Relationships between self-reported health related quality of life and measures of standardized exercise capacity and metabolic efficiency in a middle-aged and aged healthy population.
BACKGROUND
The purpose of this study was to evaluate to what extent self-reported health related quality of life (HRQL), assessed by the Swedish standard version of the Medical Outcome Study Short-Form 36 (SF-36), is related to measured exercise capacity and metabolic efficiency in a cohort of healthy subjects from the Gothenburg area of Sweden.


METHODS
Individuals were invited to take part in the evaluation where HRQL was compared with the maximal power output expressed in Watts assessed during a standardized treadmill test with incremental work loads. Whole body respiratory gas exchanges (CO2/O2) were simultaneously measured. Estimate of metabolic efficiency was derived from oxygen uptake per Watt produced (ml O2/min/W) near maximal work.


RESULTS
The health status profile in the current population largely agreed with normative data from an age- and gender-matched reference group, although some measured scores were slightly better than reference scores. Males and females had a similar relationship between energy cost (ml O2/min) for production of maximal work (W), while the regressions for maximal exercise power and age were significantly different between males and females (p < 0.01). The overall metabolic efficiency was the same in individuals between 40 and 74 years of age (10.4 +/- 0.07 ml O2/min/ Watt). Maximal exercise power was only related to the SF-36 subscale physical functioning (PF), but unrelated to other physical subscales such as role limitations due to physical problems, good general health and vitality. There was also a discrepancy between measured maximal power and PF in many subjects, particularly in males who experienced either intact or severely reduced PF.


CONCLUSIONS
Our results demonstrate that simultaneous measurements of self-reported and objective measures of PF should add a more integrated view for evaluation of therapeutic effectiveness, since the overall correlation was poor between objective and subjective scores among individuals.
D000368:Aged; D017079:Exercise Tolerance; D005260:Female; D006304:Health Status; D006305:Health Status Indicators; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption; D011659:Pulmonary Gas Exchange; D011788:Quality of Life