NBA ATHLETES ARE TRAINING THEIR ACHILLES WRONG

It happened again.

79 seconds into Game 4 of the 2026 playoffs, Donte DiVincenzo planted his foot, crumpled to the floor without anyone touching him, and grabbed his lower leg. His coach Chris Finch rushed over. The arena went quiet. Everyone in the building already knew what it was before the diagnosis came.

Torn Achilles. Season over.

Fourth one in two straight playoffs. The year before it was Lillard in the first round. Then Tatum in the second round. Then Haliburton in Game 7 of the NBA Finals, with 4:55 left in the first quarter. Now DiVincenzo. Same tendon. Same no-contact collapse. Same devastated look on the floor.

The NBA commissioner convened a panel of experts. The league started feeding game film into AI looking for patterns. A University of Delaware professor named Karin Gravare Silbernagel said something that should have ended the conversation immediately: the lower leg is lagging behind everything else these athletes are doing.

But here is what the film review already showed, if anyone was paying attention. Researchers who went back through NBA Achilles rupture footage all the way to Dominique Wilkins in 1992 found the same thing every single time. One hundred percent of the ruptures involved a false step. Low center of mass velocity. The athlete stepping backward to project forward. Dorsiflexed ankle, knee extending, hip extending, trunk rotating forward. Over 80% had the foot externally rotated with a pronation moment at the bottom of that dorsiflexion. Same position. Same mechanism. Thirty-plus years of film. Not one exception.

This is not bad luck. This is a predictable mechanical event happening to tissue that was never trained to handle it.

I know a small version of what that feels like.

I was 18 years old, senior year of high school football, and I pulled my hamstring sprinting during practice. I was not going to the NFL. It was not a career-defining moment. But I sat on that field and felt the season slipping. A whole year of work. A whole team counting on you. Your body quitting at the worst possible time. It was one of the worst feelings I have ever had.

I cannot imagine what Haliburton felt with 4:55 left in the first quarter of Game 7 of the NBA Finals. I cannot imagine what Tatum felt. I do not want to imagine it. And I do not want any athlete at any level to sit on a floor and feel that.

That is why I am obsessive about this. Not because I enjoy writing about tendon biology. Because when you read the research, the answer is sitting right there and nobody is acting on it. If you want a stronger Achilles, you have to train it at its longest length. The only way to get into that position is with a steep slant board. That position, heel dropped, toes elevated, ankle fully dorsiflexed, is the same position the false step puts you in when the tendon tears. Get strong there and you are building the tissue exactly where it needs to be built. Avoid it and you are leaving the most important position untrained.

That is the whole article. Everything below is just the research that backs it up.

How the Achilles Tendon Actually Works

Most people treat the Achilles like it is just the bottom end of the calf muscle. Pull the calf, the Achilles moves. Strengthen the calf, the Achilles gets stronger. That logic seems reasonable. It is also wrong, and that wrongness is why the tears keep happening.

A tendon connects compliant muscle to stiff bone. Its entire job is force transmission, taking the pulling force the muscle generates and delivering it to the skeleton. For that to work efficiently, the tendon needs to be stiff enough to transmit force without absorbing too much of it. Think of a rope versus a rubber band attached to a rock. The rubber band stretches and absorbs the pull. The rope transfers it. A tendon is supposed to be the rope.

But here is the thing about tendons that changes everything: if you do not load them, they do not maintain that stiffness. A tendon that is not being stressed under appropriate load does not hold its properties. It degrades. The collagen inside it, organized type 1 collagen, aligned like trees in a row, high tensile capacity, starts to be replaced by disorganized type 3 collagen. Immature. Wavy. Unable to handle the same forces. The structural integrity quietly deteriorates while the muscle around it keeps getting stronger.

You need to load a tendon or else it forgets it is a tendon.

Now layer in what the Achilles is actually asked to absorb during sport. During steady state running the soleus generates roughly 7 to 8 times bodyweight of force with every stride. During acceleration phases that goes up to 10 times bodyweight. The gastrocnemius adds another 3 to 6 times bodyweight depending on speed. The Achilles is absorbing combined forces that dwarf anything most people train with. A bodyweight calf raise on flat ground is not even in the same conversation as what the tendon handles during a single hard step on a basketball court.

So you have a tissue that degrades if undertrained, absorbs enormous forces in sport, and needs specific mechanical strain to adapt. And the standard approach to training it involves flat ground calf raises that produce almost none of that strain. The gap between what the muscle can generate and what the tendon can handle quietly widens over months and years. Then someone plants for a false step in Game 4 and the tendon cannot manage the load.

That is the whole story. Everything else in this article is just filling in the details.

Why Standard Calf Training Does Not Strengthen the Achilles Tendon

Muscle and tendon adapt through different mechanisms. Muscle responds to both mechanical and metabolic stress. Get a pump, feel the burn, create enough tension, the muscle grows. Tendon does not work that way. Tendon responds to one thing: mechanical strain. Actual physical elongation of the collagen fibers under load. No strain signal, no adaptation. It does not matter how many reps you did or how much it burned.

When you apply slow, heavy load to a tendon in a stretched position, two things happen. The collagen fibers inside elongate under tension. Tenocytes, the cells responsible for maintaining tendon structure, register that strain and activate collagen synthesis. Over time, with repeated appropriate loading, the disorganized type 3 collagen gets remodeled into aligned type 1. The tendon gets stiffer, thicker along its length, and better able to handle high forces. That is adaptation.

When you apply fast load, jumping, cutting, sprinting, you also increase tendon stiffness, but through a different mechanism. Fast loading makes the tendon more rigid for better force transfer. That is the performance side. The slow, heavy, stretched loading is the health and structural side. Both matter. Most calf training programs deliver neither.

There is also a timing constraint almost nobody talks about. Tendons stop responding to loading stimulus after roughly 5 to 10 minutes of exercise. The cells activate the adaptation pathway, and then need approximately 6 hours before they can respond again. Your muscle benefits from another hour of training. Your tendon checked out after the first few sets. This has real programming implications, which we will get to.

That last number is worth sitting with. The PF leg did not get slightly less adaptation. It got none. Twelve weeks. Three sessions a week. Hundreds of reps. Tendon stiffness did not move. Not because the muscle was not working, it was. The tendon simply never received the strain signal it needed to respond.

It actually got worse. Because the muscle kept getting stronger without the tendon keeping up, the maximum tendon strain during testing kept rising through all 12 weeks in the flat ground leg. The tendon was being pulled harder and harder by a muscle that had outgrown it. That is not a missed adaptation. That is the injury mechanism building in real time.

Why Toes Elevated Calf Raises Strengthen the Achilles Tendon

The Lambrianides study did not just confirm that muscle and tendon adapt differently. It identified exactly where the difference comes from.

At 115 degrees of plantarflexion, flat ground, standard calf raise, toes pointing slightly down, the Achilles is in a shortened position. The collagen fibers are slack. Mechanical strain on the tendon is minimal. The muscle works, the tendon barely registers it. You can spend years doing flat ground calf raises and your Achilles will not meaningfully adapt.

At 85 degrees of dorsiflexion, heel dropped, toes elevated, the Achilles loaded at its longest length, the collagen fibers are under real tension. Tenocytes activate. Collagen synthesis begins. The tendon actually adapts.

And here is the clinical point that ties directly back to the injury mechanism: injuries occur in the dorsiflexed position. Not at the top of a calf raise. Not in plantarflexion. Every NBA Achilles rupture in the film review happened during a false step with the ankle dorsiflexing, knee extending, hip extending, trunk rotating forward. That is the position of maximum tendon load. That is also the position where adaptation happens. You have to train the position that breaks you.

Toes Elevated Calf Raises Also Double Your Muscle Growth

The Lambrianides study focused on tendon. But separate research on muscle hypertrophy has been running the same experiment and arriving at the same conclusion from a different angle. Training the calf at its stretched, dorsiflexed position does not just drive more tendon adaptation. It also produces significantly more muscle growth than flat ground raises.

How Long Does It Take to Strengthen the Achilles Tendon

Look. Injuries are going to happen.

You could do everything in this article and still tear your Achilles. Haliburton probably did more calf work than you and I combined. And the rupture data suggests a real "perfect storm" model, degenerative tendon structure, neuromuscular fatigue, and a specific mechanical event all converging at the same moment. No single variable controls all of that.

But that is not the point. As coaches and athletes we have an obligation to do everything the current research supports to give the body its best chance. And right now the research is clear about what that looks like. You need mechanical strain on the Achilles. You need to train at depth. You need your toes elevated on something steep enough to actually matter and a load heavy enough to actually count.

Flat ground calf raises are leaving real adaptation on the table. And in a sport where one false step can end a season, leaving adaptation on the table is not a risk worth taking.

The Angle Was Not a Random Decision

Most slant boards on the market sit between 15 and 20 degrees. That gets you into a better position than flat ground. But it does not reliably get you to the deep dorsiflexion the research identifies as the threshold where tendon adaptation actually happens. Under load, a 15 degree board compresses and the effective angle decreases. You end up training in the same middling position that flat ground produces, just slightly less flat. The tendon still does not get the strain signal it needs.

The SquatWedgie PRO was built at 25 degrees specifically to reach and hold the position the research points to. That angle gets your heel low enough and your toes elevated enough that under load the Achilles is being stretched to the length where collagen remodeling kicks in. The design intent was to consistently hit the deep dorsiflexed position that Lambrianides identified and that every study in this article found produces the most adaptation.

We did not build it that steep to be aggressive. We built it that steep because anything less is not doing the job.

Two Cues Before the Exercise

Cue one: slow down the lowering phase. Three to five seconds on the way down, every rep. The eccentric portion, the controlled descent where the Achilles is lengthening under load, is where the majority of tendon adaptation happens. Slow eccentric loading also addresses a neuromuscular issue that shows up in athletes with chronic lower leg problems: fast-twitch motor fibers misfiring during the eccentric phase, creating a visible tremor or shake. Slow eccentrics retrain that coordination pattern. Most people rush it. Slowing it down is the difference between a calf raise and a tendon strengthening exercise.

Cue two: the load has to count. To generate the internal forces that actually challenge the Achilles, roughly in line with the forces it handles during sport, you need to be loading approximately 1.5 times your bodyweight in a standing calf raise. That is the external load target to approach 80% of your maximum voluntary contraction at the tendon level. If you weigh 180 pounds, you should be working toward 270 pounds total load. Bodyweight alone is not enough. Use a Smith machine. Get the load up. Six heavy reps with a slow eccentric is worth more to your tendon than 20 light reps could ever be.

The Exercise: Smith Machine Toes Elevated Calf Raise

This is the prescription. High force, full range of motion, toes elevated, slow eccentric. This is the only combination that satisfies every condition the research identifies as necessary for Achilles tendon adaptation. Bodyweight variations have their place elsewhere. If strengthening the Achilles is the goal, this is where that work happens.

The Bottom Line

Four Achilles tears across two straight playoffs. Same position. Same mechanism. A hundred percent of NBA ruptures reviewed going back to 1992 sharing the same false step pattern. The tissue failing in the exact position it was never trained in.

The tendon needs mechanical strain to adapt. Flat ground calf raises do not produce enough of it. The dorsiflexed position is where the injury happens and where the adaptation has to happen. The research is not ambiguous about this. Multiple independent studies from 2023 to 2025 all point at the same mechanism from different directions and arrive at the same conclusion.

Toes elevated. Steep enough to matter. Heavy enough to count. Slow on the way down. Six reps. Consistent for at least 12 weeks.

Everything else is just doing calf raises and hoping.