What is it
What is Mass in Motion?
Mass in Motion is a training and nutrition app for people who lift and run. It builds one weekly plan for both, scores how recovered you are each day, tracks the food that fuels it, and adjusts as your fatigue and fitness change. It isn't a step counter, and it isn't an AI chatbot in a fitness skin.
The problem it solves
If you train for strength and endurance at the same time, the hard part isn't any single workout. It's making the week add up. Running affects your legs. Heavy lifting affects your runs. Sleep, soreness, and life stress move both around. Most apps only see one side of that, so you end up guessing at the rest. Mass in Motion is built to hold the whole picture and tell you what to do next.
What's inside
Programming that fits your goal
Tell it whether you're chasing a race, more strength, both at once, or leaning out (plus your schedule, equipment, and current mileage) and it writes a plan to match. Strength work covers traditional strength, hypertrophy, conjugate-style, and powerbuilding: each with proper progressions, tapers, and deloads. Running paces come from your own recent fitness.
Logging that fits a real gym
Track lifting sets by reps in reserve and log runs by GPS or by hand. Everything saves offline first, so a bad signal or an app restart never costs you a session.
A recovery engine, not just a number
The app tracks different kinds of fatigue (systemic, muscular, and neuromuscular) and pulls in training load trends plus data from Apple Health, Strava, and WHOOP to tell you how ready you actually are.
Nutrition that closes the loop
A food logger with barcode scanning, database search, recipes, and custom foods feeds an adaptive calorie engine: it computes your observed energy expenditure from logged intake and your bodyweight trend, then steps your calorie and macro targets toward your goal each week (cut, maintain, or gain) with conservative caps and floors. One more app you don't need separately.
How it's built
A few rules it sticks to:
- Lifting effort is measured by reps in reserve, not RPE.
- No language model writes your coaching. It runs on defined training rules, your inputs, and tested logic.
- Missing wearable data doesn't break it: the recovery engine still works off your logs, it just lowers its confidence.
- It won't stack a hard, leg-heavy lift and a hard run on top of each other.
Free or Premium
Logging your own training is free. Premium adds the programming, recovery scoring, pace targets, nutrition tracking, and progress tracking: one subscription for all of it. The pricing page lays out exactly what's in each, and how it works goes under the hood.