The Repeated-Bout Effect

Picture from Iwannaburnfat

Those of you who are preparing for races with long downhills (like Boston) or trail races may want to know this. Or even personal trainers and strength coaches getting their athletes to do eccentric exercises.

If the long descent (or an eccentric exercise) is unaccustomed, it can cause muscle damage, soreness and a loss of strength (or delayed onset of muscle soreness - DOMs). However, repeating the same activity causes far less damage the second time. This protection is known as the repeated-bout effect. It is not commonly known how long the protection lasts. Let's see what the latest research found.

48 young males were recruited for this study. They did 2 identical exercise sessions where 5 sets maximal knee extension (straightening) exercise was peformed. Each set consisted of 15 repetitions at 60°/ sec.

4 independent groups performed the second bout of exercise 3, 6, 9 and 12 weeks after the first bout of exercise. 

Range of motion, delayed onset of muscle soreness (DOMs), muscle thickness (swelling), isometric torque (strength), echo intensity (tissue quality/ fluid accumulation), creatine kinase and high sensitivity C-reactive protein (hs-CRP) were assessed before, 2 and 4 days after each exercise bout.

Since the participants started with different levels of strength, soreness and blood markers, the researchers measured the subjects at baseline and then adjusted future data points based on their starting numbers. This allows the resarchers to evaluate how much strength each participant lost or recovered, rather than their raw strength.

The repeated bout effect was still present after 3 and 6 weeks across most outcomes and certain markers were still detectable after 9 weeks. At 12 weeks, all the protective effects were gone.

Please note that this study was done on young men performing isolated knee extension on a machine so some differences in timeline can differ in downhill running, for women and older runners.

So those of you preparing for races with long descents should ideally run a downhill-specific session every 3-4 weeks so your repeated-bout effect protection is intact. After a 3 month break or more or after the off-season, the first downhill session should be treated like a new first session. 

Picture from Iwannaburnfat

For strength coaches or personal trainers planning eccentric strength training cycles (like Nordic curls) to build injury resilience, you need to repeat the exercises within 6 weeks to maintain the protective adaptations. 

Reference

Theodorou AA, Margaritelis NV, Karyofyllidou et al (2026). The Duration Of The Repeated-Bout Effect After Eccentric Exercise. Scan J of Med & Sci Sp. e70381. DOI: 10.1111/sms.70381

How To Prevent Fading In Your Next Marathon

Exaggerated "float" phase of the run

You were running really well in your key marathon. You've trained very well, started conservatively despite feeling great hoping to have a strong negative split. You've hit all your target times at each 5 km split that you've written down on your hand.

To your greatest horror, you start to tire in the final miles of the race. Your dreams of a personal best begin to fade too.

What was the fade due to? Was it dehydration? High core temperature or low blood sugar? Apparently, none of the usual suspects according to a paper that studied 40 marathon runners immediately before a race and within three minutes of them finishing the race.

The best predictor of the runners fading was in fact muscle damage.

With each stride you run, your quadriceps and calf muscles contract "eccentrically" (lengthen instead of shorten). The muscles shorten when you push off, but they lengthen whilst you are in mid air in the double swing (or floating phase). See picture below.

This causes an accumulation of microscopic damage to your muscles. It's this eccentric contraction that causes delayed onset of muscle soreness (or DOMs).

The above mentioned study of the marathon runners showed that the eccentric contractions can literally hobble you during the race. Runners whose pace dropped more than 15 percent from the beginning to the end of the race had levels of creatine kinase and myoglobin (both are by products of muscle damage measured in blood tests) 53 and 112 percent higher than the runners who managed to maintain a steadier pace.

When I read the paper, my first thoughts was that the runners who faded did not train enough as those who didn't. However, the researchers suggested that age, running experience and training were not significant enough to explain the differences.

The authors suggested three ways to prevent fading in your next marathon.

Doing your long run close to your target marathon pace is crucial to get your muscles stronger. A 30 km run at or close to your target race pace three to four weeks before to simulate the effort will lessen the chance of muscle damage in the race.

Due to the "repeated bout effect", it will be harder to trigger as much muscle damage once they have recovered. You will need to run harder or faster to trigger similar damage.

The second way to increase your ability to withstand eccentric muscle damage is with weight (or resistance) training. Eccentric lunges and squats of at least 80 percent of the heaviest weight you can lift will help prevent damage to your muscles. Do the weight training twice a week during your training cycle and cut back to once a week when you are tapering for the race.

Be sure to practice downhill running if your race has downhill sections. Running downhill causes lots of eccentric contractions, a sure fire way of triggering muscle damage. Experiment with your stride to find the best way of descending as lightly as possible to minimize the muscle damage.


Reference

Del Coso J, Fernandez De Velasco D et al (2013). Running Pace Decrease During A Marathon Is Positively Related To Blood Markers Of Muscle Damage. PLoS One. 8(2): e57602. DOI: 10/1371/journal.pone.0057602.

Rhabdomyolysis - The Scary Side Effects Of Exercise

My patient just attended her first spin class with her colleagues. Prior to this, she's been running and wakeboarding for exercise.

The doors to the studio were shut, while the air conditioning was turned off. Other than that, she didn't find pedaling fast on the stationary bike to rhythms of popular music while an instructor shouted motivation too difficult. Neither did she feel she pushed herself too hard. Her legs at the end of the hour long class weren't too sore or wobbly afterwards.

Over the next two days, her legs started throbbing and she came into the clinic to see me. I noticed bruises on her thighs and asked if she knocked them against the stationary bike. She said she didn't recall that happening.

The next day she noticed blood in her urine and checked herself into a hospital where she was warded and after blood and urine tests and was told her she had rhabdomyolysis.

Rhabdomyolysis is rare but can be a life threatening condition often caused by extreme exercise. It occurs when muscles that have been overworked dies and leak their contents into the bloodstream. This strains the kidneys and can cause severe pain.

My patient ended up staying in hospital for a few days before being discharged and has since recovered.

Subsequently I saw an article that documented three unusual cases of rhabdomyolysis, each occurring after a first spin class all treated by the same doctors (Brogan et al, 2017).

The article also described 46 other cases of people developing rhabdomyolysis after a spin class (42 of them in people taking their first spin class). The authors wrote that the condition was rare and not a reason to avoid high intensity exercise.

Another published study found 29 cases admitted to the emergency department between 2010-2014 for exercise induced rhabdomyolysis. Weight lifting, running, cross fit were some of the causes, but the most common cause was spinning classes!

The patients were not unfit, they were in fact being pushed too hard. Since they were not used to the new exercise, they ended up getting really bad muscle trauma.

Remember this next time you try a new exercise. Rhabdomyolysis occurs when you do not give your muscles time to adjust to a new aggressive exercise. When you stress your muscles too much, they tend to break down, releasing contents like myoglobin into your bloodstream which causes brown or tea colored urine, a classic symptom of rhabdomyolysis.

While any intense activity can cause rhabdomyolysis, it almost always strikes the person doing something new. So when you try a new exercise, start moderately first.

Know your limits, don't be pressured by the instructor. You can stop the exercise if you're struggling. Exercise can be dangerous when your body is not prepared for really intense levels.


References

Brogan M, Ledesma R et al (2017). Freebie Rhabdomyolysis: A Public Health Concern, Spin Class-Induced Rhabdomyolysis. AJM. 130(4): 484-487. DOI: 10.106/j.amjmed.2016.11.004.

Cutler TS, DeFilippis EM et al  (2016). Increasing Incidence And Unique Clinical Characteristics Of Spinning-induced Rhabdomyolysis. Clin J Sp Med. 26(5): 429-431. DOI: 10.1097/JSM.0000000000000281.

Here's a picture of a spin class.

Picture from Soulcycle.com

Can Antihistamines Decrease Muscle Soreness?

I still shave/ wax my legs. Not as often as before, but I still try to keep them hair free.

Ever since my racing days, I've been making sure my legs are free of hair. Why is that so you should be asking?

In the event of a bike crash and the resulting abrasions, the wounds are easier to clean if there is no hair on the skin.  From time to time I need to take Clarityn (which is a relatively mild antihistamine) for my hives that result from the ingrown hair.

Easier to clean the wounds with no hair

I sometimes use Clarityn for mild allergies as well. Piriton (or chlorphenamine) is stronger, but it makes me very drowsy.

So I was surprised to read that taking a single dose of antihistamines can help lessen delayed onset of muscle soreness (or DOMs) after a hard workout.

After a hard workout, blood flow to your muscles remain elevated for a while. Histamines (part of your body's immune response) play a role in triggering this post exercise blood flow, which may be linked to inflammation and subsequent repair of muscle.

The researchers' aim was to investigate if blocking histamines with antihistamine medication would reduce post exercise blood flow, reduce inflammation and increase muscle damage and DOMs.

The subjects had to run downhill on a 10 percent grade for 45 minutes after taking the antihistamine medication (control group didn't take). Blood flow, inflammatory markers, pain sensitivity, perceived soreness and strength were measured for three days.

Results showed that blood flow to the legs was reduced by 29 percent an hour after exercise in the antihistamine group. There were however no differences in markers of inflammation.

Creatine kinase (used to determine muscle damage) levels were very different. This seems to supports the idea that blocking histamine receptors resulted in increased muscle damage.

The control group (didn't take medication) was 19.3 percent weaker the day after the hard workout compared to the group that took the antihistamines (7.8 percent weaker).

Before you rush to the nearest pharmacy to buy some Clarityn, do bear in mind that the results were a little more complex after you examine them closely.

This is very similar to what I wrote a few weeks earlier about the balance between recovery and adaptation.

The researchers themselves do not know exactly why this is so. It is possible that the antihistamine medication make you feel less pain and soreness (even if there was more damage in your muscles).

This makes antihistamines a double edged sword. They may make you more prone to muscle soreness even though you may not feel it.

If, however you want an edge to reduce next day soreness and strength loss when you have back to back races or games then taking antihistamines may help.

If you interfere with the recovery process to make yourself better soon (or recover faster), do you then risk delaying the repair or adaptation process? It is a short term versus long term trade off.

Reference

Ely MR, Romero SA et al (2016). A Single Dose Of Histamine-receptor Antagonists Prior To Downhill Alters Markers Of Muscle Damage Andd Delayed Onset Muscle Soreness. J Appl Physiol.
DOI: 10.1152/japplphysiol.00518.2016.