Why Your Sore Tendon Needs Load, Not Rest

If you’ve ever felt that deep, nagging ache in the back of your heel, the one that’s stiff and sore for the first few steps out of bed and then warms up once you get going, you’ve met tendinopathy. And if your instinct was to stop, rest it, and wait for it to heal, I understand why. It’s also the single most common mistake I see athletes make.

I have worked through tendinopathy myself and completely resting it, will do NOTHING to heal a tendon.  Careful and progressive loading is what the tendon actually needs to rebuild. Here’s why, and how to think about it.

Rest Feels Right. It Also Doesn’t Work.

A muscle strain and a cranky tendon are different problems. When you rest a tendon completely, it doesn’t come back stronger. It gets less capable. The tendon loses the very capacity you need to run pain-free, so when you return to training, the same loads that irritated it before now land on a weaker structure. You feel better for two weeks off, then you’re right back where you started within days of running again. Sound familiar?

Tendons are living tissue that adapts to the demands you place on them. Take the demand away entirely and they detune. The fix for an under-capacity tendon isn’t less load. It’s the right load, applied in the right order.

How Load Actually Repairs a Tendon

Tendons respond to mechanical loading by remodeling. When you load a tendon in a controlled, progressive way, you stimulate the cells inside it to reorganize and build, gradually increasing the tendon’s stiffness and its ability to store and return energy. Over weeks and months, that’s what raises your pain threshold and your performance ceiling at the same time.

The keyword is progressive. You’re not trying to blast the tendon or push through sharp pain. You’re giving it a reason to adapt, then a slightly bigger reason, then a bigger one, staying just ahead of where it is without overwhelming it. Think of it the way you’d build mileage: you don’t jump from 20 to 50 miles a week, and you don’t fix a tendon by going from zero to plyometrics.

The Loading Ladder

Rehab research generally moves a tendon through stages, from least demanding to most. You climb the ladder as pain and capacity allow.

Rung one: isometrics. These are holds. You contract the muscle and load the tendon without any movement at the joint, like rising onto your toes and holding, or pushing against something that doesn’t move. This is the smart on-ramp when a tendon is irritable, because you can load it meaningfully without the stretch-and-shorten cycle that tends to aggravate it early on. You get to start building capacity right away instead of waiting.

Rung two: heavy slow resistance. Once you tolerate holds, you progress to slow, heavy, full-range strength work, calf raises through their full range with real load, moving slowly up and down. This is where a lot of the meaningful tendon remodeling happens, and the evidence base here is strong.

Rung three: energy storage and release. The final rungs reintroduce speed and spring, hops, bounding, and eventually the running-specific loads your sport demands. This is where the tendon relearns to act like the spring it’s supposed to be. You don’t get here first. You earn it.

A Straight Answer About Isometrics

Isometrics got popular a few years ago on the back of a widely shared finding: a 2015 study of athletes with patellar (knee) tendon pain found that isometric holds produced a large, immediate drop in pain.1 That’s a real result, and it’s why you’ll hear coaches talk about isometrics as a pain-relief tool you can use even in-season.

But here’s the honest part, and it matters because so many of you are dealing with the Achilles specifically. When researchers tested that same immediate pain-relief effect in people with mid-portion Achilles tendinopathy, they didn’t find it. In a trial of 91 patients, isometric calf holds produced no meaningful immediate pain relief compared to other approaches, or even to rest.2 The dramatic painkiller effect that made isometrics famous shows up more reliably in the patellar tendon than in the Achilles.

So don’t do your isometric holds expecting the ache to vanish on the spot. That’s not why they’re on the ladder. They’re there because they let you start loading a grumpy tendon safely and begin rebuilding capacity from day one. The pain relief, when it comes, comes from the weeks of progressive loading that follow, not from a magic hold.

That distinction is the whole point of doing this honestly. Isometrics are the on-ramp, not the destination.

Let the Tendon Tell You Where You Are

The reason I don’t hand athletes a rigid day-by-day tendon protocol is that tendons don’t read calendars. They respond to load, and the tendon itself gives you the feedback you need if you’re paying attention. Two rules I coach:

Use a pain scale, and stay in the acceptable range. Some discomfort during loading is okay for a tendon; sharp or climbing pain is not. A common guideline is to keep pain at a low, tolerable level during and right after the work, not pushing into the range where you’re wincing.

Judge by the next morning. The real test isn’t how it feels during the exercise, it’s how the tendon responds over the next 24 hours. If it’s calmer or the same the next morning, the load was appropriate. If it’s noticeably more irritated and stiff, you asked for too much, and you scale back the next session. That morning check-in is your traffic light: green to progress, yellow to hold steady, red to back off.

This is exactly how I’m managing my own Achilles. I’ve been using an AlterG anti-gravity treadmill to control the load precisely, dialing body weight up as the tendon earns it, and reading that next-morning response to decide each day’s dose rather than forcing a predetermined plan. Progressive, responsive, patient. That’s the game.

The Bottom Line

Your sore tendon isn’t asking you to stop. It’s asking you to load it intelligently: start with holds to get on the ramp, build through heavy slow strength, and earn your way back to speed, all while letting the tendon’s day-to-day response set your pace.

Rest might quiet the pain for a week. Load is what rebuilds the tendon. Respect the difference, climb the ladder in order, and you come back not just healed, but harder to break next time.

Dealing with a nagging Achilles or a cranky tendon and not sure how to load it? That’s exactly the kind of thing our coaching is built for. Reach out and let’s build you a plan that fits where your tendon actually is.

This article is educational and reflects current research on tendon rehabilitation; it isn’t a substitute for individualized assessment. If you have persistent or worsening tendon pain, get evaluated by a physical therapist or sports medicine professional.

Footnotes

  1. Rio, E., Kidgell, D., Purdam, C., Gaida, J., Moseley, G. L., Pearce, A. J., & Cook, J. (2015). Isometric exercise induces analgesia and reduces inhibition in patellar tendinopathy. British Journal of Sports Medicine, 49(19), 1277–1283. ↩

  2. van der Vlist, A. C., van Veldhoven, P. L. J., van Oosterom, R. F., Verhaar, J. A. N., & de Vos, R. J. (2020). Isometric exercises do not provide immediate pain relief in Achilles tendinopathy: A quasi-randomized clinical trial. Scandinavian Journal of Medicine & Science in Sports, 30(9), 1712–1721. ↩

Your AI Training Plan Is Not Your Coach. Here’s Why That Matters.

By Tom Clifford | Without Limits 

Let’s start with something you probably didn’t expect to read on a coaching website: I used AI to help write this blog post.

I know. Stay with me.

Because here’s the thing, AI is genuinely useful. It can research, organize, draft, and produce content faster than any human. I’m not here to tell you technology is bad. I coach athletes for a living. I know that tools matter.

But there’s a difference between a tool and a coach. And right now, a lot of runners and triathletes are confusing the two, and paying for it on race day.

The App Told Me to Run 8 Miles. So I Did.

Your AI training plan doesn’t know that your left knee has been talking to you for three weeks. It doesn’t know you had a terrible night’s sleep because your kid was sick. It doesn’t know the humidity hit 90% this morning and your “easy 8 miles” just became a survival march.

It just said 8 miles. So you ran 8 miles. And now your knee is angry.

I’ve been running for 32 years. I’ve seen this pattern hundreds of times. The athlete who follows the plan perfectly,  and breaks down because the plan didn’t know them.

An algorithm can build a plan. It cannot read your face when you show up to group training at 5:30am looking like you haven’t slept in three days. I can. And I will absolutely modify your morning around that, because I know the difference between an athlete who needs to be pushed and an athlete who needs to be managed.

That’s not something a language model learns from your heart rate data.

What 32 Years in the Sport Gives You

I ran my first race in 1993. I’ve trained through heat, snow, woke up at 5am in 2 degree temps, hurricanes, injuries, bad seasons, great seasons, and one memorable 50K.

In those 32 years, I’ve learned things that don’t exist in any database. I know what a runner looks like when they’re about to hit a wall three miles before they think they will. I know when an athlete says “I feel fine” and means it, versus when they say “I feel fine” and are lying to themselves. I know which athletes train great alone but fall apart in race environments — and how to fix that.

You cannot compress 32 years of real experience into a training plan prompt. You can’t ask ChatGPT “what does a runner look like six weeks before they quit?” and get an answer that’s worth anything.

Experience isn’t data. It’s pattern recognition built from being there, in person, in conditions, in the real world — over and over and over again.

The Group Is the Secret Weapon

Here’s what no app is giving you: the energy of 30-60 people showing up at 5:30am.

When you train alone with a plan on your phone, motivation is entirely on you. Some days that works. Most days,  if we’re being honest, it doesn’t. You negotiate with yourself. You shorten the run. You skip the tempo intervals.

In a group, something different happens. The person next to you is going. So you go. The pace picks up. You find something you didn’t know you had. You finish a workout you would have quit at mile 2 if you were alone on a treadmill.

That dynamic is not replicated by any app, any algorithm, or any AI. It is a human thing. It requires human beings in the same space, at the same time, suffering and succeeding together.

Motivation delivered through a push notification is not motivation. Motivation is your training partner refusing to let you slow down with 400 meters left.

I’ve watched athletes nail every workout in their training plan and then fall completely apart in a real race environment. You want to know why?

Because they trained in a controlled environment and expected race day to be controlled.

It isn’t.

Race day is humidity and headwinds and a porta-potty line that cost you four minutes and a nutrition strategy that stopped working at mile 9. Race day is the athlete who goes out too fast in the first mile and blows up by mile 6, because no one ever taught them what controlled effort actually feels like in a crowded race start.

When I coach athletes onsite, I teach them to train in the real world, in real conditions, with real obstacles, with real people around them. We run the hills that hurt. We do brick workouts in heat when it would be easier to reschedule. We practice start-line strategy because the start line is where bad decisions are made most often.

A training plan tells you what to do. A coach teaches you how.

The Collaboration Nobody Talks About

Here’s the part that gets left out of every “AI vs. human” conversation:

The best coaching relationships are collaborations.

When I build a plan for an athlete, I’m not handing down commandments. I’m starting a conversation. How did that feel? What’s your body telling you? What happened at work this week? Are we being realistic about this timeline?

That back-and-forth,  the athlete’s honest self-reporting, my experience interpreting it, and the ongoing adjustment of the plan, that is where results come from. Not from the plan itself. From the process of building it together, in real time, with a human being who gives a damn whether you make it to the finish line.

So Where Does AI Fit?

I’ll be straight with you: I use AI tools to make my coaching better. I use them to organize, to research, to communicate faster with athletes, to help produce content like this. Technology makes me more efficient.

But efficiency is not coaching. Efficiency is infrastructure.

The coaching is me, on the track at 5:30am, watching how you’re moving, adjusting your effort, pushing you past what you thought was your limit, and celebrating with you when you cross a finish line you weren’t sure you could reach.

Thirty-two years of that. No app included.

The Bottom Line

Use the apps. Track your data. Listen to the podcasts. Read the blogs. I’m not against any of it.

But if you’re serious about your running or triathlon, if you have a real goal and a real timeline and you actually want to get there, hire a coach. A real one. One who’s been where you are, has seen what you’re going through, and will be standing there at the track when the plan says easy day but your body says otherwise.

Success in endurance sports doesn’t come from the perfect algorithm. It comes from collaboration between an athlete who shows up and a coach who knows what to do with them when they do.

The work is still the work.

Do the work.

— Tom

Tom Clifford is the CEO of Without Limits Endurance and a USATF Level 2 and USA Triathlon certified coach with 32 years of running experience. He coaches runners and triathletes of all levels across the Carolinas — in person, in groups, in the real world.

Ready to stop training alone? Learn more about coaching programs at Without Limits.

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