Does your mouth taste like cardboard or sawdust after doing intense cardio, particularly of an agitated nature such as jumping?
This is likely caused by exercise-induced acid reflux.
In fact, for healthy people to whom this happens, it’s not uncommon for them to experience no odd taste in their mouth from smoother or less erratic forms of cardio or hard exercise such as briskly walking up steep hills, fast pedaling or leg pressing against resistance.
A paper in the Journal of the American Medical Association (Clark et al) describes how acid reflux as a result of exercise is more likely to occur when the activity is of an agitated nature.
For instance, running or jumping gets things in the digestive tract more shaken up than does being seated on a bike and pedaling or seated in equipment and pushing a stack of weights.
For the Clark et al study, 12 healthy people exercised for one hour. Activity included stationary pedaling, running and strength training.
Each type of exercise was done for 15 minutes with a five minute break in between.
The result of the study showed that vigorous exercise can cause gastroesophageal reflux in healthy subjects.
Of the exercises done in this study, running led to the most reflux, and pedaling induced the least. Running had the most agitated effect on the body, while pedaling had the least.
I was inspired to write this article after realizing that at the conclusion of my five minute Tabata-style jumping regimen, I’d have a cardboard or sawdust taste in my mouth.
No other exercise that I do causes this. Not the heavy deadlifts, fierce leg press routine, stool stepping, incline dashing or lengthy hikes.
The one thing that separates the jumping routine from other exercise is its agitated nature – in terms of shaking things up inside the gut.
Just five minutes’ of rapid jumping sets (e.g., shallow but quick switch jumps, forward bunny hops, backward and lateral bunny hops) with only 15 seconds’ rest in between each set, are all it takes to induce an unpleasant taste – which can best be described as cardboard or sawdust.
I might add that this is a new-onset phenomenon, something that wasn’t always there. So why is it new?
My theory is that over time, I have added hand weights to this jumping regimen (as my body has adapted), which is based on the Tabata concept.
I start out with a 20 pound dumbbell in each hand and end with five pounds in each hand (straight arms).
The cardboard taste after this intense and frenetic cardio lingers for only a few minutes and then it’s gone.
Is there a way to confirm it’s acid reflux?
“On the assumption that it’s acid reflux you could do a therapeutic trial,” says Dr. David Beatty, MD, a retired general practitioner with 30+ years of experience and an instructor of general medicine for 20 years.
“Take an antacid, like Gaviscon, just before exercise and see if that stops the cardboard taste.
“Alternatively, try one of the stronger acid suppressing tablets, like ranitidine [Zantac] or lansoprazole [Prevacid], an hour or two before exercise. If either of these help, you have your diagnosis.”
Dr. Beatty has worked in primary medicine, surgery, accident and emergency, OBGYN, pediatrics and chronic disease management. He is the Doctor of Medicine for 
