Contribution of Body Mass Index Stratification for the Prediction of Maximal Oxygen Uptake.

The purpose of this study was to investigate whether modeling within separate body mass index (BMI) stratifications improves the accuracy of maximal oxygen uptake (VO2max) prediction compared to a model developed regardless of adults' BMIs. A total of 250 Taiwanese adults (total group, TOG) aged 22-64 years participated in this study, and were stratified into a normal group (NOG: 135), an overweight group (OVG: 69), and an obesity group (OBG: 46), according to the BMI classification recommended by the Taiwan Ministry of Health and Welfare. VO2max was directly measured on an electromagnetic bicycle ergometer. Using the participant's heart rate in the 3-min incremental step-in-place test and demographic parameters, VO2max prediction models established for four groups were TOG model, NOG model, OVG model, and OBG model, respectively. Compared with the TOG model, the OVG and OBG models had higher coefficients of determination and lower standard error of estimates (SEEs), or %SEEs. The validities of the NOG (r = 0.780), OVG (r = 0.776), and OBG (r = 0.791) models for BMI subgroups increased by 1.79%, 4.64%, and 8.22% respectively, and the reliabilities (NOG model: ICC = 0.755; OVG model: ICC = 0.765; OBG model: ICC = 0.779) increased by 3.18%, 3.27%, and 9.63%, respectively. These results suggested using separate models established in BMI stratifications can effectively improve the prediction of VO2max.

Low Cardiorespiratory Fitness, Muscular Fitness, and Flexibility Are Associated with Body Fat Distribution and Obesity Risk Using Bioelectrical Impedance in Taiwanese Adults.

In terms of public health, obesity and overweight have become major concerns worldwide. Nevertheless, regarding body composition, it is important to have a more precise understanding of the fat-to-muscle ratio. Hence, this study aimed to adopt bioelectrical impedance measurements to test body fat percentage (BF%) and to determine the associations between health-related physical fitness and both body fat (BF) distribution and BF obesity risk in Taiwanese adults. We conducted a cross-sectional study and reviewed data derived from Taiwan's Scientific Physical Fitness Survey. From the database, responses from 17,970 participants aged 23−64 years were collected in this study. Each participant completed a series of health-related physical fitness measurements, including cardiorespiratory fitness (3 min of a progressive knee-up and step (3MPKS) test), muscular fitness (hand-grip strength), and flexibility (sit-and-reach test). The BF% of each participant was assessed using the bioelectrical impedance analysis method. BF% was negatively associated with low performance on the 3MPKS (ß = 11.314, p < 0.0001 for men; ß = 12.308, p < 0.0001 for women), hand-grip strength (ß = 2.071, p < 0.0001 for men; ß = 0.859, p < 0.0001 for women), and sit-and-reach (ß = 0.337, p = 0.008 for women) tests but was positively associated with sit-and-reach (ß = −0.394, p = 0.004 for men). A risk of BF obesity for low performance of 3MPKS (odds ratio (OR) = 26.554, p < 0.0001 for men; OR = 25.808, p < 0.0001 for women), hand-grip strength (OR = 1.682, p < 0.0001 for men; OR = 1.234, p < 0.0001 for women), and sit-and-reach (OR = 1.142, p = 0.007 for women) tests was observed. These results suggest that low levels of cardiorespiratory fitness, muscular fitness, and flexibility are associated with an increased risk of BF obesity.

The Determination of Step Frequency in 3-min Incremental Step-in-Place Tests for Predicting Maximal Oxygen Uptake from Heart Rate Response in Taiwanese Adults.

The maximal oxygen uptake (VO2max) prediction models established by step tests are often used for evaluating cardiorespiratory fitness (CRF). However, it is unclear which type of stepping frequency sequence is more suitable for the public to assess the CRF. Therefore, the main purpose of this study was to test the effectiveness of two 3-min incremental step-in-place (3MISP) tests (i.e., 3MISP30s and 3MISP60s) with the same total number of steps but different step-frequency sequences in predicting VO2max. In this cross-sectional study, a total of 200 healthy adults in Taiwan completed 3MISP30s and 3MISP60s tests, as well as cardiopulmonary exercise testing. The 3MISP30s and 3MISP60s models were established through multiple stepwise regression analysis by gender, age, percent body fat, and 3MISP-heart rate. The statistical analysis included Pearson's correlations, the standard errors of estimate, the predicted residual error sum of squares, and the Bland-Altman plot to compare the measured VO2max values and those estimated. The results of the study showed that the exercise intensity of the 3MISP30s test was higher than that of the 3MISP60s test (% heart rate reserve (HRR) during 3MISP30s vs. %HRR during 3MISP60s = 81.00% vs. 76.81%, p < 0.001). Both the 3MISP30s model and the 3MISP60s model explained 64.4% of VO2max, and the standard errors of the estimates were 4.2043 and 4.2090 mL·kg-1·min-1, respectively. The cross-validation results also indicated that the measured VO2max values and those predicted by the 3MISP30s and 3MISP60s models were highly correlated (3MISP30s model: r = 0.804, 3MISP60s model: r = 0.807, both p < 0.001). There was no significant difference between the measured VO2max values and those predicted by the 3MISP30s and 3MISP60s models in the testing group (p > 0.05). The results of the study showed that when the 3MISP60s test was used, the exercise intensity was significantly reduced, but the predictive effectiveness of VO2max did not change. We concluded that the 3MISP60s test was physiologically less stressful than the 3MISP30s test, and it could be a better choice for CRF evaluation.

Development and Validation of 3 Min Incremental Step-In-Place Test for Predicting Maximal Oxygen Uptake in Home Settings: A Submaximal Exercise Study to Assess Cardiorespiratory Fitness.

The purpose of this research was to develop the 3 min incremental step-in-place (3MISP) test for predicting maximal oxygen uptake (V.O2max). A total of 205 adults (20-64 years) completed the 3MISP and V.O2max tests. Using age, gender, body composition (BC) including percent body fat (PBF) or body mass index (BMI), and with or without heart rate (HR) at the beginning of exercise (HR0) or difference between HR at the third minute during the exercise and the first minute post exercise (ΔHR3 - HR4) in the 3MISP test, six V.O2max prediction models were derived from multiple linear regression. Age (r = -0.239), gender (r = 0.430), BMI (r = -0.191), PBF (r = -0.706), HR0 (r = -0.516), and ΔHR3 - HR4 (r = 0.563) were significantly correlated to V.O2max. Among the six V.O2max prediction models, the PBF model∆HR3 - HR4 has the highest accuracy. The simplest models with age, gender, and PBF/BMI explained 54.5% of the V.O2max in the PBF modelBC and 39.8% of that in the BMI modelBC. The addition of HR0 and ∆HR3 - HR4 increases the variance of V.O2max explained by the PBF and BMI models∆HR3 - HR4 by 17.98% and 45.23%, respectively, while standard errors of estimate decrease by 10.73% and 15.61%. These data demonstrate that the models established using 3MISP-HR data can enhance the accuracy of V.O2max prediction.