Where the numbers come from

The American Heart Association guideline

The AHA recommends at least 150 minutes a week of moderate-intensity aerobic activity, or 75 minutes of vigorous activity, or an equivalent mix, preferably spread through the week; muscle-strengthening on at least 2 days; and notes additional benefit from being active 300 minutes a week or more.

CtrlAltMove scores this with activity points: one point per moderate minute, two per vigorous minute. 150 points a week is the guideline; 300 is the extra-benefit range. "Moderate" and "vigorous" follow the standard intensity bands (3.0–5.9 and 6.0+ METs, or the matching heart-rate zones when the app can measure them). Strength days count only when the app verified the session at a gym — nothing is taken on the honour system.

• American Heart Association — Recommendations for Physical Activity in Adults
• Ainsworth BE et al. 2011 Compendium of Physical Activities — the MET values assigned to each kind of movement and intensity.

"Extra months of life"

The curve comes from the largest pooled analysis of leisure-time activity and mortality:

• Moore SC et al. Leisure Time Physical Activity of Moderate to Vigorous Intensity and Mortality: A Large Pooled Cohort Analysis. PLoS Medicine, 2012. Six prospective US cohorts, 654,827 adults aged 21–90, 82,465 deaths, a median of 10 years of follow-up. Table 3 reports years of life gained after age 40 by MET-hours of activity per week, relative to none: about 1.8 years for even a little, 2.5 for a little more, 3.4 at the guideline, 4.2 above it, and 4.5 at the top.
• Arem H et al. Leisure Time Physical Activity and Mortality: A Detailed Pooled Analysis of the Dose-Response Relationship. JAMA Internal Medicine, 2015. 661,137 adults, 116,686 deaths. Confirms the shape: most of the benefit arrives by the guideline, the curve plateaus at three to five times it, and there is no excess risk at ten times it. This is why the app never shows more than 4.5 years, however much you plan.

The arithmetic

1. Each planned movement contributes minutes × MET ÷ 60 MET-hours, counting only moderate-or-harder movement (3.0 METs and up), as the studies did.
2. The week's MET-hours are placed on Moore's curve, interpolated between the midpoints of the study's bands and capped at 4.5 years.
3. Below one MET-hour a week — about fifteen minutes of brisk walking — the app says "too little to estimate" instead of a number. The study's lowest band is wide, and a straight line from zero would show months for minutes.
4. Age shapes the figure: the years at 40 are the study's own, and for older ages the app scales them by how the same reduction in mortality plays out later in life, using a standard mortality model fitted to the US life table. The decline is gentle — a 70-year-old keeps most of the age-40 figure. Under 40, the age-40 figure is shown.
5. The result is rounded to whole months and labelled "if you kept a week like this from here on, compared with not exercising at all".

What it does not account for

• Your current fitness or activity. The comparison is with no activity; someone already active gains less than the number by switching to a given plan.
• Your medical history, sex, weight, smoking, diet, sleep, or anything else that shapes a life. The studies adjusted for many of these on average; the app knows none of them.
• Whether the plan is actually kept. The figure assumes the week is repeated for the rest of your life.
• Cause and effect. These are observational cohorts: they show association, adjusted as carefully as the authors could, not a controlled experiment.

In one line

It is our best effort at an honest statistical estimate, drawn from the best available evidence, shown to help you weigh a week — and it will not match your lifespan, your health, or your benefit from exercise to the letter. Mileage may vary.

Deposit contracts

The optional stake — your own money, lost only if you skip a workout you planned — rests on two trials:

• Royer H, Stehr M, Sydnor J. Incentives, Commitments, and Habit Formation in Exercise: Evidence from a Field Experiment with Workers at a Fortune-500 Company. American Economic Journal: Applied Economics, 2015. Employees were paid to visit the company gym for a month, then offered a self-funded commitment contract: their own money, forfeited to charity if they stopped going. Among those who took the contract, about 47% of the attendance gain was still there years later, against about 16% for those who had only been paid. It is the one intervention in this literature with a multi-year effect.
• Halpern SD et al. Randomized Trial of Four Financial-Incentive Programs for Smoking Cessation. New England Journal of Medicine, 2015. The cleanest deposit trial, in smoking rather than exercise. In the trial's instrumental-variable analysis, among the people who would accept a deposit, deposit programmes raised sustained abstinence at six months by 13.2 percentage points over reward-only programmes (95% CI 3.1 to 22.8). Only about 13.7% of people offered a deposit accepted one — a minority taste, and the minority who choose it get the effect.
• Why it works, in one line: loss aversion. A loss of a given size weighs roughly twice as much as a gain of the same size (Kahneman D, Tversky A. Prospect Theory: An Analysis of Decision under Risk. Econometrica, 1979), and a cost you set for yourself in a calm moment binds the tired one.

What we do not claim. Neither study used an enforcement lock, and neither measured what CtrlAltMove measures — kept deadlines per week. Both are the best available prior for a stake on a lock, not a measurement of one. We report our own outcome as it comes in, and the numbers above are a compass, not a promise. Mileage may vary.

Questions

If you think a number is wrong, or a source is misread, write to support@ctrlaltmove.com. We would rather correct it than defend it.