What Happens When You Stop Working Out? A Week-By-Week Breakdown of Deconditioning
The decline is real and happens faster than you think.
You’ve been crushing it at the gym, logging miles on the treadmill, or maybe just maintaining a solid movement routine. But then—life happens. Work deadlines explode, travel gets in the way, or burnout convinces you that skipping workouts is self-care. Suddenly, it’s been a few days, then a week, then…you can’t even remember the last time you laced up your sneakers. So, what happens to your body when you stop working out? How fast do you actually lose your hard-earned gains?
Here’s the blunt truth: your body doesn’t waste time hitting the reverse button. But the speed and extent of your fitness decline depend on factors like training history, fitness level, and how long you’ve been sedentary. Let’s break it down week by week, and then month by month, extending to a full year of inactivity.
Week 1: The "I’m Fine" Phase
If you’ve been consistently active, skipping workouts for a week won’t ruin you.
In fact, a short break can be beneficial, allowing for muscle recovery and nervous system reset. You might even feel stronger when you return—if you get back on track quickly.
But beneath the surface, the first cracks in your fitness foundation are forming. Your body starts dialing down its efficiency. Studies show that VO2 max (your body’s ability to use oxygen for energy) begins to decline within 7-10 days.
It’s subtle, but your cardiovascular endurance is already slipping.
What’s happening?
Slight decrease in VO2 max (~2%)
Muscle glycogen stores start depleting, reducing endurance
Strength holds steady, but neuromuscular efficiency begins to drop
Week 2: The "Wait, Why Am I Winded?" Phase
At this point, your cardiovascular fitness takes a noticeable hit.
VO2 max can drop by 4-6%, meaning those stairs to your office suddenly feel extra annoying. Blood volume decreases, making your heart work harder to pump oxygen. The result? You get winded more easily.
Muscle-wise, you’re still holding on—but just barely. If you’ve been lifting consistently, your nervous system is the first to take a hit. You may notice your coordination feels a little off when you finally pick up the weights again.
What’s happening?
VO2 max declines by up to 6%
Blood volume drops, increasing heart rate during exertion
Strength remains mostly intact, but coordination suffers
Muscle endurance starts to decline
Week 3: The "Uh-Oh" Phase
Now, the losses start piling up.
Your cardiovascular capacity is shrinking rapidly, with VO2 max down by 8-10%. Your heart pumps less efficiently, and your aerobic endurance feels like it’s been on a crash diet.
Strength takes its first real hit here. Your muscles start losing neuromuscular adaptations, meaning movements that once felt effortless suddenly feel awkward. If your workouts involve explosive movements (sprints, Olympic lifts, HIIT), expect a noticeable decline in power.
What’s happening?
VO2 max down by 10%
Heart rate increases during workouts
Neuromuscular efficiency declines (exercises feel harder)
Small decrease in muscle mass (~1-2%)
Week 4-5: The "Where Did My Strength Go?" Phase
This is where the real damage happens.
If you’ve been out for a month, your cardiovascular fitness has dropped by 12-15%, making long workouts feel significantly harder. Blood flow to your muscles is reduced, making recovery slower.
Muscle loss (atrophy) begins in earnest now. While strength declines are still reversible, you’ll notice a 5-8% drop in muscle mass, especially if you haven’t been maintaining protein intake. Strength losses hit fast-twitch muscle fibers the hardest, meaning sprinting, jumping, and heavy lifting feel significantly more difficult.
What’s happening?
VO2 max down 12-15%
Strength declines (especially in power-based movements)
Muscle mass loss accelerates (5-8% reduction)
Insulin sensitivity drops, increasing risk of fat gain
Month 2-3: The "Time to Rebuild" Phase
At two to three months out, you’re officially in the deconditioned category.
VO2 max has declined 15-20%, and your resting heart rate is noticeably higher. Muscular atrophy is more pronounced—expect a 10% loss in muscle mass and a drop in overall strength by 10-15%.
This is also when metabolic shifts start working against you. Insulin resistance increases, making it easier to gain fat and harder to regulate blood sugar. Mentally, motivation tends to decline, creating a vicious cycle of avoidance.
What’s happening?
VO2 max down 15-20%
Strength down 10-15%
Muscle mass loss continues (10% total reduction)
Increased risk of fat gain due to metabolic slowdown
Months 4-6: The "Starting Over" Phase
After six months, your cardiovascular system has regressed significantly, and workouts that once felt easy are now daunting. Strength and muscle loss become significant (up to 20%), and bone density may also start declining, increasing injury risk.
If you've been completely inactive, metabolic rate has slowed, and body composition shifts toward increased fat storage.
What’s happening?
VO2 max down 25%+
Strength down 15-20%
Muscle loss (up to 20%)
Bone density decreases
Motivation and mental barriers become the biggest challenge
Months 7-12: The "Distant Memory" Phase
By the time you hit a year of inactivity, your fitness resembles that of a sedentary person.
Your cardiovascular endurance is back to baseline, muscle mass has declined 30% or more, and overall metabolic efficiency is compromised. If you were highly trained before, the losses will be less severe, but regaining fitness will take significant time and effort.
What’s happening?
VO2 max drops 30-40%
Strength and power drastically reduced
Muscle mass loss reaches 30% or more
Bone density loss increases fracture risk
Energy levels and motivation to exercise are at an all-time low
How to Minimize Damage & Get Back Faster
Even if you’re slammed with work, you don’t have to lose everything. Here’s how to soften the blow:
Do something – Even 10-15 minutes of movement a few times a week helps maintain neuromuscular function.
Prioritize strength – Muscle is harder to regain than cardio. Strength train at least once a week if possible.
Stay active in daily life – Walk, take the stairs, stretch. Small movements add up.
Ease back in strategically – Don’t go from zero to 100. Start with lighter loads and lower intensity to avoid injury.
Final Thoughts
Stopping exercise isn’t an instant death sentence for your fitness, but the decline is real—and it happens faster than you think. The good news? Your body wants to be strong. With the right approach, you can regain what you’ve lost. Just don’t wait too long to get back in the game.
So, if you’ve been on an accidental hiatus, consider this your sign: it’s time to move again. Your future self will thank you.
Article References
The sources cited in the article:
Men’s Journal. "What Really Happens When You Stop Working Out." Men’s Journal - When You Stop Working Out
University of Michigan Medicine (UM) “What Happens to Your Body When You Stop Exercising.” UM - When You Stop Exercising
Runner’s World (RW). “How Fast Do You Lose Fitness When You Take a Break From Running?” RW - Lose Fitness Take a Break
Forbes. "Feeling Stuck? A 3-Step Guide to Get Unstuck and Move Forward." Forbes - Feeling Stuck? How to Move Forward
The NYTimes. “Feeling Stuck? 5 Ways to Jumpstart Your Life.” NYT - Feeling Stuck? 5 Ways to Jumpstart Your Life