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Comparative Study
. 2018 Oct 11;51(11):e7837.
doi: 10.1590/1414-431X20187837.

Cardiorespiratory and metabolic determinants during moderate and high resistance exercise intensities until exhaustion using dynamic leg press: comparison with critical load

V M Arakelian  1   2   3 , C L Goulart  2 , R G Mendes  2 , F C Caruso  2 , V Baldissera  3 , R Arena  4 , A Borghi-Silva  1   2
Affiliations
Comparative Study

Cardiorespiratory and metabolic determinants during moderate and high resistance exercise intensities until exhaustion using dynamic leg press: comparison with critical load

V M Arakelian et al. Braz J Med Biol Res. .

Abstract

The objective of this study was to assess cardiovascular, respiratory, and metabolic responses during a commonly used dynamic leg press resistance exercise until exhaustion (TEx) at different intensities and compare with critical load (CL). This was a prospective, cross-sectional, controlled, and crossover study. Twelve healthy young men (23±2.5 years old) participated. The subjects carried out three bouts of resistance exercise in different percentages of 1 repetition maximum (60, 75, and 90% 1RM) until TEx. CL was obtained by means of hyperbolic model and linearization of the load-duration function. During all bout intensities, oxygen uptake (VO2), carbon dioxide production (VCO2), ventilation (VE), and respiratory exchange ratio (RER) were obtained. Variations (peak-rest=Δ) were corrected by TEx. In addition, systolic and diastolic blood pressure (SBP and DBP), blood lactate concentration [La-] and Borg scores were obtained at the peak and corrected to TEx. CL induced greater TEx as well as number of repetitions when compared to all intensities (P<0.001). During CL, Borg/TEx, ΔSBP/TEx, ΔDBP/TEx, and [La-] were significantly lower compared with 90% load (P<0.0001). In addition, VO2, VCO2, VE, and RER were higher during CL when compared to 90 or 75%. TEx was significantly correlated with VO2 on CL (r=0.73, P<0.05). These findings support the theory that CL constitutes the intensity that can be maintained for a very long time, provoking greater metabolic and ventilatory demand and lower cardiovascular and fatigue symptoms during resistance exercise.

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Figures

Figure 1.
Figure 1.. Flowchart of the study. RM: repetition maximum; REC: recovery; CL: critical load; LP: Leg press; TEx: time to exhaustion; HR: heart rate; [La-]: lactate.
Figure 2.
Figure 2.. The load-time relationship in response to three progressive resistance exercise tests for all subjects. A, Linearized response as a function of percentage peak load. B, A hyperbolic relationship was found in all subjects. The asymptote represents the critical load. RM: repetition maximum; TEx: time to exhaustion
Figure 3.
Figure 3.. A, Time until exhaustion (TEx) and B, number of repetitions performed in the four intensities during resistance exercise. CL: critical load. Data are reported as means±SD. ε,µ,αP<0.05 compared to CL (one-way ANOVA).
Figure 4.
Figure 4.. Peak Borg scale corrected to time to exhaustion (TEx) (A), variation of systolic blood pressure (ΔSBP) corrected to TEx (B), variation of diastolic blood pressure (ΔDBP) corrected to TEx (C), and lactate ([La-]) corrected to TEx (D) responses at different intensities as well as on critical load (CL). Data are reported means±SD. SBP. αP<0.05 compared to CL; *P<0.05 compared to 60%; #P<0.05 compared 75% (ANOVA).
Figure 5.
Figure 5.. A, Minute ventilation variability (ΔVE), B, oxygen uptake variability (ΔVO2), C, carbon dioxide production variability (ΔVCO2), and D, respiratory exchange ratio variability (ΔRER) corrected to time to exhaustion (TEx) at different intensities as well as on critical load (CL). Data are reported means±SD. αP<0.05 compared to CL; *P<0.05 compared to 60%; #P<0.05 compared to 75%; µP<0.05 compared to CL (ANOVA).
Figure 6.
Figure 6.. Pearson correlation between fatigue time and oxygen uptake (VO2) during critical load.
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