The Minimum Effective Dose: How Little Exercise Do You Actually Need?

I'm going to say something that surprises most people:

More is not always better when it comes to exercise.

After a certain threshold — one that's lower than most fitness culture would have you believe — additional volume stops producing proportional benefits and can actually begin to increase inflammatory load, injury risk, and overtraining stress.

This isn't a license for couch living. It's a case for intelligent movement — understanding the research on minimum effective doses and applying it so that you build a sustainable, health-promoting practice without burning out or injuring yourself in the attempt.

What the Research Actually Shows

A landmark study published in JAMA Internal Medicine followed 650,000 adults and found that the majority of mortality risk reduction from exercise occurred within the first 150 minutes per week of moderate activity. Going from zero to 150 minutes reduced mortality risk by 31%.

The next 150 minutes (300 total per week) added only an additional 3–4% reduction.

Beyond that, the curve flattens dramatically.

This doesn't mean stop at 150 minutes. If you love exercise and your recovery supports more volume, keep going. But it does mean: if your life is genuinely constrained and you can only do 30 minutes a day, five days a week — you are capturing the overwhelming majority of the health benefit available to you.

You don't need to be an athlete to be healthy. You need to be consistently, reliably active.

High-Intensity Interval Training: Maximum Return on Time

For people with limited time, HIIT (High-Intensity Interval Training) is the most researched and validated protocol for health benefit per minute invested.

A 2016 study in PLOS ONE from McMaster University found that 3 sessions of 10-minute HIIT workouts per week (with only 1 minute of truly hard effort within each session) produced cardiovascular and metabolic adaptations similar to 150 minutes of continuous moderate exercise per week.

Total vigorous exercise: 3 minutes per week.

Now — this was a study on previously sedentary adults over 12 weeks, and long-term health maintenance likely requires more than this extreme minimum. But the principle is powerful: brief, intense effort is metabolically and cardiovascularly potent in a way that long, slow effort is not.

A practical HIIT protocol requires no equipment:

1. Warm up for 3 minutes (light jogging in place or brisk walking)
2. Go hard for 20–30 seconds (sprint, burpees, jump rope, cycling at maximum effort)
3. Rest or go very easy for 90 seconds – 2 minutes
4. Repeat 6–8 times
5. Cool down for 2–3 minutes

Total time: 20 minutes. Three times per week. That's it.

Resistance Training: The Non-Negotiable Minimum

For preserving muscle mass, bone density, and metabolic health — especially after age 40 — two sessions of resistance training per week is the evidence-based minimum.

Two sessions. That's 100 minutes a week if each session is 50 minutes long — which is more than adequate for a beginner or intermediate.

A simple two-day protocol covering all major muscle groups:

Day A (Push + Core):

• Push-ups (or bench press)
• Overhead press
• Tricep dips
• Plank variations

Day B (Pull + Legs):

• Rows (bent-over, cable, or band)
• Deadlifts or Romanian deadlifts
• Squats or goblet squats
• Glute bridges

Two days. Four exercises each. Three sets. Progressive load added when you can complete all reps with good form.

Done consistently for 12 months, this protocol produces meaningful increases in muscle mass, strength, bone density, insulin sensitivity, and resting metabolic rate.

Your Action Plan

You don't need to live in a gym. You need to:

1. Walk 7,000–10,000 steps per day (a proxy for general movement — it requires no dedicated workout time if you restructure some daily habits)
2. Two to three sessions of cardio per week (including HIIT or brisk walking)
3. Two sessions of resistance training per week

That's your minimum effective dose. That's the baseline that most clearly separates those who thrive physically into their 70s, 80s, and 90s from those who don't.

Begin there. Add from there when life allows and energy permits.

But always — always — protect the minimum.

— Dr. Lemmon