Effect of a lactate‐guided conditioning program on heart rate variability obtained using 24-Holter electrocardiography in Beagle dogs

Abstract

The dogs' responses to training exercise are seldom monitored using physiological variables, and cardiac autonomic regulation (CAR) is a relevant determinant of endurance-training adaptation. There are studies in the literature establishing that regular exercise could interfere with CAR in dogs, measured by heart rate and vagal-derived indexes of heart-ratevariability (HRV). However, few studies were found using a prescribed training program based on the lactate threshold (LT) to determine HRV by a 24-h Holter analysis. The purpose of this study was to test whether an endurance-training program (ETP) guided individually by LT raises time-domain measures of HRV in healthy Beagle dogs. Twenty dogs were assigned to two groups: control (C) and trained (T). The dogs from group T underwent an incremental exercise test (IET) to determine their LT. Both LT and velocity corresponding to the LT (VLT) was determined by visual inspection. T group performed an eight-week endurance-training program consisting of treadmill runs set to 70-80% of the VLT. Next, dogs from the group T have submitted to IET again. The maximal velocities (Vmax) at which achieved by the trained dogs in both IETs were determined. The group S did not undergo IETs or ETP. HRV was determined by the 24-hour-Holter at rest, before and on the 2˚, 4˚, 6å nd 8˚training weeks. To examine the HR impact on HRV, standard HRV variables were normalized to prevailing HR. VLT and Vmax rose in group T, indicating an improvement of dogs' aerobic and anaerobic capacity. The normalized standard HRV indexes were relatively attenuated since these variables had a reduction in the degree of correlation concerning an average HR. The ETP resulted in decreased resting heart rate and increased timedomain indices, highlighting the log-transformed square root of the mean sum of the

Conditioning Program Prescribed from the External Training Load Corresponding to the Lactate Threshold Improved Cardiac Function in Healthy Dogs

“…Three evaluators experienced in exercise physiology examined the curves and determined the velocity at which the lactate concentration showed an abrupt and exponential increase. The inflection point represents the beginning of an imbalance between lactate production and removal/metabolism [ 24 , 25 ]. The VLT obtained in IET-1 was used to prescribe the individual training routine.…”

“…The heart rate was evaluated by a 24 h Holter test using a Cardioflash ® (digital-Cardios Sistemas-São Paulo, Brazil) to capture the signals of cardiac electrical activity for 24 h, following the methodology previously published by our laboratory [ 24 , 26 ]. The electrocardiographic tracings were processed by a specific software (Cardio Manager S540, Cardios Sistemas, Brazil).…”

“…In studies with human athletes, exercise physiologists employ fitness protocols that were prescribed based on maximum oxygen consumption ( O 2 max) and lactate threshold (LT) for specifying the training program load aimed at improving systolic and diastolic function in healthy or sick individuals [ 18 , 19 , 20 , 21 ]. In veterinary medicine, relatively few studies [ 22 , 23 , 24 ] have used the individualized prescription of internal or external load for elaborating training protocols while evaluating their effects on the echocardiographic variables. Moreover, prolonged submaximal exercise to prevent or treat cardiovascular disease is still relatively limited, notably in dogs.…”

“…Our research group recently determined the LT in dogs subjected to the incremental exercise testing (IET) [ 23 , 24 , 26 ] to obtain the velocity corresponding to the LT (VLT). This variable was the reference used for establishing the external training load since it is considered more reliable compared to both the percentage of maximum oxygen consumption (%O 2 MAX) and the maximum heart rate (%HRMAX) [ 16 ].…”

“…This variable was the reference used for establishing the external training load since it is considered more reliable compared to both the percentage of maximum oxygen consumption (%O 2 MAX) and the maximum heart rate (%HRMAX) [ 16 ]. The training protocol improved aerobic capacity and increased heart rate variability after eight weeks of training [ 23 , 24 ].…”