College of Public Health and Human Sciences

PURPOSE: To identify reasonable heuristic (evidence-based, rounded, practical) cadence thresholds associated with absolutely-defined moderate (3 metabolic equivalents; METs) and vigorous (6 METs) intensity ambulation in middle-aged adults.

METHODS: Ten men and 10 women from each 5-year age group between 41-60 years of age performed a series of 5-min treadmill bouts separated by 2-min rest. Bouts began at 0.5 mph and increased in 0.5 mph increments until participants: 1) chose to run, 2) achieved 75% of their predicted maximum heart rate, or 3) reported a rating of perceived exertion (RPE) > 13. Cadence was determined via direct observation. Oxygen consumption (VO2) was measured using an indirect calorimeter. METs were calculated from the final two minutes of each stage by dividing VO2 in mL/kg/min by 3.5. Receiver Operator Characteristic (ROC) models were used to predict moderate and vigorous intensity from cadence. Optimal cadence thresholds were identified using Youden’s index. The cadence-intensity relationshipwas also quantified using a segmented regression model with random coefficients. Optimal positive predictive values of candidate thresholds were assessed to determine final heuristic values.

RESULTS: Data were complete for all 80 participants(40 men, 40 women; age=50.2±5.9 years; BMI=26.0±4.0 kg/m2; height=171.0±9.2 cm). ROC cadence thresholds for moderate and vigorous intensity were 98.5 and 117.3 steps/min, respectively. All sensitivity values were over 90% and all specificity values were over 80%.The relationship between cadence and METs was explained by two distinct linear regression trends displaying a breakpoint at 97.6 steps/min. Cadence explained 78% of the overall variance in intensity. Cadence thresholds (95% Prediction Intervals) for 3 METs and 6 METs were 101.7 (54.9 -111.8) and 132.1 (122.0 -142.2) steps/min, respectively. Heuristic values for moderate and vigorous intensity were 100 and 130 steps/min, respectively.

CONCLUSIONS: Cadences of 100 and 130 steps/min are reasonableheuristic values respectively identifying moderate and vigorous intensity walking in middle-aged adults.