engleski

Treadmill exercise for assessment of functional capacity in canine athletes

There are different methods to determine or monitor functional capacity in order to plan a suitable exercise programme. General factors of functional capacity are oxygen consumption (VO2) and heart rate (HR). Heart rate is considered a useful indicator of relative cardiovascular load, and therefore may be used as an indicator of exercise intensity (1). Parameters commonly used for evaluating the aerobic capacity are the maximum oxygen uptake (VO2max) and anaerobic (lactate) threshold. Lactate concentrations in blood increase during physical exercise of certain intensity and can be measured using two different methods: in a laboratory using the standard biochemical analysers and by hand-held portable lactate analysers. The main advantage of portable lactate analysers is simple handling and immediate results. VO2max is used to determine an individual’s maximal aerobic power and is an important predictor of endurance exercise performance. Since the VO2 maximum is proportional to the increase of HR during exercise, and increased VO2max is a sign of overall aerobic metabolic rate, prolonged exercise will cause increase in VO2max. By monitoring the HR frequency, conclusions may be inferred regarding changes in aerobic capacity. Variations in HR during activity correlate with changes of exercise intensity and may be recorded directly by radio-telemetry in dogs. By recording the heart rate during a training session or exercise, the relative heart rate to the intensity of the work load (% maximum heart rate) can be calculated. Determining the maximal heart rate (HRmax) is necessary for establishing a percentage of HR to HRmax that defines the exercise intensity. In dogs, different studies have reported differing HRmax : 300 BPM in a mixed breed group (2), and 318 BPM in racing Greyhounds (3). During agility competition a HRmax of 220 BPM was reported in dogs (1), but was 246 BPM during an incremental test in agility Border collies (4). It is generally accepted that a value of 300 BPM is a HRmax for dogs, but this is dependent on breed, exercise intensity and fitness status. Conconi et al. (5) developed a simple test and a method to determine the heart rate deflection point (HRdp). This non-invasive method is considered a reliable predictor of aerobic performance by many, concurrent with lactate threshold. HRdp is characterized by a distinctive differentiation or ‘deflection’ in the linear HR-work relationship or heart rate performance curve exhibited during progressive incremental exercise testing. This is visually manifested as a curvilinear response and is reported in the range of 88 to 94% of maximum HR for athletes in various sports and under different protocols. The use of HRdp in sport dogs was first described in a study on agility Border Collies (4), and recently also in sedentary Beagles (6) and detection dogs (7). In a study of agility dogs, fourteen healthy Border Collies aged 3.9 (± 2.3) years were submitted to incremental treadmill exercise. Heart rates were recorded using Polar System fixated around their chest. Each subject started the protocol by walking at a speed of 5 km/h in order to warm up. After warming up the treadmill speed was gradually increased every 30 seconds for 0.5 km/h. The slope was adjusted to 5% for all dogs. Heart rate deflection point (HRdp) and the speed at deflection point (Vdp) were determined using two methods: independent visual inspection and computer-aided regression analysis within Polar PRO trainer software. After the completion of each dog’s running session, the HR/speed relationship was graphically displayed. The HRdp and Vdp were identified as the point at which the values of the slope of the linear portion of the speed/HR relationship began to decline and the values of the intercept on the y-slope began to increase. Average HRdp was 183 i.e. 184 BPM (depending on the method used), 80% of the maximum average heart rate achieved in this study which was 230 BPM. However, the range of individual HRdp was between 162 and 229, which indicates the need of individual approach to assess physiological parameters of each sport dog.

exercise, treadmill, physiology

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