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Pe ´rez-Castilla, A, Suzovic, D, Domanovic, A, Fernandes, JFT, and Garcı ´a-Ramos, A. Validity of different velocity-based methods and repetitions-to-failure equations for predicting the 1 repetition maximum during 2 upper-body pulling exercises. J Strength Cond Res 35(7): 1800-1808, 2021-This study aimed to compare the accuracy of different velocity-based methods and repetitions-to-failure equations for predicting the 1 repetition maximum (i.e., maximum load that can be lifted once; 1RM) during 2 upper-body pulling exercises. Twentythree healthy subjects (twelve men and eleven women) were tested in 2 sessions during the lat pull-down and seated cable row exercises. Each session consisted of an incremental loading test until reaching the 1RM followed by a set of repetitionsto-failure against the 80% 1RM load. The 1RM was estimated from the individual load-velocity relationships modeled through 4 (;40, 55, 70, and 85% 1RM; multiple-point method) or 2 loads (;40 and 85% 1RM; 2-point method). Mean velocity was recorded with a linear position transducer and a Smartphone application. Therefore, 4 velocity-based methods were used as a result of combining the 2 devices and the 2 methods. Two repetitions-to-failure equations (Mayhew and Wathen) were also used to predict the 1RM from the load and number of repetitions completed. The absolute differences with respect to the actual 1RM were higher for the repetitions-to-failure equations than velocity-based methods during the seated cable row exercise (p = 0.004), but not for the lat pull-down exercise (p = 0.200). The repetitions-to-failure equations significantly underestimated the actual 1RM (p , 0.05; range: 26.65 to 22.14 kg), whereas no systematic differences were observed for the velocity-based methods (range: 21.75 to 1.65 kg). All predicted 1RMs were highly correlated with the actual 1RM (r $ 0.96). The velocity-based methods provide a more accurate estimate of the 1RM than the Mayhew and Wathen repetitions-to-failure equations during the lat pull-down and seated cable row exercises.

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A range of force (F) and velocity (V) data obtained from functional movement tasks (e.g., running, jumping, throwing, lifting, cycling) performed under variety of external loads have typically revealed strong and approximately linear F-V relationships. The regression model parameters reveal the maximum F (F-intercept), V (V-intercept), and power (P) producing capacities of the tested muscles. The aim of the present study was to evaluate the level of agreement between the routinely used "multiple-load model" and a simple "two-load model" based on direct assessment of the F-V relationship from only 2 external loads applied. Twelve participants were tested on the maximum performance vertical jumps, cycling, bench press throws, and bench pull performed against a variety of different loads. All 4 tested tasks revealed both exceptionally strong relationships between the parameters of the 2 models (median R = 0.98) and a lack of meaningful differences between their magnitudes (fixed bias below 3.4%). Therefore, addition of another load to the standard tests of various functional tasks typically conducted under a single set of mechanical conditions could allow for the assessment of the muscle mechanical properties such as the muscle F, V, and P producing capacities.

Although regularly used, the standard strength test (SST) is known to have several shortcomings, such as being based only on sustained maximum forces, and on a relatively large number of trials that expose the tested muscle to rapid fatigue. The purpose of this study was to evaluate alternating consecutive maximum contractions (ACMCs) as a test of the muscle function through its comparison with SST. Twenty-four participants performed both the externally paced isometric ACMC (i.e., series of consecutive maximum force exertions in 2 directions) and SST of the knee extensor and flexor muscle. The derived variables of both tests included the knee extensor and flexor peak forces (PFs) and their maximum rates of development. Movement speed and muscle power output were also assessed through standard maximum performance tests. Both ACMC and SST revealed on average high intratrial (intraclass correlation coefficient [ICC] > 0.80) and moderate-to-high test-retest reliability (ICC > 0.60), and significant (p < 0.05) positive relationships among the PFs and their rates of development of the tested muscles. The variables of both tests also suggested on average moderate correlations with the maximum performance tests. Finally, ACMC variables revealed relatively stable values across a wide range of frequencies including the 'self-selected' one. Although some properties of ACMC could be similar to SST, the important comparative advantages of ACMC could be relatively low and transitional maximum forces exerted, and fewer trials needed for testing 2 antagonistic muscles. Although further research is needed, particularly concerning the external validity and generalizability, we conclude that the ACMC represents a test of muscle function that could be applied either as an alternative or complementary test to SST.

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The aim was to generalize the maximum dynamic output (MDO) hypothesis [i. e., the muscle power output in vertical jumps (VJ) is maximized when loaded with one's own body mass] to variety of VJ. We hypothesized that the subjects' own body (a) would be the optimal load for maximizing the power output (i. e., the no-load condition) and also (b) reveal the maximum benefits of stretch-shortening cycle (SSC). 13 participants performed the maximum squat and various counter-movement jumps when loaded by approximately constant external force ranging from -40% to  + 40% of their body weight (BW). Regarding the first hypothesis, the differences in both the peak and mean power recorded under different load magnitudes revealed maxima close to no-load condition (i. e., from -3% BW to  + 8% BW; R2=0.65-0.96; all P<0.01). Regarding the second hypothesis, the differences in performance between VJ executed with and without SSC also revealed maxima close to no-load conditions (0-2% BW), while the same differences in the power output were observed under relatively low positive loads (14-25% BW; R² = 0.56-0.95; all P<0.01). The findings support the concept that maximal power output occurs close to one's own body mass during VJ with and without SSC, thereby providing additional support to MDO hypothesis.

We tested the hypotheses that the individual strength properties depend on the applied test and the variable extracted, rather than on the muscle group tested. Flexor and extensor muscles acting in the knee and elbow joint were tested in 58 participants. The standard strength test (SST; based on sustained maximum contraction) and alternating consecutive maximum contractions (ACMC; alternating contractions of antagonistic muscles) performed under static conditions were separately applied to provide the maximum force (F) and the rate of force development (RFD) of each tested muscle. The principal component analysis applied on all 16 variables revealed 3 factors that explained 85.5% of the total variance. Contrary to our hypotheses, the individual factors were loaded with the variables recorded from individual muscles, rather than with either the particular variables or tests. The present findings suggest that recording both F and RFD in routine strength testing procedures could be redundant since they may assess the same strength property of the tested muscle. In addition, ACMC may be a feasible alternative to SST since it could assess the same strength properties from two antagonist muscles through a single trial, while being based on relatively low and transient forces.