COMPARISON OF ISOTONIC ANF ISOMETRIC STRENGTH TESTING
Methods: 10 males and 3 females in the age range of 21 to 32 years were tested for hand grip strength. Their height ranged from 65 to 74 inches and weight ranged from 158 to 260 pounds. The BMI range of the subjects was from 21.9 to 38.3 Hand-grip measurements and bench press tests were perfomed on these subjects. The Average 1 RM hand-grip, Average Handgrip, Arm Strength were estimated for each subject. Combined scores from the isometric tests -Arm plus Shoulder, ∑ of 4 isometric tests, Isometric minus handgrip were also estimated.
Results: Linear regression and the R-squared values to determine the strength of the relationship between the isotonic and the isometric tests were performed from the data obtained. A linear regression equation, y= 1.337x + 83.201 R2 = 0.892 for isotonic versus isometric strength.
Discussion: Greater muscle strength is associated with less mortality due to all causes in men and less mortality due to cancer in men above the age of 60 years (Ruiz JR, 2008). This relation between muscle strength and mortality or cancer holds good even after taking into consideration other factors such as cardiorespiratory fitness and other factors (Ruiz JR, 2008). Accurate measurements of the human muscular system have been the object of study by medical practitioners and rehabilitation professionals for many years. Thus, measures for muscle strength measurement should be accurate and reliable (Cortez PJ, 2011).
Physical activity is usually extremely low in current Western societies as compared to earlier times along with excess food intake leading to an obesity epidemic. This is one of the leading causes of death in the United States, even surpassing smoking as a cause of preventable death (Gielen S, 2010). Diseases that cause an impairment of the cardiovascular system or the pulmonary system can affect peripheral muscle strength (Kröönströma LA, 2014). These are health conditions such as heart attacks and chronic obstructive pulmonary disorders that cause decreased exercise tolerance and reduced peripheral muscle strength (Robles PG, 2014).
Hand-grip tests involve a relatively small group of muscles. Isometric tests measure isometric contractions which are the tension developed when there is no change in the external length of the muscle. Based on the results, it seems that isotonic strength of the upper body can be used to estimate isometric strength of the work-related isometric strength tests. Other factors that should be included are experience of the tester, better devices for measuring muscle strength with better accuracy and reliability such as dynamometers (Topendsports website). Factors such as dominant limb compared to non-dominant limb should also be considered. It is estimated that the dominant limb has 10 percent more strength than the non-dominant limb (Roberts HC, 2011).
Hand grip strength can be used to estimate isotonic and work-related isometric strength. Other factors that improve the use of various estimates from handgrip include consideration of hand size, age, position of elbow and shoulder (Roberts HC, 2011). The factors that influence the accuracy of the measurements and the equations derived from those measurements include the type of meter used for the measurement, whether the dominant hand was used, calibration of the dynamometer and other factors (Roberts HC, 2011). Larger number of participants, warm up time, environmental conditions such as noise, heat and light, age and overall health of participants, potential motivating factors such as challenges can all affect the accuracy and reliability of the results of the strength test results.
REFERENCES:
Ruiz JR, Sui X, Lobelo F, et al, (2008), ‘Association between muscular strength and mortality in men: prospective cohort study’, BMJ, Volume 337
Cortez PJ, I Jose, Tomazini E, Vitor I, Valenti E, Correa J, Valenti E, Carlos de Abreu L (2011), ‘ A new device to measure isometric strength in upper limbs: comparison between dominant and non-dominant limbs’, CLINICS, Volume 66 Number 2,351-354
Gielen S, Schuler G, Adams V, (2010), ‘Cardiovascular Effects of Exercise Training, Molecular Mechanisms’, Circulation, Volume 122, 1221-1238
Kröönströma LA,D, Johansson L, Anna-Klara Zetterström , Dellborgb M, Eriksson P, Cider A, (2014), ‘Muscle function in adults with congenital heart disease’, International Journal of Cardiology, Volume 170, 35-363
Robles PG, Mathur S, Janaudis-Fereira T, Dolmage T, Goldstein RS, Brooks D (2011), ‘Measurement of Peripheral Muscle Strength in Individuals with Chronic Obstructive Pulmonary Disease: A Systematic Review’, Journal of Cardiopulmonary Rehabilitation and Prevention, Volume 31, Number 11–24
Dynamometers, http://www.topendsports.com/testing/tests/handgrip.htm Retrieved from website on Dec 6, 2014
Roberts HC, Denison HJ, Martin HJ, Patel HP, Syddall H, Cooper C and Sayer AA (2011) ‘A review of the measurement of grip strength in clinical and epidemiological studies: towards a standardized approach’, Age Ageing, Volume 40, Number 4): 423-429
- Based on the results, can you use isotonic strength of the upper body to estimate isometric strength of the various components of the work-related isometric strength tests? How much faith can you place in your estimates and what other factors do you think should be included to improve the estimates?
- Based on the results, can you use handgrip strength to estimate isotonic and work-related isometric strength? What other factors could be included to improve the use of the various estimates from handgrip?
- Based on your experience in the isotonic and isometric labs, what factors influenced the accuracy of the measurements and the equations derived from those measurements (e.g.: subject variables (number of subjects, warm-up, motivation, etc.), test equipment (weights, gauges, devices, etc.), environmental conditions (noise in the room, etc.) tester (expertise, etc.)]?
