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

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 (β = 11.314, p < 0.0001 for men; β = 12.308, p < 0.0001 for women), hand-grip strength (β = 2.071, p < 0.0001 for men; β = 0.859, p < 0.0001 for women), and sit-and-reach (β = 0.337, p = 0.008 for women) tests but was positively associated with sit-and-reach (β = −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.

Associations of Health-Related Physical Fitness with Waist Circumference and Abdominal Obesity Risk in Taiwanese Adults

In this study, we aimed to determine the associations among health-related physical fitness measurements, waist circumference (WC), and abdominal obesity risk in Taiwanese adults. We conducted a cross-sectional study based on data from the 2017 Taiwan Scientific Physical Fitness Survey (the TSPFS). We collected the responses from 17,973 participants (7907 men and 10,066 women) aged 23–64 years for this study. The participants completed the study protocol with a standardized structural questionnaire and a series of health-related physical fitness measurements. The fitness measurements included cardiorespiratory fitness (measured by a 3-min progressive knee-up and step test), muscular fitness (measured by a hand grip strength test), and flexibility (measured by a sit-and-reach test). Our anthropometric measurements included height, weight, WC, hip circumference (HC), body mass index (BMI), and waist-to-hip ratio (WHR). We identified the quartiles of the health-related physical fitness results as the dependent variable in the multiple linear and multiple logistic regression analysis to determine the associations of the physical fitness measurements with WC distribution and abdominal obesity risk. We also considered the dose–response relationship. We found that cardiorespiratory fitness, relative grip strength, and flexibility were each significantly negatively associated with WC, but absolute grip strength was significantly positively associated with WC. We also found that higher levels of cardiorespiratory fitness, relative grip strength, and flexibility were each associated with a lower risk of abdominal obesity. Moreover, our secondary finding was of a dose–response relationship between physical fitness performance, WC, and abdominal obesity risk. In short, health-related physical fitness was an effective predictor of waist circumference for both sexes of Taiwanese adults, and higher levels of health-related physical fitness were associated with lower risks of abdominal obesity in Taiwanese adults.

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 (VO_2max) 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., 3MISP_30s and 3MISP_60s) with the same total number of steps but different step-frequency sequences in predicting VO_2max. In this cross-sectional study, a total of 200 healthy adults in Taiwan completed 3MISP_30s and 3MISP_60s tests, as well as cardiopulmonary exercise testing. The 3MISP_30s and 3MISP_60s 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 VO_2max values and those estimated. The results of the study showed that the exercise intensity of the 3MISP_30s test was higher than that of the 3MISP_60s test (% heart rate reserve (HRR) during 3MISP_30s vs. %HRR during 3MISP_60s = 81.00% vs. 76.81%, p < 0.001). Both the 3MISP_30s model and the 3MISP_60s model explained 64.4% of VO_2max, 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 VO_2max values and those predicted by the 3MISP_30s and 3MISP_60s models were highly correlated (3MISP_30s model: r = 0.804, 3MISP_60s model: r = 0.807, both p < 0.001). There was no significant difference between the measured VO_2max values and those predicted by the 3MISP_30s and 3MISP_60s models in the testing group (p > 0.05). The results of the study showed that when the 3MISP_60s test was used, the exercise intensity was significantly reduced, but the predictive effectiveness of VO_2max did not change. We concluded that the 3MISP_60s test was physiologically less stressful than the 3MISP_30s test, and it could be a better choice for CRF evaluation.

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 (VO_2max) 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. VO_2max 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, VO_2max 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 VO_2max.