By June, somewhere past the two-hour mark on a long Folsom Lake loop, my right forearm would start to burn from the shaft, and a dull ache would settle into my elbow and the back of my shoulder. Nothing was sharp and nothing stopped me, and I never tore anything: no pop, no swelling, no trip to urgent care.
Early spring paddles had felt fine. The elbow and shoulder ache was the loudest signal, and it showed up late, when my form was falling apart from fatigue. I went into the tendinopathy research to figure out what builds a tendon’s tolerance for load, and that road led to isometric holds.
Key Takeaways
- Isometrics are holds, not stretches. An isometric contraction means the muscle works hard while the joint stays still. Pressing your palm into a doorframe without moving is isometric. A calf stretch is not.
- Holds build a tendon’s tolerance for load and can quiet pain for a while afterward. They are a well-tolerated entry point, and pooled trials have not found them superior to ordinary moving-load exercise.
- Four regions do the suffering in paddling: forearm and wrist, elbow, shoulder (rotator cuff and biceps), and the Achilles and lower leg from standing balance.
- A workable rule of thumb is a firm hold of roughly 30 to 45 seconds, several reps, at an effort that stays around 3 to 4 out of 10 for pain and settles within a day.
- Form is the upstream fix. A stacked, torso-driven stroke and a relaxed grip prevent far more tendon trouble than any exercise reverses.
- Isometrics are one stage of progressive loading. The through-line runs isometric to isotonic or heavy slow resistance to energy-storage work as tolerance grows.
- No study has tested isometric loading in SUP paddlers specifically. Every protocol number here is borrowed from patellar, Achilles, elbow, and shoulder research and applied by analogy.
- See a professional for sudden loss of strength, numbness or radiating pain, night pain, visible swelling or a gap in the tendon, or pain that keeps climbing over weeks.
Medical disclaimer: This is educational writing based on published sports medicine research, not medical advice. The routines here are preventive, aimed at healthy paddlers managing early warning signs. If you have real pain, weakness, or an existing injury, get assessed by a physical therapist or physician before loading anything.
What Isometric Holds Do for Your Tendons
The common phrase “isometric stretches” is a contradiction. A stretch lengthens tissue. An isometric contraction does the opposite: the muscle fires while the joint angle holds dead still. You produce force and go nowhere.
Push against a wall that will not move and you are doing an isometric. A tendon under a steady, controlled load adapts in a way that a passive stretch never asks it to.
The tendon continuum framework describes a slide from a reactive, irritable state through failed healing into degeneration, with load management as the lever that pushes tissue back toward health or further toward breakdown (Cook and Purdam, British Journal of Sports Medicine, 2009).
Too little load and the tendon deconditions. Too much, too fast, and it flares. The job is a dose that challenges the tissue without tipping it over.
Isometrics earned their reputation from a small, much-cited study of jumper’s knee. Heavy holds produced an immediate drop in pain that lasted well past the session, alongside a measurable jump in strength and reduced inhibition of the muscle, while a matched moving exercise did not (Rio et al., British Journal of Sports Medicine, 2015).
When researchers pooled the comparison trials, isometric loading was not superior to ordinary moving-load exercise for tendon pain, and the response varied a lot from person to person (Clifford et al., meta-analysis of 10 randomized trials and 294 patients, BMJ Open Sport & Exercise Medicine, 2020; see also van Ark et al., Journal of Science and Medicine in Sport, 2016). Some sessions land, others feel nothing special.
For a paddler catching early warning signs, isometrics are the low-risk way in. They are easy on an irritable tendon, they need almost no equipment, and they build the load tolerance you will need before you progress to heavier work.
Why Paddling Puts Tendons at Risk
Stand-up paddling produced 3.63 injuries per 1,000 hours on the water in the first injury survey of the sport, with the shoulder and upper arm the most affected region at 32.9 percent (Furness et al., Orthopaedic Journal of Sports Medicine, 2017). Muscle and tendon problems made up 50.4 percent of injuries. The elbow and forearm took another 11.8 percent. Endurance paddling was the top mechanism, blamed for 34.5 percent of the total.
A biomechanical analysis broke each stroke into an entry or catch, a drive, and an exit, and found that less experienced paddlers reach into more extreme shoulder positions and keep the elbow more bent than skilled paddlers do (Schram et al., PeerJ, 2019).
Every catch loads the front of the shoulder and the tendons crossing the elbow. Multiply by a cadence of roughly 30 strokes a minute across two hours and you get the volume that turns a healthy tendon irritable.
The Four Tendon Trouble Spots (and the Isometric Hold for Each)
Forearm and Wrist
The forearm burn came first for me. The extensor tendons on the back of the forearm co-contract to stabilize your wrist while the flexors squeeze the shaft, and a sustained grip above roughly 15 percent of maximum effort begins to choke off blood flow to the working muscle, which is why the burn climbs as the miles add up.
Overgripping is the root cause, and it feeds every problem further up the arm.
The hold: an isometric wrist-extension press. Rest your forearm on your thigh, palm down, and let the other hand push gently against the back of your hand while you resist, keeping the wrist still. Hold a firm but comfortable effort for 30 to 45 seconds, two or three times. A relaxed-grip squeeze on a soft ball works the flexor side.
These numbers come from tendon protocols in other body parts, so treat them as a starting dose adjusted by feel.
The form fix: hold the shaft at a 3 to 4 out of 10 grip, no white knuckles. I wrote a separate piece on why the death grip wrecks your hands.
Elbow (Paddler’s Elbow)
My elbow ache came in second. On the outside of the joint, the common extensor tendons take the strain, the same tissue that gives tennis players lateral epicondylitis. On the inside, the flexor-pronator tendons do the golfer’s-elbow version.
Both come from gripping hard while the forearm rotates through the stroke, which is what a bent-elbow, arm-pulling technique produces.
Isometric exercises for elbow tendonitis usually center on the same wrist-extension hold, dosed progressively. One protocol for lateral elbow pain built from a lighter hold at around 20 percent of maximum effort toward roughly 35 percent as tolerance improved (Vuvan et al., Medicine & Science in Sports & Exercise, 2020).
In that research, isometric loading on its own looked doubtful as a sole treatment for the elbow. The tendon still needs progressive strengthening to get more robust. Use the holds to calm an irritable elbow and keep training, then layer heavier moving loads on top as symptoms allow.
The form fix: drive the paddle with your torso and a longer, straighter lever arm instead of yanking with a cranked elbow. Less bend, less grip, less rotational strain on the tendon origins.
In September 2026 my right elbow gave out in the finishing sprint of a technical race at USA SUP Nationals, and I wrote up that injury and the peer-reviewed research on it. The race medical team taped it with kinesiology tape.
Shoulder (Rotator Cuff and Biceps)
At the catch, the rotator cuff (the supraspinatus in particular) and the long head of the biceps control an arm reaching forward and overhead. Reach too far, too often, with a fatigued cuff, and those tendons get cranky.
Isometric exercises for shoulder tendonitis run anywhere. Stand in a doorway, elbow bent 90 degrees at your side, and press the back of your wrist outward into the frame as if starting an external rotation, without letting the arm move. Hold 10 to 20 seconds, three to five times through the day. A scapular hold, squeezing the shoulder blades gently down and back, trains the platform the cuff works from.
The evidence for cuff isometrics is thinner than the lower-limb research, so lean on these to manage symptoms rather than expecting them to rebuild the shoulder alone. A light resistance band lets you dial the effort precisely once you graduate to moving work.
The form fix: stop over-reaching at the catch. Plant the blade where a stacked, upright stroke can catch it, keep the shoulders level, and let the torso do the pulling.
Achilles and Lower Leg
No study has looked at Achilles loading in paddlers, so the reasoning here is inference. You stand on a moving platform for hours, and the calf and posterior tibial tendons make thousands of tiny balance corrections to keep you upright. That is low-grade, sustained work, the kind tendons grumble about over a long season.
The hold: a calf-raise hold, rising onto the balls of your feet and holding still for 30 to 45 seconds, gently loads the Achilles. A Spanish squat, sitting back against a strap looped around a fixed post and holding, targets the knee tendons that fatigue from staying braced on the board. Both borrow their dosing from lower-limb research.
The form fix: paddle with soft, unlocked knees and let your ankles absorb the chop with active balance rather than a rigid stance. A stiff lower body transfers every wobble straight into the tendons.
Proper Paddling Form Is the Real Prevention
Stack the stroke vertically. A paddle planted close to the rail and pulled in a straight line loads the shoulder and elbow far less than a sweeping, angled pull.
Rotate from the torso instead of arm-pulling, so the trunk generates the power and the arm mostly transmits it. Keep the top-hand grip loose. Set the catch without lunging for reach you cannot control, then let the blade lock in before you load it.
A bent-elbow, over-reaching pattern stacks load onto the tendons that flare (Schram et al., PeerJ, 2019). Fix the pattern and you cut the dose at the source. Technique work pairs well with a full off-water strength routine for core, balance, and shoulder resilience.
A Simple Weekly Isometric Routine
This preventive week is for a healthy paddler managing early warning signs, built around short holds you can do at home. I borrowed the numbers from tendon research in other joints, so adjust them to your own response rather than treating them as a prescription.
| Exercise | Hold | Sets | Days per week |
|---|---|---|---|
| Isometric wrist-extension press (forearm and elbow) | 30 to 45 sec | 3 | 4 |
| Relaxed-grip ball squeeze (forearm flexors) | 20 to 30 sec | 3 | 4 |
| Doorframe external-rotation hold (shoulder cuff) | 10 to 20 sec | 3 to 5 | Most days |
| Scapular squeeze-and-hold (shoulder platform) | 10 to 20 sec | 3 to 5 | Most days |
| Calf-raise hold (Achilles) | 30 to 45 sec | 3 | 3 |
| Spanish-squat hold (knee and lower leg) | 30 to 45 sec | 3 | 3 |
Pain during a hold should stay low, around 3 to 4 out of 10, and settle back to baseline within about a day, with no worsening from one session to the next.
That is the mainstream clinical convention. The classic Achilles protocol from Alfredson deliberately loaded patients into pain, so reputable programs disagree on how much discomfort is acceptable.
When you are unsure, back off and get a professional eye on it rather than guessing.
Isometric Versus Eccentric Versus Heavy Slow Resistance Versus Stretching
| Approach | What it is | Best role | Evidence snapshot |
|---|---|---|---|
| Isometric holds | Static contraction, joint still | Entry point; calm an irritable tendon; build baseline tolerance | Helps some with symptoms; not proven superior to moving loads (Clifford, 2020) |
| Eccentric loading | Slow lowering under load | Rebuilding a tendon’s capacity once it tolerates load | Strong track record; Alfredson’s Achilles protocol returned all 15 subjects to running (Alfredson et al., 1998) |
| Heavy slow resistance | Controlled lifts, slow tempo, both directions | The modern workhorse for strengthening | Matched eccentric results with higher patient satisfaction, held at one year (Beyer et al., 2015) |
| Static stretching | Passive lengthening | Mobility, not tendon repair | Limited evidence for tendinopathy; can aggravate tissue at compressive sites |
Start with isometric holds when a tendon is irritable and you want a low-risk way to keep loading it. As it settles, graduate to eccentric work or heavy slow resistance, where the strengthening happens.
Heavy slow resistance has become the default in many clinics because it matched the older eccentric results while patients found it easier to stick with (Beyer et al., American Journal of Sports Medicine, 2015). Stretching has its place for mobility on rest days, but it is not a tendon-repair tool, and around compressive spots it can make things worse.
When It’s More Than a Warning Sign
Get assessed by a physical therapist or physician if any of these show up:
- A sudden pop with loss of strength or function. That can signal a tendon rupture and it is not a wait-and-see situation.
- A recent course of fluoroquinolone antibiotics. Ciprofloxacin, levofloxacin, and moxifloxacin carry an FDA boxed warning for tendinitis and tendon rupture, most often the Achilles. The risk stays elevated for months after the last dose, and it is higher again if you are over 60, taking corticosteroids, or have had a kidney transplant. If that is you, talk to your doctor before starting loaded calf holds.
- A corticosteroid injection near the tendon in the last few months. Same reasoning. Get clearance on timing and loading before you add holds.
- Weakness that has crept up over weeks with no pop. Degenerative rotator cuff tears often arrive this way, quietly, and the shoulder is the most-injured region in this sport. Gradual loss of strength deserves the same appointment a sudden one does.
- Fever, spreading redness, or a joint that is hot to the touch. That is a same-day medical problem.
- Numbness, tingling, or pain that radiates down the limb. That points to nerve involvement rather than tendon overload, and it calls for a different approach. My separate guide to nerve glides for paddlers covers that territory.
- Pain at night or at complete rest. Tendon pain that wakes you or lingers when the limb is still has usually progressed past simple overuse.
- Swelling, warmth, or a palpable gap in the tendon. Visible or feelable changes in the tissue need imaging, not exercise.
- Pain that keeps climbing over weeks despite backing off the load. If sensible load management is not helping, the diagnosis may be wrong.
- Pain above 4 to 5 out of 10 that does not settle within 24 hours. That is the tissue telling you the dose was too high.
I am a paddler who reads the research, not a clinician, and I built these routines for prevention. If you are past the warning-sign stage, a hands-on assessment beats anything an article can offer.
The Bottom Line
Isometric holds are a low-risk first stage for a paddler who feels the early warning signs. Pooled trials have not found them better than moving loads, and no study has tested them in paddlers, so hold them lightly as one stage of a bigger plan that runs toward eccentric and heavy slow resistance work. Clean up your stroke, loosen your grip, and stop over-reaching at the catch, and the exercises have far less to undo.
Frequently Asked Questions
Are isometric exercises good for tendons?
They can be a useful, low-risk starting point. Isometric holds load a tendon without joint movement, which is often well tolerated when the tissue is irritable, and they reduce pain for a stretch of time afterward. Pooled trials found isometrics were not superior to ordinary moving-load exercise, and the response varies person to person (Clifford et al., 2020). Treat them as one stage of a progressive loading plan, not a stand-alone fix.
Do isometric exercises strengthen tendons?
They build tolerance and can produce short-term strength and pain changes, but they are not the main strengthening tool. The heavier work comes from eccentric loading and heavy slow resistance, which have the stronger track record for rebuilding tendon capacity (Beyer et al., 2015). Isometrics are best understood as the on-ramp that gets an irritable tendon ready for that work.
How long should you hold an isometric contraction?
A common range borrowed from tendon research is roughly 30 to 45 seconds per hold for larger regions like the calf, and shorter holds of 10 to 20 seconds for the shoulder cuff, repeated for several reps. Those numbers come from studies in the knee, Achilles, and shoulder, not from any paddling trial, so use them as a starting point and adjust to your own tolerance.
Is it normal for an isometric hold to hurt?
A low level of discomfort, around 3 to 4 out of 10, that settles within about a day is the mainstream convention for tendon loading. Sharp pain, or pain above 4 to 5 out of 10 that lingers past 24 hours or worsens session to session, means back off. The classic Alfredson Achilles protocol deliberately loaded patients into pain, so experts do not fully agree on the pain threshold. When unsure, err toward less.
Eccentric vs isometric for tendonitis: which is better?
They do different jobs. Isometrics are the gentle entry point for calming an irritable tendon and holding baseline load. Eccentric exercise, the slow-lowering work, has a long record of rebuilding tendon capacity (Alfredson’s Achilles protocol returned all subjects to running). Heavy slow resistance matches eccentric results with better adherence (Beyer et al., 2015). Sequence them: isometric first, then eccentric or heavy slow resistance as tolerance grows.
How often per week should I do isometric holds?
For prevention, most protocols run something in the range of daily for the small shoulder holds down to three or four days a week for the larger regions. In-season tendon studies have used around four sessions a week for four weeks. Spread the work so no region gets loaded hard two days running, and let paddling days count toward your total load.
Can you keep paddling with tendonitis?
Often yes, if the pain is low and settling, because complete rest tends to decondition a tendon rather than heal it. The goal is load management: reduce distance, clean up your stroke, and keep the tissue loaded within a tolerable range. If pain is high, radiating, waking you at night, or paired with weakness, stop and get assessed before continuing.
Are isometrics stretches?
No. A stretch lengthens the muscle and tendon. An isometric contraction holds the joint still while the muscle produces force, so the tissue is loaded, not lengthened. The common phrase “isometric stretches” mixes up two opposite things. If you are holding a position and working hard without moving, that is an isometric.
When should I see a doctor for paddling tendon pain?
See a professional for a sudden pop with loss of strength, numbness or radiating pain, night or rest pain, visible swelling or a palpable gap in the tendon, pain that keeps worsening over weeks despite backing off, or pain above 4 to 5 out of 10 that does not settle within a day. Those signs point beyond simple overuse, and early assessment usually means a shorter time off the water.
Do you need equipment for isometric tendon work?
Almost none. A doorframe handles the shoulder external-rotation hold, a wall or your own opposite hand handles the wrist press, and your body weight covers the calf and Spanish-squat holds. A soft ball helps the grip work and a light resistance band is handy once you progress to moving loads, but you can run the whole preventive routine with what is already in your house.
A few things I use for the moving-load stages, once you progress past bodyweight:
- A flexible therapy bar for progressive elbow and wrist tendon loading once you move past isometric holds.
- Hand therapy putty for the relaxed-grip forearm squeeze.
- A high-density foam roller for calf and forearm recovery between sessions.
Affiliate Disclosure: Some links in this article are affiliate links. If you buy through them, I may earn a small commission at no extra cost to you. I only recommend gear I would use myself, and the routines here work fine with equipment you already own.
Article Updates
- October 10, 2026: Replaced the lead photo with one from the men’s inflatable sprint final at the 2026 USA SUP National Championships and rewrote the introduction. Edited for clarity.
- September 23, 2026: Linked the write-up of my acute elbow injury at USA SUP Nationals from the elbow section.
- August 4, 2026: Added missing red flags. Fluoroquinolone antibiotics carry an FDA boxed warning for tendon rupture, and the risk stays elevated for months after the course ends, which matters in an article that prescribes loaded calf holds. Also added recent corticosteroid injection near a tendon, weakness that builds gradually without a pop, and signs of infection.
- July 13, 2026: Article published.
