Background
The frequent practices of physical exercises remain a crucial factor to decrease mortality and morbidity rates of cardiovascular plus other conditions. There likewise appear to be some gains from physical activities and enhancement of aerobic conditions. Although moderate exercise improves health conditions, there is consistent and recent evidence that strenuous or high-intensity exercise have even more substantial positive effects on lipid profiles, reducing about two times mortality rates for a decade. During the workout, numerous physiological adjustments take place to offer required supply of nutrients and oxygen to achieve the demands of muscular activity dictated by the role presented. Mostly, the cardiovascular changes during exercise have been evaluated expansively to give overall guidelines concerning the average or expected responses to different physiologic systems.
According to Becker (2013), findings, physiological variations that are present between men and women comprise weight, height, body composition (comprising muscle and fat mass), in addition to differences in hormones (such as progesterone, testosterone, and estrogen) plus hemoglobin levels. Concerning exercise capacity, the enriched capacity for augmented maximum oxygen uptake in males is usually quoted to explain the enhanced physical performance in men. Nevertheless, when persons are matched for lean muscle mass, age, and height, significant difference exist in the cardiovascular response to do workout on sex. Preceding work indicates variations materialize in the mechanisms leading to the heightening of cardiac performance while in aerobic exercise between sexes, in which females have showed a sharp increase in an ejection with a workout, and dissimilar to men, women showed no increase in stroke volume with physical activity. Further, women presented a lower age-related decline in Heart Rate (HR) reserve with age. Contrarily, men have demonstrated an increase in stroke work index and end diastolic volume index with age. It has been claimed that men have a greater dependence on preload and improved use of Frank-Starling mechanism while females depend on heart rate to increase cardiac output (Gladstone 110).
Today, the mainstream of this preliminary work has been recorded at rest and maximal exercises, leaving a significant scarcity of data about the variations in cardiovascular reaction to submaximal continuous-load exercise between men and women, since findings have chiefly been derived from submaximal workloads in a maximal exercise experiment. As such, many questions are still unanswered, including:
What are the primary mechanisms causing differences in cardiovascular reaction to exercise across sex margins?
Do known variations between genders become more evident or dissipate when the persons are non-sedentary?
Do decreases in cardiac function shown at peak exercise of women stay at submaximal intensities?
What compensatory mechanisms do women depend on in a trial to ameliorate limits?
Consequently, the objective of this study was to analyze the variations in cardiovascular response to physical activity between females and males. Cardiac output and its subcomponents, heart rate and stroke volume, along with the intra-arterial catecholamine and blood pressure reactions to exercise in males and females at rest and during average and dynamic intensity constant load-exercises have been examined (Theobald 85).
Hypothesis
It has been hypothesized that in spite of the same cardiac output during a moderate submaximal workout, stroke volume index will remain higher in males while females will present higher HR for that particular workload. On the contrary during rigorous exercise, women would demonstrate declined cardiac output because of incapability to accommodate the increased demand through enhanced HR. Moreover, women are anticipated to show elevated MAP and SBP compared to men (Becker 125).
Materials and Methods
Eighty-eight males and women aged between 25-55 years were invited to take part in this study. Males (n = 43) and females (n = 45) were recruited. Even though there was no variation in age cross sexes (n = 0.49) as anticipated, the males participants were healthier, taller, and had a higher BSA and BMI in comparison the female counterparts (p < 0.01) (Markil 215).
Measurement of Heart Rate Variability
Heart Rate Variability (HRV) measurements were designed, performed, and analyzed. Chest and limb were put in standard postures, and a 12-lead electrocardiogram was recorded. Once this procedure was concluded, participants rested flat for a minimum of 5 minutes in a quiet boardroom (Ramírez 17). Five minutes beat-to-beat heart rate data was samples 500 Hz frequency by utilizing a committed personal computer software to get digitalized recording of rate waves. A ventricular contraction contributes a heartbeat that as electrical depolarization contributes a result observed on the surface of the skin as QRS compound. The interval between consecutive rate waves portrays successive pulses. HRV were exempted from further evaluations if they had frequent ventricular or atrial ectopics (Gladstone 117).
Results
BSA = body surface area, BMI = body mass index, VO2 max, maximum oxygen uptake. Data are given as mean ± SD. P-value = Learners T-test male versus female
Gender differences in Heat Rate at Rest
At rest, there was no variation in VO2 (0.49). However, men contributors showed higher Q1 (p = 0.03) intermediated by a higher SV1 (p = 0.02). There was a tendency for the female partakers to have a higher heart rate, HR (p = 0.05). The male partakers similarly demonstrated a greater SBP (p = 0.02) without difference in DBP (p = 0.13) (Becker 35). Even though the SBP measured via the catheter and indicated many women could have been slightly hypertensive, the auscultation bracelet measurement elucidates they were normotensive. The increased SBP was likely because of the positioning of the atrial catheter and data were taken pre-exercise but not in an actual resting condition. The elevated SBP in male correspondence caused a higher MAP (p = 0.03). Because Q1 and MAP were both higher in men, there were no variations in SVR1 between both genders (p = 0.74). Male participants showed higher circulating NE levels (p = 0.04) against their female colleagues. Even though the oxygen partial pressure (PaO2) was the same between genders, the lower hemoglobin (Hb) concentration diminished the arterial oxygen composition (CaO2) and systematic oxygen transportation (SOT) in women correspondences (p < 0.03 was for Hb, CaO2 and p = 0.04 was for SOT). As well, the passive pressure of carbon dioxide (PaCO2) was greater in women participants (0.02) (Markil 241).
Where VO2 represent a volume of oxygen uptake; HR is heart rate; Q1 is cardiac index; SV1 is stroke volume index. SBP is systolic blood pressure (direct arterials). MAP stands for arterial pressure (direct arterials); AVO2 variance, arterial to venous O2 variation. SVRI means systematic vascular resistance index; DBP is diastolic blood pressure (direct arterial); SOT, systematic oxygen transport; PaO2, arterial partial pressure of oxygen; RPE, rating of obvious exertion; PaCO2 means the arterial passive pressure of carbon dioxide; CaO2 represents arterial oxygen composition (Gladstone 131).
Figure 1: Gender variances in the cardiac reaction to constant-load submaximal exercise (as cited in Becker 2013, p 164).
Gender variances in Heart Rate throughout moderate intensity constant-load exercise
The male partakers demonstrated an elevated VO2 (0.02) with an increased Q1 (p < 0.02) mediated by a high SV1 (0.02). In moderate intensity workout, the decreased oxygen transport capacity, as a result of lower Hb concentrations (p < 0.03), in women participants was enough to cause lower oxygen uptake and led to SOT mediated by a lower Q1 and CaO2 (Ramírez 39). Typical of at rest, the PaCO2 was greater in men participants (p < 0.02). Women also showed a trend to elevated HR (p = 0.07), though this variation was not sufficient enough to compensate for the reduced SV1 and consequently lower Q1 in women. Men participating presented a higher SBP (p < 0.13). As observed at rest, the difference response between females and males in MAP and Q1 did not contribute to a differential in SVR1 between genders (p = 0.42). Both EPI and NE levels were greater in the male partakers (p = 0.02). Lactate of blood in both reference line in both groups and balanced over the 9 min session (Theobald 113).
Figure 3: Lactate reaction to constant-load submaximal workout (Gladstone 2015, p 153)
Sex differentials in cardiovascular function in vigorous intensity constant-load workout
Regardless of being a consistent workload, men contributors presented a higher VO2. Men contributors similarly showed a higher Q1 intermediated by increased SV1 because there was no variance between the individuals for HR. SOT and CaO2 again stayed lower and possibly resulted to the lower VO2 in women contributors. Further, PaCO2 was elevated in men. Similarly, the male participants depicted an increased SBP which caused a higher MAP amount of work as there was again no variance in DBP. In contradiction to the no differential at the moderate intensity amount of exercise, men participants showed a lower SVR1 in comparison with the female counterparts. Blood lactate endured to amass until the ending of exercise in both genders but tended to be lesser in women (Markil 320).
Sex differentials in cardiovascular function in constant-load exercise adjusting for differences in peak power
Owing to the obvious difference in aerobic fitness between genders and the probable variations in muscle mass, adjustment in cardiovascular features was dictated by maximum power output. Even though the comparative intensities were similar between genders, 40% and 70% of the maximum workload, responses were also compared as a function of the absolute power performed by per subject, as in Table 3.
When adjusted for Watts, absolute VO2 did not differ between sexes, demonstrating that the comparative intensity, both vigorous and moderate, were identical groups. During bot vigorous and moderate workout, women seemed to be at an elevated cardiopulmonary demand, as HR, VO2, SV, AVo2 and Q differences rectified for watts were higher in comparison with male colleagues (Theobald 165). Energy and work expenses were considerably higher in men at both vigorous and moderate workloads. When correcting the differentials in wattage, moderate intensity showed no difference, although the energy expenditure for each watt was minimal in women at the vigorous intensity. No difference was observed in mechanical efficiency at the moderate intensity (23-percent for both) between genders. However at the rigorous workload females were somewhat more efficient (24% females vs. 23% males), and the delta efficiency led to females being somewhat more efficient with augmenting intensity while there was no alteration in males. In both exercises intensities, the ventilatory equal for CO2 and O2 was greater in females when rectified for watts (Gladstone 179).
Analysis
The results of this research insinuate that during constant-state exercise at relatively coordinated workloads of both vigorous and moderate submaximal intensity, women demonstrated lesser Q by decreased SV in comparison with men even in the case of the index for BSA. As well, the female contributors indicated reduced SBP leading to lower MAP. Despite these variations, the SVR was still the same at moderate intensity and rest but only differed during vigorous-intensity exercises between female and male participants insinuating that the homeostatic and regulation relation between heart rate (blood pressure) and cardiac output is attained via differential mechanisms in men and women (Becker 207).
Conclusion
The result of this research indicates that a different regulation of heart rates (cardiovascular function) between genders during continuous-load submaximal exercise, agreeing with previous determinations of differentials in heart rate at rest and maximal workout. Rectifying for variations in size, women showed a reduced SV; they could not compensate for via increases in heart rate since Q1 and SV1 are both minimal in females (Markil 362). When rectified for wattage, women showed an increased HR, Q, and SV with elevated peripheral oxygen withdrawal as a compensatory mechanism in comparison with males emphasizing greater cardiac work task required to meet a similar physical work demand. The limits of stroke volume may be the outcome of female's diminished considerate response and elevated basal vasodilatory condition, proven by lower catecholamine intensities in women at rest and by submaximal exercise. Furthermore, both genders had identical SVR whereas MAP and SBP were higher in males suggesting the association between Q and MAP is the same across genders. The data are consistent with previous studies indicating sex differentials in the regulation of arterial tone and expand these studies to recommend that the result of the difference in control is the same.
Work Cited
Becker, Jordan. The Effectiveness of the StreetStrider as an Exercise Modality for Healthy Adults. 2013. Print.
Gladstone, Robert. "Physical Activity Exercise's Effects on the Heart " 6 June 2015. Web. 11 Mar. 2016.
Markil, Nino. Comparison of Acute Heart Rate changeability Responses to Relaxation Only versus Relaxation Preceded by Hatha Yoga. 2014. Print.
Ramírez, Robinson. "PT246 Effect of Commended Physical Activity Dosage on Maternal Metabolic Outcomes in Pregnant Latina Women." Global Heart 9.1 (2014). Web. 11 Mar. 2016.
Theobald, H. "Effect of Heart Rate on Long-term Mortality among Men and Women." Acta Cardiologica 62.3 (2012): 271-75. Web. 11 Mar. 2016.
