Extreme Isometrics: Dr. Mark Wetzel on Velocity

Based on Episode 116 of the Just Fly Performance Podcast, a conversation between host Joel Smith and chiropractic neurologist Dr. Mark Wetzel.

Extreme isometrics sound like the opposite of speed training. Holding the bottom of a lunge for five minutes looks like an endurance test, and the usual objection writes itself: is that not just teaching an athlete to be slow? Dr. Mark Wetzel, a chiropractic neurologist in Memphis who works closely with the training methods associated with Jay Schroeder, argues the opposite. In his framing, an isometric hold is velocity training, because speed comes down to how fast an athlete can relax a muscle, not how hard they can squeeze one. This conversation covers what an extreme isometric actually does, why position matters more than the clock, why you should fail downward, and how Wetzel thinks about velocity and recovery.

Key Takeaways

• Position beats the stopwatch. The five-minute mark is a loose target; fatiguing repeatedly inside a hold produces more adaptation than surviving to an arbitrary time.
• Fail down, not up. As you tire you should sink deeper, lengthening the muscle at each joint angle, rather than creeping higher out of position.
• Speed is a relaxation skill. A muscle can only contract as fast as its antagonist relaxes, which is why Wetzel treats isometrics as velocity work.
• Stop the set when velocity drops. Once bar or limb speed falls a few percent off maximum, you are rehearsing a slower motor pattern.
• The squat is a test, not the goal. If the training is right, the squat should rise on its own.

What an extreme isometric actually does

Wetzel starts by dismantling the idea that a hold is a static event. In his model the muscles around the joint are cycling on and off constantly to keep you in place, which is where the velocity claim comes from.

During an isometric, you squeeze both muscles at the same time, and you’re actually creating a high velocity rate by turning the bicep and tricep on and off very, very fast. So an isometric is really velocity training. Speed is developed by one’s ability to turn muscles on and off quickly, and it’s more dependent on the antagonist muscle relaxing than on the muscle you’re trying to contract.

The second benefit is positional. Because you eventually sink under fatigue, the hold trains you across joint angles rather than at the two ends of a rep.

If you hold a lunge for five minutes and slowly fatigue down, you’re training to slightly contract one muscle and slightly relax another at each joint angle. Some people do a bicep curl and squeeze at the top and go back at the bottom, so they’re only training the top and bottom position.

That is also why he insists the failure has to go one direction. Sinking lower keeps lengthening the muscle and keeps pressure off the joint; climbing higher is the athlete escaping the position.

You want to fail in an eccentric state, because an eccentric is relaxation of a muscle. It’s lengthening. If you’re in perfect position, you’re lengthening muscle and keeping pressure off the joints, and that’s what you want. You want a longer muscle, because then you can contract harder.

Why five minutes is not the point

The five-minute lunge is the number everyone quotes. Wetzel treats it as a rhetorical device rather than a prescription.

Five minutes just came up because it sounds almost impossible, so you’re going to fatigue regardless. For someone to think five minutes is a magic number is kind of flawed, because if you can hold it for five minutes, you’re only fatiguing one time. If you can fatigue multiple times in that five minutes, you’re creating more adaptation. I don’t think the time really matters.

What does matter is the position. He argues the body adapts best in specific positions, so drifting out of the 90-degree lunge costs you the adaptation you came for.

Position is key. If you start to fatigue and your front leg bends forward or backward and you’re out of that 90 degrees, you’re not creating the most adaptation. You’re putting in more effort and getting less gain.

Speed is how fast you relax

Wetzel keeps returning to one mechanism, and it reframes what higher-rep work is for. The number of reps is not the variable he cares about; the speed of each one is.

I wouldn’t say high reps, it’s how fast you do a rep. Higher reps usually means less weight, and less weight means you can do faster movements, and faster movements is really what creates speed. It’s not about getting one muscle stronger, it’s how fast you can relax the other muscle.

It follows that the set ends the moment quality goes, and his cutoff is tight.

Once you dip below a certain level, and it’s quick, within three or four percent of your max velocity, you’re training a bad motor program. If you’re slowing down, it’s because one muscle is contracting too hard and the other isn’t relaxing enough.

His illustration is the gym-standard biceps curl performed with the elbow lowered under the biceps rather than the triceps, which he says teaches the brain an inefficient pattern.

You’re curling up with your bicep and then curling down with your bicep. The bicep isn’t actually lengthening, because the tricep is not contracting. Now you’re training your brain to move your elbow with your bicep, and that’s very inefficient.

He applies the same logic to a super-slow, 30-second squat descent driven by the hamstrings, which he uses to lengthen the quad before it has to fire.

If you contract your hamstring on the way down, it causes your quad to relax and lengthen. When the quad is lengthened, it can contract harder and faster, so at the bottom you can shoot up faster. Told to go at normal speed, most people drop and catch themselves at the bottom, so their quads are already half contracted and they lose power.

Wetzel’s energy-system model, and the claims inside it

Asked how a multi-minute hold squares with power training, Wetzel lays out a sequential model of four energy systems: an ATP phase of a few seconds, an anaerobic phase of roughly 27 seconds, an aerobic phase, and lactic acid last. It is worth flagging that this strictly linear picture is his framework rather than a consensus description, since mainstream physiology treats the systems as overlapping continuously and treats lactate as a fuel rather than a final stage. The part he builds on is the idea that each system, once entered, restores the one before it.

When you fatigue an energy cycle you go onto the next one, and that next cycle actually starts the recovery process of the previous one. So when you train the energy systems to failure, you’re increasing your ability to recover the previous energy system.

From there he pushes further than the evidence does, arguing that a high enough lactate tolerance effectively removes fatigue, and that training this way could prepare a marathon runner without running. Treat these as his claims rather than established findings.

If your threshold is super high and you have a game where you never quite reach that threshold, that lactic acid will indefinitely recover you and you will never get tired.

The same reasoning underpins the Schroeder-associated phrase that “velocity recovers,” which Wetzel explains at the muscle rather than the metabolic level, and which he is candid about not fully understanding.

I don’t think we really know why, but when we put it to the test, it clearly does. A lengthened muscle is recovered. A muscle that stays contracted is a tight muscle, and that’s essentially a fatigued muscle. The faster you can relax a muscle, the more it becomes recovered.

The squat, and what chiropractic adds

Wetzel is skeptical of chasing weight-room numbers, not because strength is useless but because a squat pursued for its own sake tends to build compensation. His reframing is the most quotable line of the conversation.

The squat should be a test to see if you’re actually training correctly. If you’re training correctly, your squat should improve.

On his own discipline, he argues that the nervous system owns most of what we call strength, and that an adjustment is useful precisely because it is fast. The 70 percent figure is his, offered without a citation.

People don’t realize that 70% of muscle strength comes from your brain telling it to work. An adjustment creates a lot of velocity, which creates a lot of feedback back to your brain. You can move the body quicker than you can move it yourself, so you’re creating more feedback, and that increases the motor units you can send back out to your muscles.

Frequently asked questions

What are extreme isometrics?
They are long-duration isometric holds, most famously a five-minute lunge held at the bottom position, associated with Jay Schroeder’s methods. Wetzel describes them as velocity training rather than endurance work, because the agonist and antagonist cycle on and off rapidly to hold the position, and because sinking under fatigue trains the muscle at every joint angle.

Do you have to hold an extreme isometric for five minutes?
No. Wetzel calls the five-minute mark a loose term that exists mainly because it sounds impossible. He argues that fatiguing several times within a hold creates more adaptation than reaching an arbitrary time once, so the clock is not the target.

Should you sink lower or hold higher as you fatigue?
Sink lower. Wetzel wants failure to happen eccentrically, so the muscle keeps lengthening and pressure stays off the joint. Drifting up out of the 90-degree position is the athlete escaping the exercise, and he says it costs the adaptation.

Do isometrics make athletes slow?
Wetzel argues the opposite. In his model, speed depends on how quickly the antagonist relaxes, and a hold trains rapid contraction and relaxation at once. He also argues that longer, lengthened muscles can contract harder.

Are the energy-system and lactate claims here settled science?
No. Wetzel’s four-system sequential model, and his argument that a high lactate threshold means an athlete “will never get tired” or could train for a marathon without running, go beyond what mainstream exercise physiology supports. They are presented here as his framework and his claims, not as established findings.

About the authors

Dr. Mark Wetzel is a chiropractic neurologist based in the Memphis, Tennessee area and the owner of New Era Chiropractic. A lifelong swimmer who competed at Indiana University, he found chiropractic after tearing a labrum in high school and now works at the intersection of sports chiropractic, neurology, and performance training, with a particular focus on the isometric and velocity methods associated with Jay Schroeder.

Joel Smith is the host of the Just Fly Performance Podcast and the founder of Just Fly Sports, a former collegiate strength and track and field coach focused on speed, power, and athletic development. Listen to the full episode with Dr. Mark Wetzel on Just Fly Sports.