Use and Misuse of the Tape-Measure as a Means of Assessing Muscle Strength and Power

Abstract

The tape-measure is frequently used by the medical profession to assess muscle function following injury. It is assumed that increasing limb girth is reflected by increasing muscle power and strength; but this assumption is empirical and may not in practice be justified. The relationship between thigh circumference and muscle strength and power, measured as the torque produced on an isokinetic dynamometer, was assessed in 64 subjects--24 non-injured sportsmen and 40 injured sportsmen. The correlation between the torque produced at the knee by the knee extensors and flexors and the thigh circumference at three levels was not significant in either group. Comparison of the injured with the non-injured limb also failed to show any correlation. By contrast, in eight subjects, repeated measurements over a six to eight month period showed a significant relationship between change in thigh circumference and change in quadriceps power. It is concluded that a single measurement of circumference at the same point in both thighs of a subject with unilateral injury should not be used as an assessment of muscle function. Serial measurements, however, at the 4 and 10 cm levels may be of value as an index of quadriceps power. Reasons for this are discussed.

Measurement of thigh muscle size using tape or ultrasound is a poor indicator of thigh muscle strength

“…Muscle strength is best estimated using isokinetic dynamometry [22]. However the significant cost of this equipment, and the fact that many subjects may not be able to perform such demanding testing due to pain, limits its use in clinical practice [17,22,38]. As a result, many clinicians use measurement of muscle size as an indirect indicator of muscle strength [17,35,51].…”

“…However the significant cost of this equipment, and the fact that many subjects may not be able to perform such demanding testing due to pain, limits its use in clinical practice [17,22,38]. As a result, many clinicians use measurement of muscle size as an indirect indicator of muscle strength [17,35,51]. This is justified on the basis that some studies have shown that subjects with reduced muscle strength also display reduced muscle size [15,21,34,48,55].…”

“…This is justified on the basis that some studies have shown that subjects with reduced muscle strength also display reduced muscle size [15,21,34,48,55]. In addition, increased muscle size has been reported along with increased muscle strength in subjects undergoing strengthening programmes [1,2,17,61,64].…”

“…The simplest, and most commonly used, method of estimating muscle size in clinical practice is tape measurement [17,29]. However, it's reliability and usefulness as an indicator of muscle strength is debatable [3,17,29,31,38,39,60] More sophisticated equipment such as computerised tomography (CT), ultrasound (US), dual energy X-ray absorptiometry (DEXA) and magnetic resonance imaging (MRI) scanning have also been used to examine muscle size and function [26,37,50].…”

Utilização do esfigmomanômetro na avaliação da força dos músculos extensores e flexores da articulação do joelho em militares

“…Thus, it has become priority for physical therapists to perform evaluations that enable prophylactic actions as well as the evolutive treatment of the articular lesions. However, there are controversies regarding to the application and validity of the methods employed, once the perimeter asymmetry does not necessarily indicate strength asymmetry (1,(4)(5)(6)(7)(8) , the manual muscular test presents a reliability of only 60-65% (2,6,9,10) , the portable dynamometer is not yet regularly manufactured in Brazil and presents different readings according to the manufacturer (3) and the high-reliability isokinetic dynamometer has as primary limiting factor its high cost and the necessity of adequate physical space (11) (board 2).…”