Integrate Acute Cardiovascular Adjustments to Exercise: Impact of Exercise Type and Population Characteristics

STUDY1: Cardiovascular, metabolic and muscular responses during incremental cycle ergometer test: gender, age and pathology-related differences. The literature on cardiovascular responses to incremental exercise test (IET) does not unanimously clarify the role of stroke volume changes in the enhancement of cardiac output. The aim of the present project was to characterize the cardiovascular response, in terms of Heart Rate (HR), Stroke Volume (SV) and Cardiac Output (CO), during cycle-ergometer incremental tests, in young and aged subjects of both sexes with and without pathology. IET on cycle ergo-meter started with a load of 40 W for 3 min followed by 10 or 20 W increments each minute, for females and males, respectively, up to voluntary exhaustion. We recruited sedentary young (HY), elderly (HE) and diabetic subjects(D2), both male (M) and female (F). HEM/F and HYM/F: 13 males,12 females per groups; sedentary, non-smokers, no evidence of chronic complications or presence of other pathologies. D2M/F: 8 males, 4 females ; sedentary (International Physical Activity Questionnaire <1000 MET min*week), diet and/or oral hypoglycaemic agents, diabetes diagnosis at least 1 year before (15.1±6.9y D2M 11.1±4.9y D2F) and, HbA1c 7.1±0.5 % D2M and 6.4±2.2 D2F, HDL 53.1±10.1 mg/dL D2M and 47.5±17.4 mg/dL D2F, Total Cholesterol 142.8±20.9 mg/dL D2M and 140.8±48.5 mg/dL D2F, non-smokers, no evidence of chronic complications. Every subject was equipped, for all test and part of recovery, with a cardiovascular monitoring instrument (Portapres, TNO), that collects data about Blood Pressure (SAP, Systolic Arterial Pressure. DAP Diastolic Arterial Pressure. Mean Arterial Pressure), HR (Heart Rate), SV (Stroke Volume), CO (Cardiac Output), TPR (Total Peripheral Resistance) a NIRS device on vastus lateralis muscle (ISS, Oxiplex) for muscular oxygen extraction (DeOxy Hb, deoxygenated hemoglobin), and a gas exchange analyzer (QuarkB2 COSMED, IT ) which reports VO2 uptake, CO2 production, Tidal Volume (VT) etc. Moreover at the beginning and at the end of the exercise we collected a single drop of blood from the finger/ear to test LA+ (lactate blood concentration, by Accutrend) and Hb (Hemoglobin blood concentration), the concentrations are evaluated to consider the lactate accumulation after an exhaustive exercise and possible changes in hemoglobin concentration. VO2max is an important determinant of endurance performance, and the pathology-related effect consists in an impairment of aerobic capacity in D2M, who have an oxygen uptake lower than HYF, and of D2F who have the lowest VO2max. The most consistent result regards the SV response. In this study the HEM SV response is peculiar, while in all other groups SV increases progressively with the enhancement of workload; moreover in HEM TPR after the initial fall (from 0.9 MU to 0.6 MU) keeps the same value until the end of exercise. Thus, Diabetic subjects show a compensative strategy by the enhancement of oxygen extraction at muscular level at the peak of exercise with the largest increase (35% over the basal value, D2M).The strong decrease in SV of HEM at 80% could be caused by relatively compromised vasodilator function, which does not keep proportional to the effort, since TPR fails to decrease as in the other groups. STUDY2: Gender, age and Pathology-related factors in acute cardiovascular adjustments to dynamic resistance and isometric exercise Strength training has been shown to be of great value in preventing and managing diseases and promoting health. It increases muscle force, lose fat, under regulate blood pressure, etc. There are a lot of data about resistive exercise, but it is still important to clarify the contributions of central and peripheral adjustments in response to leg press exercise in order to quantify and interpret the whole adaptation to this kind of stimuli and adapt training strategy per gender, age or presence of pathology. The aim of the present project is to characterize hemodynamic acute responses during leg press exercise, matched with metabolic and peripheral data, in different subjects. Dynamic Exercise The individual theoretical maximal load for 1 repetition (1RM) on the leg press was determined according to Brzycki formula .Each subject performed three series of dynamic resistance exercise at 70% of previously determined 1RM, separated by 10 min resting: two series with 12 repetitions and the third series with repetitions to voluntary exhaustion in order to estimate the individual maximal performance on the specific exercise. Equipment and groups were the same of study 1. In addition FBF (Femoral Blood Flow), coupling diameter and blood velocity data of the vessel was collected with Echo Doppler P 50. Cardiovascular acute adaptations in terms of SV and CO seem to be dependent on age. After an initial decrease (10” sec of exercise) HYM/F are able to increase the SV response during the entire exercise period, while HEM/F and D2M/F, display a drop until the end of exercise; at 20” sec recovery both HY and HE/D attain the same value. It is also possible that HEM and HEF helped their limb movements by contracting abdominal muscles in the concentric phase of the movements, thus raising intra abdominal pressure and decreasing venous return to the heart. The oxygen consumption at the end of the effort in males groups show an peculiar increase : HEM increases of 18%-20%, HYM 12%-22%, at least for the first 30 sec of recovery, maintains the peak value even during the recovery for 30 sec. This mechanism it’s slightly present also in females:HEF increases by 9%, HYF of 4%, in both cases only for the first 10 sec post exercise, D2F show that males with diabetes to maintain some sort of steady state but waning -12% -8%. The present study reports an excess of FBF after exercise especially for two groups: D2M and HYM (HEM group not available). D2F display a sort of plateau for some seconds, while HEM and HYF do not show any post exercise hyperemia. Diabetics groups, who exhibited the largest oxygen extraction at muscle level as compared with same sex young groups. Isometric Exercise The isometric exercise was performed with the same load used with resistance exercise, but each subject had to lift up the weight and maintain the squat contractions as long as he/she was able. HEM group did not perform this test. HYM and HYF during Isometric contractions use the same strategy of all other groups, they decrease SV during the effort, while in dynamic exercise they adjust the response in the opposite way. This is probably caused by the typical characteristic of isometric contractions on leg press where all dorsal and abdominal muscles, in addition to leg muscles participate in the effort, thus hampering venous return and reducing SV. STUDY 3 : SW “Square wave”: Constant Load Aerobic Exercise. Aerobic exercise is the most common activity in fitness world. Its role in reducing Cardiovascular risk factors, in enhancing fitness level, in maintaining mental health, etc... is undisputed. In research kinetics of aerobic exercise adaptations can be analyzed, that is the speed of each parameter in reaching new steady state values. Constant work rate tests (square wave) are suitable for studying cardiovascular, ventilator and gas exchange kinetics (8, 9). Measurement of these variables, especially VO2 by Quark (gas exchange analyzer), and Oxygen extractions (DeoxyHb) by NIRS (Near infrared spectroscopy), during transitions from rest to constant load exercise allows determination of the time constants (tau) or of the mean response time (MRT) characterizing the shift from baseline levels to new steady state values. Tau, MRT and the magnitude of change in VO2 are well correlated with the fitness state (10, 11). Priming exercise is a kind of warm up before the aerobic exercise session, it is also called prior exercise, heavy warm up exercise, because very often it consists in a high intensity warm up before a normal moderate aerobic exercise. To verify whether MRT is reduced during a bout of constant load exercise preceded by an identical exercise (priming effect) in different populations, to gain insight about the mechanisms leading to the priming effect. We recorded baseline values for 3 min with the subjects sitting still on the cycle ergometer saddle, and further 3 minutes while the subjects pedaled without load, to record the effects of movement per se and to obtain adequate warm up; after that, the load was raised and kept constant for six minutes at a value corresponding to 80% VO2max, at 60-70 rpm; after the subjects stopped pedaling, we kept collecting data during the recovery period, until reasonable recovery of basal conditions. This exercise was repeated 3 times, separated by 10 minute of recovery. CHF: 27 males, 2 females; sedentary (International Physical Activity Questionnaire <1000 MET min*week), NYHA type II/III chronic heart failure, all subjects wearing an automatic implanted defibrillator for safety reasons, CHF diagnosis at least 1 year before. HEM/F: 22 males,10 females and HYM/F 40 males, 11 females ; sedentary, non-smokers, no evidence of chronic complications or presence of other pathologies. D2M/F: 9 males, 4 females ; sedentary (International Physical Activity Questionnaire <1000 MET min*week), diet and/or oral hypoglycaemic agents, diabetes diagnosis at least 1 year before (15.1±6.9y D2M 11.1±4.9y D2F) and, HbA1c 7.1±0.5 % D2M and 6.4±2.2 D2F, HDL 53.1±10.1 mg/dL D2M and 47.5±17.4 mg/dL D2F, Total Cholesterol 142.8±20.9 mg/dL D2M and 140.8±48.5 mg/dL D2F, non-smokers, no evidence of chronic complications. Mean response time (MRT) is calculated, as the ratio between the integral of V’O2 deficit during the transient phase and V’O2 at steady state. VO2 response is quantitatively different among groups, which has been well documented in the literature, depending on age or presence of pathology. In the baseline condition VO2 is around 350 l/min in male and 300 l/min in female, and the increase to the steady state during exercise is different among the groups. Young subjects display the greater increase: 2,0 l male, and 1,2 l female; elderly groups show lower increase, 1,3 l male and 0,7 l female; Diabetic groups behave like the Elderly. The kinetics tends to be similar per age but not per sex, HEM and HEF are significantly different than HYF and HYM. Thus it becomes clear that HYM, HEM, D2M adapt faster than HYF, HEF, D2F and CHF much slower. In addition, if the male groups tend to speed up quite slightly their adaptation in the second trail, this tendency is overt in CHF. Most CHF subjects increased the speed of VO2 kinetics: the average values of MRT were 44,7 s in SW1 and 38,1 s in SW2, a significant decrease by 15%. In the young, only heavy (not light) exercise is preconditioning, and only for a following heavy (not light) exercise bout. In the healthy older, heavy exercise affects even a following light exercise bout. In CHF, even a light exercise affects a following light exercise bout.