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The purpose of this study was to examine whether activities parallel to daily living (APDL) constitute a determinant index of cardiorespiratory fitness in patients with chronic obstructive pulmonary disease (COPD).Four functional physical fitness parameters were investigated in 38 male patients (mean age 69.8 ± 6.7 years) with moderate to severe COPD. The parameters measured were muscular strength (grip strength), muscular endurance strength (arm curl, keeping a half-squat position) and regulation (walking around two cones). In addition, cardiorespiratory fitness was measured using a 6-min walking distance test (6MWD) and peak oxygen uptake (VO2peak) was measured during bicycle ergometer testing. Maximal inspiratory pressure (MIP) and maximal expiratory pressure were measured so as to quantify respiratory muscle strength.There were significant correlations (P < 0.05) between the VO2peak, muscular endurance, pulmonary function and respiratory muscle strength. There were also significant correlations of VO2peak to muscular endurance, muscular strength, muscular endurance strength and regulation. In stepwise multiple regression analysis, per cent predicted forced expiratory volume in 1 s and MIP appeared to be significant determinants of VO2peak, showing a total variance of 56% (P < 0.05). For the 6MWD, the significant determinants were forced vital capacity, MIP and performance in the half-squat test, showing a variance of 59% (P < 0.05).The results suggest that cardiorespiratory fitness is strongly affected by MIP, pulmonary function and muscular endurance strength, as APDL depend on lower-limb use.