Relationship between rest-activity rhythms and cardiorespiratory fitness in middle-aged workers: a cross-sectional study with non-parametric analysis using accelerometers worn on the thigh.

BACKGROUND: Rest-activity rhythms are directly related to health risks, but there are limited objective methods to assess them. This study aimed to investigate the relationship between rest-activity rhythms and cardiorespiratory fitness (CRF) in middle-aged workers. METHODS: Peak oxygen uptake was measured on a treadmill to assess CRF in 254 middle-aged workers who were divided into low, medium, and high-CRF groups based on tertiles. Participants were asked to wear an accelerometer (activPAL) on their thighs for 1 week, and the logarithmically transformed acceleration data were used for the analysis of a 24-hour rest-activity rhythm. Sex, age, body mass index, occupation, smoking status, and alcohol consumption were used as covariates in Model 1, with Model 2 also including walking count on non-workdays. Repeated measures analysis of variance was used to compare time course of rest-activity rhythms changes on workdays between groups, and post-hoc tests were conducted using Bonferroni's correlation. RESULTS: Higher CRF correlated with increased physical activity. In model 1, higher CRF showed improved interdaily stability, but the significant difference disappeared in model 2 after adjusting for non-workday walking counts. A time-course group comparison showed that the high group had significantly higher activity levels than those of the low group from 6:00 to 8:59 and 17:00 to 17:59 and the medium group from 6:00 to 7:59 and 19:00 to 19:59. CONCLUSIONS: Workers who have better rest-activity rhythms and engage in higher levels of physical activity on workdays tend to have higher CRF levels. Regular daily routines, influenced by physical activity during holidays, can positively impact cardiopulmonary endurance.

Estimation methods to detect changes in cardiorespiratory fitness due to exercise training and subsequent detraining.

PURPOSE: To determine whether estimated maximal oxygen consumption ([Formula: see text]) can detect cardiorespiratory fitness (CRF) changes by behavioral modifications. This study compared changes in measured [Formula: see text]O2max (m[Formula: see text]O2max) through exercise intervention with e[Formula: see text]O2max using a multiple regression model (MRM) and linear extrapolation method (LEM). METHODS: A cross-sectional analysis involving 173 adults was conducted to establish an MRM by including age, sex, body mass index, questionnaire score, heart rate (HR) from step test, and m[Formula: see text]O2max. Subsequently, 15 men participated in an intervention experiment comprising an 8-week, high-intensity interval training, followed by 8-week detraining, and completed anthropometric measurements, questionnaires, step tests, and m[Formula: see text]O2max tests. m[Formula: see text]O2max changes throughout the intervention were compared to e[Formula: see text]O2max changes calculated using the MRM and LEM. The LEM used the HR during the step test with constant values (predetermined [Formula: see text]O2), such as the Chester step test. RESULTS: Inclusion of the step test HR in a questionnaire-based MRM improved the estimation power, although the MRM underestimated higher m[Formula: see text]O2max values. In the intervention, m[Formula: see text]O2max increased by 20.0 ± 14.1% (P < 0.01) and subsequently decreased by 9.5 ± 6.6% (P < 0.01) after exercise training and detraining, respectively. Significant method × time interactions were observed between m[Formula: see text]O2max and e[Formula: see text]O2max in the MRM but not in the LEM, i.e., an apparent systematic error (underestimation of high values) of the MRM was absent in the LEM, although the correlation between m[Formula: see text]O2max and e[Formula: see text]O2max using the LEM was moderate. CONCLUSION: e[Formula: see text]O2max, particularly using the MRM with HR as an explanatory factor, is not an appropriate method for detecting CRF changes along with behavioral modifications. CLINICAL TRIAL REGISTRATION: Registered number, UMIN000041031; Registered date, 2020/07/08; URL, https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000046855.

Association of sitting time and cardiorespiratory fitness with cardiovascular disease risk and healthcare costs among office workers.

Evidence of the impact of domain-specific sitting time (ST) and cardiorespiratory fitness (CRF) on cardiovascular disease (CVD) risk is currently limited. This study aimed to examine the associations between CRF and domain-specific STs in relation to CVD risk and annual healthcare costs among office workers. This cross-sectional study included 1,749 workers from an insurance company. The Worker's Living Activity-time Questionnaire was used to measure the domain-specific STs, including occupational ST and non-working day ST. Additionally, estimated maximal oxygen uptake as the CRF data was calculated using a validated equation: 59.96 - 0.23 × age + 7.39 × sex - 0.79 × body mass index + 0.33 × physical activity score. The company provided medical checkup results for CVD risk factors and healthcare costs. Multiple logistic regression analyses were used to calculate the odds ratios (ORs) for CVD risk. Significantly lower ORs for CVD risk were seen only with high CRF levels, and it was also associated with low annual healthcare costs. There were no associations between domain-specific STs and annual healthcare costs. Further explorations of domain-specific STs, physical activity, and health risks are warranted, and guidelines should focus on increasing CRF to prevent CVD risk among office workers.

Association of cardiorespiratory fitness with the risk factors of cardiovascular disease: Evaluation using the Japan step test from the National Institute of Occupational Safety and Health.

OBJECTIVE: Cardiorespiratory fitness (CRF) is an important factor for evaluating cardiovascular disease (CVD) risk. We recently developed a novel method (National Institute of Occupational Safety and Health, Japan step test [JST]) for evaluating CRF in workers; its criterion validity has been investigated. However, its association with health risk must be confirmed before its application in the workplace. Therefore, we aimed to determine the association of JST-evaluated CRF with the prevalence of CVD risk among Japanese workers. METHODS: For CRF evaluation, working adults completed the JST, which comprised a 3-minute stepping exercise and a 2-minute recovery period. Data on CVD risk factors and clinical history were collected through medical certification within 1 year from the date of the JST measurements. Participants were divided into three groups for multiple logistic regression analyses based on the JST values (low, moderate, and high). Odds ratios (ORs) for the prevalence of CVD risk were calculated. RESULTS: We recruited 885 working adults (46.4% women). The prevalence of CVD risk in the total population was 18.6%. When compared to the reference group (low CRF), the ORs for CVD risk prevalence after adjustments for lifestyle factors (smoking status, alcohol consumption status, and exercise habits) were 0.42 (95% confidence interval [CI], 0.28-0.63) and 0.29 (95% CI, 0.18-0.45) for the moderate and high groups, respectively. CONCLUSION: An inverse association was noted between the JST-evaluated CRF and CVD risk prevalence. JST may be helpful for identifying workers at risk for CVD development.

Improved VO2max Estimation by Combining a Multiple Regression Model and Linear Extrapolation Method.

Maximal oxygen consumption (VO2max) is an important health indicator that is often estimated using a multiple regression model (MRM) or linear extrapolation method (LEM) with the heart rate (HR) during a step test. Nonetheless, both methods have inherent problems. This study investigated a VO2max estimation method that mitigates the weaknesses of these two methods. A total of 128 adults completed anthropometric measurements, a physical activity questionnaire, a step test with HR measurements, and a VO2max treadmill test. The MRM included step-test HR, age, sex, body mass index, and questionnaire scores, whereas the LEM included step-test HR, predetermined constant VO2 values, and age-predicted maximal HR. Systematic differences between estimated and measured VO2max values were detected using Bland-Altman plots. The standard errors of the estimates of the MRM and LEM were 4.15 and 5.08 mL·kg-1·min-1, respectively. The range of 95% limits of agreement for the LEM was wider than that for the MRM. Fixed biases were not significant for both methods, and a significant proportional bias was observed only in the MRM. MRM bias was eliminated using the LEM application when the MRM-estimated VO2max was ≥45 mL·kg-1·min-1. In conclusion, substantial proportional bias in the MRM may be mitigated using the LEM within a limited range.

Mg-dechelation activity in radish cotyledons with artificial and native substrates, Mg-chlorophyllin a and chlorophyllide a.

The Mg-dechelation activity in extracts from radish (Raphanus sativus L.) cotyledons was investigated using an artificial substrate, Mg-chlorophyllin a (Chlin) and the native substrate, chlorophyllide a (Chlide). In addition to a known a small molecular weight metal-chelating substance (MCS), Mg-releasing protein (MRP) was present when Chlin was used as the substrate. However, only MCS had Mg-dechelation activity with the native substrate. To examine the possibility of the dissociation of MRP into a protein moiety and a small molecular mass compound with an activity like MCS, extraction with low and high ionic strength buffers was carried out. No evidence was obtained that MCS is a moiety of MRP, however. Inhibitor studies showed that MCS and MRP had different susceptibilities to the inhibitors, especially to the chelators tiron and EDTA when Chlin was used as the substrate. Tiron had no effect on MRP, but it severely reduced MCS activity in both substrates. The activity of MRP increased during senescence, indicating the induction of MRP, while the activity of MCS was almost unchanged. These results suggest different reaction mechanisms by independent compounds. These findings suggest that MRP and MCS are present independently, and MCS is postulated to be a substance that catalyzes the Mg-dechelation reaction in the breakdown pathway of Chl, although MCS was not induced during senescence. The properties of MRP and MCS in relation to the small molecular mass substance obtained from strawberry fruit are also discussed.