Detecção do limiar de lactato salivar e da variabilidade da freqüência cardíaca em exercício resistido: comparação entre métodos.
Resumo
Important researches had shown the benefits of resistance training programs
for rehabilitation as well as prophylaxis of physical incapacity. However few studies had
investigated the responses of the intermediate metabolism during the execution of resistance
exercises if carried through steady state or during incremental tests. The purpose of this study
was to investigate the viability of the use of non-invasive methods as trustworthy indicators in
the analysis of the aerobic-anaerobic transition and to compare the physiological responses
between male and female, submitted to discontinuous incremental test of resistance exercise
for lower limb. Eighteen subjects volunteered to participate and provided a written consent (9
males, 24 ± 3 years, 176 ± 5 cm, 72 ± 10 kg and 9 females, 23 ± 2 years, 165 ± 6 cm, 59 ± 10
Kg) in two sessions, distinct days, of counterweighted isoinertial Leg Press 45º machine (LP),
being the 1st session performed to identify the 1 repetition maximum load (1RM) and the 2nd
to accomplish the discontinuous incremental test of the type step in LP (DIT). The loading
gradual scheme was determined in relation to the percentage of 1RM (%1RM). Subjects were
required to perform 20 ± 2 repetitions with a 2 minutes interval between each set when loads
were changed and collection of blood and salivary samples were collected. The blood lactate
concentration ([La-]) had been used as gold standard for the respective comparisons
between the methods. As non-invasive methods the salivary lactate concentrations ([SL]) and
index SD1 of the heart rate variability (HRV) were used, gotten by Poincaré Plotting (PP).
The thresholds identified by [La-] and [SL] (LT and SLT, respectively) had been determined
by Mader and Heck Method (1986). The threshold identified by index SD1 (SD1T) was
determined by Tullpo et al. (1998) criterion. The criterion level for statistical significance was
set at an alpha level of p< 0,05. Statistical differences had not been found in the comparisons
between genders in each step of the DIT for the three variables studied. The thresholds when
expressed in kg revealed significant differences between genders but not intra genders. When
expressed in %1RM the thresholds had been placed in the average enter 29-40% and had not
evidenced significant differences between the thresholds in the conditions intra genders and
between genders. Correlations of 0.89 and 0.78 had been evidenced between the LT and SLT
and SD1T, respectively. The variability of both non-invasive variables was shown inside of
the limits of agreement evidenced by the analyses of Bland-Altman. Thus it is possible to
conclude that as much the SL as index SD1 of HRV responses of similar form to the blood
lactate. This allows the detention of the thresholds of lactate salivary and heart rate variability,
independently of the gender. In this way, as much the SL as index SD1 of the HRV presents
great potential as possible non invasive markers of effort intensity, that they can be used in the
lapsing and the control of the load of work in the resistance exercises. Moreover, the
differences in the metabolic responses between the genders, evidenced in the intensities of
effort above of the threshold, must be considered in the lapsing of the resistance training.