College of Health and Human Services, University of North Carolina at Charlotte, 9201 University City Blvd, Charlotte, NC, 28223, USA.
Department of Kinesiology, California State University, Long Beach, Long Beach, CA, USA.
Int J Behav Nutr Phys Act. 2020 Nov 10;17(1):137. doi: 10.1186/s12966-020-01045-z.
In younger adults (i.e., those < 40 years of age) a walking cadence of 100 steps/min is a consistently supported threshold indicative of absolutely-defined moderate intensity ambulation (i.e., ≥ 3 metabolic equivalents; METs). Less is known about the cadence-intensity relationship in adults of middle-age.
To establish heuristic (i.e., evidence-based, practical, rounded) cadence thresholds for absolutely-defined moderate (3 METs) and vigorous (6 METs) intensity in adults 41 to 60 years of age.
In this cross-sectional study, 80 healthy adults of middle-age (10 men and 10 women representing each 5-year age-group between 41 to 60 years; body mass index = 26.0 ± 4.0 kg/m) walked on a treadmill for 5-min bouts beginning at 0.5 mph and increasing in 0.5 mph increments. Performance termination criteria included: 1) transitioning to running, 2) reaching 75% of age-predicted maximum heart rate, or 3) reporting a Borg rating of perceived exertion > 13. Cadence was directly observed (i.e., hand tallied). Intensity (i.e., oxygen uptake [VO] mL/kg/min) was assessed with an indirect calorimeter and converted to METs (1 MET = 3.5 mL/kg/min). A combination of segmented regression and Receiver Operating Characteristic (ROC) modeling approaches was used to identify optimal cadence thresholds. Final heuristic thresholds were determined based on an evaluation of classification accuracy (sensitivity, specificity, positive and negative predictive value, overall accuracy).
The regression model identified 101.7 (95% Predictive Interval [PI]: 54.9-110.6) and 132.1 (95% PI: 122.0-142.2) steps/min as optimal cadence thresholds for 3 METs and 6 METs, respectively. Corresponding values based on ROC models were 98.5 (95% Confidence Intervals [CI]: 97.1-104.9) and 117.3 (95% CI: 113.1-126.1) steps/min. Considering both modeling approaches, the selected heuristic thresholds for moderate and vigorous intensity were 100 and 130 steps/min, respectively.
Consistent with our previous report in 21 to 40-year-old adults, cadence thresholds of 100 and 130 steps/min emerged as heuristic values associated with 3 and 6 METs, respectively, in 41 to 60-year-old adults. These values were selected based on their utility for public health messaging and on the trade-offs in classification accuracy parameters from both statistical methods. Findings will need to be confirmed in older adults and in free-living settings.
在年轻成年人（即年龄<40 岁）中，100 步/分钟的步行步速是一个始终支持的绝对定义的中度强度步行的阈值（即≥3 代谢当量；METs）。对于中年成年人的步速与强度关系，人们知之甚少。
为 41 至 60 岁的成年人确定绝对定义的中度（3 METs）和剧烈（6 METs）强度的启发式（即基于证据、实用、全面）的步速阈值。
在这项横断面研究中，80 名健康的中年成年人（10 名男性和 10 名女性，代表 41 至 60 岁之间的每个 5 岁年龄组；体重指数为 26.0±4.0 kg/m）在跑步机上进行 5 分钟的小跑步，速度从 0.5 英里/小时开始，每 0.5 英里/小时递增一次。运动终止标准包括：1）过渡到跑步，2）达到年龄预测最大心率的 75%，或 3）报告 Borg 感知用力等级>13。步速通过直接观察（即手动计数）来确定。强度（即摄氧量[VO] mL/kg/min）使用间接热量计评估，并转换为 METs（1 MET=3.5 mL/kg/min）。使用分段回归和接收器操作特征（ROC）建模方法的组合来确定最佳的步速阈值。最终的启发式阈值是基于对分类准确性（敏感性、特异性、阳性和阴性预测值、总准确性）的评估来确定的。
回归模型确定了 101.7（95%预测区间[PI]：54.9-110.6）和 132.1（95%PI：122.0-142.2）步/分钟分别为 3 METs 和 6 METs 的最佳步速阈值。基于 ROC 模型的相应值为 98.5（95%置信区间[CI]：97.1-104.9）和 117.3（95%CI：113.1-126.1）步/分钟。考虑到两种建模方法，中度和剧烈强度的选定启发式阈值分别为 100 和 130 步/分钟。
与我们之前在 21 至 40 岁成年人中的报告一致，在 41 至 60 岁成年人中，100 和 130 步/分钟的步速阈值分别成为与 3 和 6 METs 相关的启发式值。这些值是基于它们在公共卫生信息传递方面的实用性以及两种统计方法的分类准确性参数的权衡选择的。需要在老年人和自由生活环境中进一步证实这些发现。
