HFpEF (heart failure with preserved ejection fraction) is a metabolic and cardiovascular illness with noncardiac components. For a study, the researchers sought to determine the metabolic cost of starting exercise in people with and without HFpEF, as well as the functional effects. Individuals with hemodynamically verified HFpEF from the Massachusetts General Hospital Exercise Analysis (MGH-ExS) and community-dwelling participants from the Framingham Heart researches were included in the prospective cohort process (FHS). The research began in April 2016 and will conclude in November 2020. Internal work (IW) is a metric for the number of work equivalents needed to start a movement. The cost of starting exercise (IW) in patients with HFpEF (MGH-ExS) and community-dwelling persons (FHS) was calculated using breath-by-breath oxygen uptake (Vo2) measurements and Vo2-work rate relationships. The correlation between IW and clinical/hemodynamic parameters was estimated using linear regression. 184 (5.7%) of the 3,231 patients had HFpEF and were from MGH-ExS, while 3,047 (94.3%) were from FHS and lived in the community. 86 (47%) of the MGH-ExS cohort were female, with a median (interquartile range) age of 63 (53-72) years and a median (interquartile range) peak Vo2 level of 13.33 (11.77-15.62) mL/kg/min. The median (interquartile range) peak Vo2 level in the FHS cohort was 22.2 (17.85-27.35) mL/kg/min, with 1,620 (53%) women, a median (interquartile range) age of 54 (48-60), and a median (interquartile range) peak Vo2 level of 22.2 (17.85-27.35) mL/kg/min. IW was higher in HFpEF patients, accounting for 27% (interquartile range, 21% -39%) of total effort (IW + assessed external workload on the cycle), compared to 15% (interquartile range, 12% -20%) in FHS participants. BMI explained the most variance in IW in MGH-ExS and FHS individuals with HFpEF (22% and 18%, respectively), while resting cardiac output and biventricular filling pressures were not significantly linked with variance in IW in patients with HFpEF. Despite equal resting hemodynamic parameters across IW, a higher IW in patients with HFpEF was related with a larger increase in left- and right-sided cardiac filling pressure during unloaded exercise. Internal work, a new BMI-related measure of the metabolic cost of commencing the activity, was shown to be higher in people with HFpEF than in middle-aged persons in the community, and it was linked to steep, early rises in heart filling pressures. When assessing functional intolerance in people at risk of or with HFpEF, the findings underline the necessity of characterizing diverse responses to exercise beginning.