Capability vs capacity. Similar words with very different meanings. A concept I hadn’t thought about until this past July when I saw a video of a woman explaining the difference. It has been something I can’t “unhear” and it has been on my mind ever since. First, let me rewind my story to give the background of why this concept hit so hard.
My Half Marathon: Capability vs Capacity in Real Life
This past May, I completed a half marathon.
In 2024 and 2025, I had taken somewhat of a hiatus from running while other areas of life took priority. So when I saw that there was a half marathon in a neighboring town that landed on my 30th birthday, I thought it was just meant to be!
I had completed the half marathon distance before, so when I signed up, I was mostly just excited with very little nerves. I was excited to have a goal to train for and a finish line to cross. Remember, at this point, the concept of capability vs capacity was not on my radar.
Years ago, I was managing nursing school, working, and running 30+ miles a week. Surely I was capable of doing this again, right? Technically, yes. But that was where I was missing an important piece of the puzzle. I was confusing my capability with my capacity.
I definitely did my best to prioritize running and follow my training plan. Every Sunday, I dedicated the day to my long runs. I even hired a nutritionist to make sure I had a fueling plan to help me succeed.
So needless to say, I was extremely disappointed when race day came and it was quite literally my worst running experience ever. It wasn’t just that I didn’t hit the time I wanted, or my legs felt tired. It was a deeper feeling of disappointment. I walked away thinking, I did the best I could in the moment, but my body did not perform how I know it can.
Why Capability vs Capacity Matters
So, what is the difference between capability vs capacity? Your capability is what you are physically, mentally, or technically able to do. Your capacity is what you realistically have the resources to do at a particular point in time.
Think of it like this; your car has the capability to drive 2500 miles. But without filling it with gas, and changing the oil, it does not have the capacity to perform how it should.
Your capability might be running a half marathon in two hours. Your capacity might only allow you to train for one in a way that gets you across the finish line feeling strong and healthy. Those two things aren’t necessarily the same.
I was expecting myself to perform as if I was in the same situation, with the same capacity to train, as I had years ago. But my life wasn’t the same. Back then, I didn’t have a house to maintain, two dogs, jobs where I was working more than 40 hours a week, or the workload of helping my husband build a house. Those things aren’t excuses, they are simply realities.
My life had changed, and therefore, my capacity had changed. I was still capable of training for and completing a half marathon. But I didn’t have the same capacity to dedicate to that goal that I had years ago. And I think this distinction is incredibly important when we talk about goals.
Capability vs Capacity in Training
As athletes, we tend to focus heavily on capability. Questions like:
How much can I lift? Run? Hike?
What have I done before? What am I capable of?
Those questions aren’t necessarily bad. In fact, knowing what you’re capable of can be incredibly motivating. The problem happens when we assume that because we can do something, we should always be able to do it. Training doesn’t happen independently from the rest of your life.
Your recovery, sleep, stress, nutrition, work, relationships, responsibilities, and mental energy all contribute to your overall capacity. You might be capable of training five or six days a week. But do you have the capacity to do that right now? You might be capable of running 30 miles a week. But can your current life support 30 miles a week without leaving you exhausted? You might be capable of lifting heavier weights. But if you’re already overwhelmed, stressed, and under-recovered, is pushing for more actually the best choice?
These are two very different questions.
How Capability vs Capacity Rewired My Brain
I’m not going to lie, after the race I did get pretty down on myself. I was so pumped for this run that the disappointment of not doing what I knew was my best really shook me.
I followed my training plan, yes. But in doing so, I put my body under so much stress that everything in life became harder. The weeks leading up to the race, I couldn’t wait for it to be over.
I wanted the training to be over, the stress to be over and I just wanted to feel like myself again. Looking back, I can see that as a pretty significant warning sign. I was so focused on what I knew I was capable of that I ignored what I actually had the capacity to handle.
I started in the dangerous cycle of thinking I didn’t train hard enough, I need to try harder. Worst of all, thinking I failed.
Instead of being proud of myself and recovery after the previous 12 week training block, I immediately jumped into lifting heavier and training harder. All to prove to myself that I am still capable of everything I was all those years ago. I felt like I was on a spinning wheel, trying so hard but failing harder. In June & July, my mental health plummeted. I didn’t know what to do. For the past 7 years running, fitness, movement has always been the thing that kept me mentally healthy. Now, it was starting to feel like it was destroying my mental well-being. I was worried that if I back off of running, training and movement, that I would lose these aspects of my personality altogether. I wasn’t ready for that.
Your Capacity Isn’t Fixed
As any type-A perfectionist knows, changing these thoughts does not happen overnight. Just because I saw a 90 second video explaining capability vs capacity doesn’t mean I don’t still have thoughts of always needing to do better. But since understanding this concept, I am able to remind myself that just because I don’t have the capacity now, doesn’t mean I won’t ever again.
That is one of the most important things I’ve taken away from this is that capacity changes. Your capability may remain relatively consistent, but your capacity can fluctuate dramatically depending on what’s happening in your life. Capacity isn’t a measure of your worth, your discipline, or your fitness level. It’s simply a reflection of what you can realistically support right now.
Over the past few months my movement has been focused on doing things that make me feel strong and confident. Just this week I went on my first run since the half marathon. I had zero expectations or goals. I ran just because I wanted to.
Stop Using Your Best Season as the Standard for Every Season
I don’t regret doing the half marathon. Though I didn’t have the outcome I expected, I did experience a great life lesson. We often compare our current selves to a previous version of ourselves.
Maybe you used to run five days a week, or used to lift heavier. Just because you’ve done it before, you assume you should be able to do it again.
But what if life isn’t the same? You don’t have to earn the right to change your goals simply because you’ve accomplished something before. Your previous best doesn’t have to become your current minimum.
Movement should add to your life, not make everything else seem unmanageable. There’s a difference between challenging yourself and constantly operating beyond what you can sustainably handle. A good goal should challenge you without consuming you. So instead, consider asking:
What is my life asking of me right now?
What do I realistically have the capacity to do?
Is there a level of training that allows me to make progress without making everything else in my life harder?
This doesn’t mean you choose the easiest goal. The long term goal can still be the same. But if you don’t have the capacity to accomplish this goal right now, you set shorter goals in the meantime until you get there. Sometimes the smartest thing you can do for a goal is give yourself more time.
What I’m taking forward
My half marathon experience taught me that following a training plan doesn’t automatically mean the plan is right for you at that moment. You can do everything “right” on paper and still find that the goal isn’t working with your current life. Despite negative thoughts telling me otherwise, this doesn’t make me lazy and it doesn’t mean I’m losing fitness. It certainly doesn’t erase everything I’ve accomplished before. What it means is I’m a human being with circumstances that have changed.
Your capacity will change throughout your life. There will be seasons where you can train hard, chase big goals, and push your limits. There will also be seasons where maintaining your fitness, getting outside, moving your body, and taking care of yourself is the goal.
All the seasons matter. And none of them determines your worth as an athlete.