ABSTRACT
The time-constant of postexercise heart rate recovery (HRRτ ) obtained by fitting heart rate decay curve by a first-order exponential fitting has being used to assess cardiac autonomic recovery after endurance exercise. The feasibility of this model was not tested after resistance exercise (RE). The aim of this study was to test the goodness of fit of the first-order exponential decay model to fit heart rate recovery (HRR) after RE. Ten healthy subjects participated in the study. The experimental sessions occurred in two separated days and consisted of performance of 1 set of 10 repetitions at 50% or 80% of the load achieved on the one-repetition maximum test [low-intensity (LI) and high-intensity (HI) sessions, respectively]. Heart rate (HR) was continuously registered before and during exercise and also for 10 min of recovery. A monoexponential equation was used to fit the HRR curve during the postexercise period using different time windows (i.e. 30, 60, 90, 600 s). For each time window, (i) HRRτ was calculated and (ii) variation of HR explained by the model (R(2) goodness of fit index) was assessed. The HRRτ showed stabilization from 360 and 420 s on LI and HI, respectively. Acceptable R(2) values were observed from the 360 s on LI (R(2) > 0.65) and at all tested time windows on HI (R(2) > 0.75). In conclusion, this study showed that using a minimum length of monitoring (~420 s) HRR after RE can be adequately modelled by a first-order exponential fitting.
Subject(s)
Autonomic Nervous System/physiology , Exercise/physiology , Heart Rate/physiology , Models, Cardiovascular , Recovery of Function/physiology , Resistance Training/methods , Computer Simulation , Humans , Male , Reproducibility of Results , Sensitivity and Specificity , Young AdultABSTRACT
Physical exercise elicits an increase in heart rate (HR), blood pressure (BP) and, consequently, in the rate-pressure product (RPP). Recovery of HR immediately after exercise indicates cardiovascular health. Blood pressure also decreases after exercise, occasionally reaching values lower than pre-exercise levels (postexercise hypotension). Studies have shown a positive effect of water intake on HR recovery after exercise. However, little is known about the effect of water intake on postexercise BP and RPP responses. The objective of this study was to evaluate the effects of water intake on postexercise cardiac work assessed by HR, BP and RPP. Fourteen healthy volunteers (22 ± 1.4 years) participated in the study. The experimental session consisted of HR, systolic (SBP) and diastolic BP (DBP) recording at rest, followed by submaximal exercise on a cycle ergometer. Next, the subjects consumed water and the cardiovascular variables were recorded during recovery. In addition, a control session without postexercise water intake was performed. The RPP was calculated from the product of HR and SBP. Water intake prevented a postexercise hypotensive effect on DBP, but accelerated postexercise HR and RPP reduction during recovery when compared to the control session. It was concluded that water intake is an effective strategy to reduce postexercise cardiac work.
O exercício físico promove a elevação da frequência cardíaca (FC), pressão arterial (PA) e, por consequência, do duplo produto (DP). Imediatamente após o término do exercício, há a recuperação da FC; resposta que indica boa saúde cardiovascular. A PA também apresenta queda pós-exercício, atingindo, eventualmente, valores abaixo do repouso (hipotensão pós-exercício; HPE). Estudos têm demonstrado efeito positivo da ingestão hídrica (IH) sobre a recuperação da FC pós-exercício. Pouco se sabe a respeito do efeito dessa estratégia sobre o comportamento da PA e do DP nesse período. O objetivo do estudo foi investigar o efeito da IH sobre o trabalho cardiovascular pós-exercício, por meio da avaliação da FC, PA e DP. Quatorze voluntários saudáveis (22 ± 1,4 anos) participaram desse estudo. A sessão experimental constou do registro da FC e PA sistólica (PAS) e diastólica (PAD) de repouso, seguido de exercício físico submáximo em cicloergômetro. Posteriormente, realizou-se a IH e registro das variáveis cardiovasculares na recuperação. Adicionalmente, realizou-se uma sessão controle, excluindo-se a IH pós-exercício. O DP foi calculado a partir do produto da FC pela PAS. A IH impediu a ocorrência de HPE na PAD, porém acelerou a redução da FC e do DP, no período da recuperação pós-exercício, quando comparada à sessão controle. Pode-se concluir que a IH é uma estratégia eficiente na redução do trabalho cardiovascular pós-exercício.
