Strength is one of the human basic motor skills, and it is known that the strength highly influences the success in almost all sports disciplines, as well as the success of performance of many daily activities. However, the body's full strength test, according to the author's knowledge, has not yet been developed and validated. The aim of this study was the construction and validation of a new measuring instrument for the assessment of the muscular strength of the entire human body. The reliability, validity and discriminativeness of a new measuring instrument was analyzed which was performed on a specially modified rowing ergometer type Concept II. The sample of examinees (n = 87) was divided into three groups of male and three groups of female examinees, who differed primarily on the level of body activity (low active - active - athletes). All examinees were tested on anthropometric measures, a standard strength test (CMJ), and a newly-constructed strength test on a rowing ergometer that was performed at three levels of load (minimum - medium - maximum). The coefficient of variation (CV) and interclass coefficient of correlation (ICC) indicate the high reliability of a newly-constructed test at all three load levels (CV: 2.6% to 6.5%, ICC: 0.87-0.98). The sensitivity of the test was analyzed through the distribution of results and calculation of Kolmogorov-Smirnov's test of normality. Discrimination of the test was determined by distinguishing groups based on activity. In all three groups of examinees, for all three load levels, good sensitivity of the test was determined, and no distribution of results was significantly different from theoretically normal for the analyzed sample size.Validity was determined by calculating the Pearson coefficient of correlation between the results of the newly-constructed test and standard strength test (CMJ). In the low-activated examinees CMJ and values obtained on a rowing ergometer were r = 0.72 (minimum resistance), r = 0.74 (medium resistance) and r = 0.76 (maximum resistance). The group of physically active subjects had correlation values r = 0.70 (minimum resistance), r = 0.72 (medium resistance) r = 0.72 (maximum resistance), while the highest correlation values were observed in a group of athletes, r = 0.76 (minimum resistance), r = 0.76 (medium resistance) r = 0.78 (maximum resistance). It can be discussed about very large correlations between the measures analyzed in all three groups of examinees which means that the competitive validity of the test is high. This is one of the first studies that has offered and tested the concept of testing the strength of the whole body using the rowing ergometer, i.e. the concept of measuring the strength of the entire body, and the results obtained give new guidelines in the research of power issues as well as in the construction of measuring instruments in kinesiology in general.