(11) DETERMINATION OF 1 REPETITION MAXIMUM AND MAXIMAL NEUROMUSCULAR CAPACITIES FOLLOWING A SINGLE-SESSION LOAD-VELOCITY PROTOCOL

Traditional load-velocity profile (LVP) protocols rely on previous assessment of the 1 repetition maximum (1RM) to calculate relative loads. The validity of an absolute load incremental protocol to obtain the LVP and 1RM value has not yet been determined.

Purpose: To determine whether a single-session of absolute incremental loading is valid to obtain both the LVP and 1RM for the back-squat exercise.

Methods: Fifteen strength-trained males (age:23.8±3.4, body mass:76.7±8.3kg, back-squat 1RM/body mass ratio:1.7±0.2) attended three testing sessions: 1RM assessment (baseline) and two LVP protocols for the free-weight, eccentric-concentric parallel back-squat exercise. One LVP protocol was based on incremental relative loads (LVP_rel; 40, 60, 80, 90, 100%1RM) and the other consisted of absolute load increments until 1RM (LVP_abs;initial load set for 20kg, with 2.5-15kg increments, depending on barbell mean concentric velocity (MCV) (Chronojump, Barcelona, Spain). LVPs were modeled using a least-square linear regression. The following maximal neuromuscular capacity (MNC) variables were obtained: L₀ as measure of maximal strength, s as the slope of the LV relationship, V₀ as maximal velocity capacity and A_line as an index of maximal power capacity (A_line=L₀*v₀/2). Paired t tests were used to explore differences for 1RM and velocity at 1RM (v1RM) between baseline vs. LVP_abs and for MNC variables between LVP_rel vs. LVP_abs. The absolute percent error between sessions was also calculated and unilateral t tests were used to test whether it differed from zero. Agreement between 1RM and v1RM measured at baseline and following LVP_abs was analyzed with Bland-Altman plots. The same procedure was applied to assess MNC variables’ agreement between LVP_rel and LVP_abs.

Results: 1RM and v1RM were not significantly different between sessions (p >0.05 for both comparisons). There was a low absolute percent error for 1RM (1.3%), but not for v1RM (12.6%). No differences were found for MNC variables between LVP protocols (p >0.05 all comparisons), and the absolute percent error between protocols ranged from low (L₀=3.4%;V₀=3.9%,A_line=3%) to moderate (s=6.7%). 1RM, v1RM and MNC variables’ mean difference between sessions was on average nearly zero (1RM:-0.5kg; v1RM:-0.002m.s^-1; L₀:-0.55kg; s:0.75kg.m.s^-1; V₀:0.002m.s^-1; A_line=-0.13kg.m.s^-1), and the agreement error exhibited narrow 95% confidence intervals (1RM:1.53kg; v1RM:0.02m.s^-1; L₀:4.76kg; s:6.1kg.m.s^-1; V₀:0.04m.s^-1; A_line=2.56kg.m.s^-1). Analyses of Pearson’s correlation between the absolute difference and mean values for each variable revealed homoscedasticity for all comparisons (R value with p >0.05).

CONCLUSION. Given the lack of mean differences and narrow limits of agreement for 1RM and MNC variables, our data suggests these measurements can be validly obtained following a single session of LVP_abs.
PRACTICAL APPLICATIONS: Without previous knowledge of the individual back squat 1RM, coaches can structure a single-session approach consisting of an absolute load incremental protocol to determine both LVP and direct 1RM assessment for the free-weight back squat.

Acknowledgements: This work was partly supported by the Fundação para a Ciência e Tecnologia (2020.09812.BD)