How many steps per day are enough? For older adults David Rowe Physical Activity for Health Research Group University of Strathclyde (Symposium with Catrine Tudor-Locke, Greet Cardon, Ilse De Bourdeaudhuij)

Standard-setting Normative data Intervention effects Range of typical steps for the population Intervention effects Reasonable expectations for change Controlled studies (cadence-time conversions) What step rate ≈ 3 METs? Computed step count equivalents Baseline steps + 30 min MVPA equivalent (from #3) Daily step-MVPA minutes equivalance (“test equating”) Regression, ROC curves Steps/day differentiating health and unhealthy populations (“known groups” evidence) Maximal separation, group significant differences

= = = = (?)

Question 1 – daily steps and minutes of MVPA Methods: Two separate waves of data collection, in 40-59 year old (n = 129) And in 60-87 yr old (n = 94) men and women Actigraph 7164 worn for 7 days, 1-min epochs Minutes of MVPA determined using Freedson equation (> 1951 cts/min) Data analysed as average daily steps/mins MVPA, and as individual days Results were similar

Regression method Middle-aged: Mins MVPA = 0.0041*steps – 15.417 [r = .61] =========================================== Older: Mins MVPA = 0.0038*steps – 15.772 [r = .70] Combined: Mins MVPA = 0.0041*steps – 16.551 [r = .67] 0 mins MVPA ≈ 4,000 steps (+ 10 mins MVPA ≈ 2,400 steps)

Error in predicting MVPA from steps

Conclusion – steps/day and MVPA Between 40 years and 90 years, daily steps are moderately-highly correlated with minutes of MVPA Age does not add to or moderate the steps-MVPA relationship In cross-sectional data, people who take more moderate-intensity PA also engage in more mins of PA below moderate intensity The relationship between steps and minutes of MVPA appears to become stronger as we age This requires confirmation in larger epidemiological data sets (e.g., NHANES)

Question 2 – cadence/walking intensity Methods: Two samples, of younger (n = 38; 20-55 yr) and older (n = 30; 60-87 yr) women Controlled laboratory study of treadmill and overground walking Data presented here are from treadmill trials Speed, cadence, METs, heart rate Three trials (slow, medium, fast) ranging from 1.5 to 4.2 mph

Speed-intensity (MET) relationship Younger: METs = 1.27225*mph – 0.0448 [r = .68] 3 METs = 2.4 mph =========================================== Older: METs = 1.103253*mph + 0.9113 [r = .56] 3 METs = 1.9 mph

Cadence-intensity (MET) relationship Younger: METs = 0.05392*steps/min – 2.4641 [r = .56] 3 METs = 102 steps/min =========================================== Older: METs = 0.04539*steps/min – 1.3082 [r = .56] 3 METs = 95 steps/min

Speed-Cadence relationship

Speed-intensity (%MXHR) relationship

Speed and EE – prior research Adapted from Martin, Rothstein, & Larish (1992) Effects of age and physical activity status on the speed-aerobic demand relationship of walking J. Appl. Physiol., 73(1), 200-206.

Conclusion – cadence and intensity Investigating the cadence/intensity relationship is complex Speed/cadence varies with age (cadence higher in older age) Treadmill vs. overground issue Intensity (METs) higher for a given speed in OAs But at a given cadence, speed is lower Net effect appears to be a slightly higher intensity (METs) for a given cadence [maybe ...] We should focus on “what cadence/intensity brings health benefits?”

But how should we interpret “moderate intensity?” 3 METs = higher relative intensity in older adults

Thank you! david.rowe@strath.ac.uk