Time To Missed Exercise Farrokh Alemi, Ph.D.

Why do it? You need to distinguish between random days of missed exercise from real changes in underlying exercise patterns You need to distinguish between random days of missed exercise from real changes in underlying exercise patterns

Steps in construction of days of missed exercise 1. Verify assumptions 2. Collect data 3. Calculate time to failure 4. Calculate control limits 5. Plot chart 6. Interpret findings 7. Display chart

Step 1: Check assumptions One observation per day One observation per day Everyday is a new day. Everyday is a new day. Exercise on one day does not affect exercise on other days Exercise on one day does not affect exercise on other days Successes are more frequent than failures Successes are more frequent than failures Longer stretches of missed exercise are more rare Longer stretches of missed exercise are more rare

Step 2: Collect data Decide what is your exercise plan Decide what is your exercise plan Keep a diary Keep a diary Record for each day if you kept to your plans Record for each day if you kept to your plans Keep notes of major changes in your life style Keep notes of major changes in your life style

Step 3: Calculate length of missed plans

Step 4: Calculate control limits R is the ratio of failure days to success days R is the ratio of failure days to success days UCL = R + 3 [R * (1+R)] 0.5 UCL = R + 3 [R * (1+R)] 0.5

Step 5: Plot control chart X-axis is time X-axis is time Y-axis is either length of failures Y-axis is either length of failures UCL is drawn as straight line UCL is drawn as straight line

Steps 6 & 7: Interpret findings & display chart Any series of failures exceeding UCL cannot be due to chance. Any series of failures exceeding UCL cannot be due to chance. It is a real change in exercise patterns It is a real change in exercise patterns Display chart Display chart For yourself For yourself For others For others

Example 35 year old female kept daily record of keeping to exercise plans for 18 days 35 year old female kept daily record of keeping to exercise plans for 18 days First week was pre-intervention First week was pre-intervention Failures occurred on 2 nd to 4 th, 6 th, 7 th and 16 th day Failures occurred on 2 nd to 4 th, 6 th, 7 th and 16 th day Is she improving? Is she improving?

Calculate length of failures Set to 0 every time we succeed Set to 0 every time we succeed Set to one on first day of failure Set to one on first day of failure Increased when more than one consecutive day of failure Increased when more than one consecutive day of failure

Calculate ratio for post intervention period Number of days of failure Number of days of success Ratio = 1 days 10 days =.10

Calculate upper control limit UCL= Ratio + 3 * (Ratio*(1+Ratio)).5 UCL = * (.1*(1.1)).5 = 1.09

Plot chart

Interpret findings & display Lots of long failures before the intervention Lots of long failures before the intervention No significant failures since the intervention No significant failures since the intervention