody S10 (InBody Co, Korea).
Isometric quadriceps muscle strength was assessed with the subjects seated with the hip angle fixed at 100° and knee angle set at 90° of flexion in a quadriceps chair and were stimulated verbally to produce their maximal force for five seconds. A padded cuff (above the ankle malleolus) was attached to the load-cell FMON-1 (artOficio, Chile).
Pearson test was used to assess correlation between MQI and the muscle strength of knee extensors and skeletal MM. Data was analysed using SPSS 24.0 software. This research was approved by the institutional ethics committee (A82-2018).

Results: The muscle strength of knee extensors was 173±65 N, skeletal MM was 28.9±7.0 kg and MQI was 232±92 W. A correlation between MQI and the muscle strength of knee extensors (R=0.732, p<0.001), and between MQI and skeletal MM (R=0.784, p<0.001) were found.

Conclusion(s): MQI reflects accurately the muscle strength of knee extensors and total-body skeletal MM in young individuals. We suggest additional research involving larger samples sizes, as well as to study the usefulness of MQI in youth with obesity and/or metabolic diseases.

Implications: MQI appears to be a relevant clinical method since is useful low-cost field test to estimate muscle strength of knee extensors and total body skeletal MM using only anthropometric measurements, a chair and a chronometer.

Funding, acknowledgements: There was no external funding to finance this research.

Keywords: Muscle strength, Functional test, Muscle mass

Topic: Non-communicable diseases (NCDs) & risk factors

Did this work require ethics approval? Yes
Institution: Universidad Andrés Bello, Chile
Committee: Research Ethics Committee of the Faculty of Rehabilitation Sciences
Ethics number: A82-2018

All authors, affiliations and abstracts have been published as submitted.

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