The modified sphygmomanometer—An instrument to measure muscle strength: A validation study

Is the modified aneroid sphygmomanometer a valid instrument to measure isometric quadriceps strength? Three techniques were compared: the cuff method, in which the original cuff and bladder were folded then secured by rubber bands; the bag method, in which the folded bladder was secured in a sewn bag; and a standard method, employing weights. Using a design to control for method and order of measurement, five physiotherapists measured quadriceps muscle strength in five rheumatoid patients. The design features explained 97% of the variation amongst the measurements. Order of observation and the observers had no effect on the measurements. Patients were quite different and methods of measurement were different. The cuff and bag methods obtained higher readings than the weights, and the bag readings were higher than the cuff. Compared to the standard weights, the sphygmomanometer methods were: equally sensitive and reproducible, performed in 16th of the time, independent of gravity and potentially adaptable to 24 different muscle groups.