Sunday, August 2, 2015

What Causes Muscle Cramps?

Picture by Jon Candy from Flickr
A patient came in to see me yesterday and complained  that if not for a muscle cramp near the end of her recent race, she would have won her age group and also gotten a personal best timing.

After putting it up on Facebook, she had many, many unsolicited comments : Eat bananas, take salt tablets, drink Gatorade, have some pretzels. Knowing that I used to race, she wanted to know my thoughts and get some advice on what else but how not to cramp during a race.

While her friends and even strangers who posted on her Facebook page meant well, none of their advice will help her as even expert exercise physiologists can't say for sure what causes exercise induced cramps.

The most common and popular theory on cramps is that they are caused by sodium (or salt) loss and dehydration. Fluid and electrolyte loss. This has been the focus of much Gatorade (or other companies) sponsored research. More on that in another post definitely.

Tim Noakes, possibly the most renown sports scientist on this topic found no significant differences in sodium and magnesium levels of 72 ultra marathoners between those who cramped and those who didn't cramp. There was no differences in body weight, plasma (or blood) volume between the two groups, showing that dehydration had no real effect on cramps.

Dehydration could however hasten muscle fatigue. And this is what Noakes and most exercise scientists believe is the likely cause of cramps.

In the above ultra marathoner study, 100 percent of the runners cramped in the last half of the race or right after the race. Think about it, when was the last time you had a muscle cramp? At mile 20 (or 32 km) in a marathon or after 3 km in a 5 km race?

This explains why cramping is most likely to occur during races than training. You tend to start off too fast or you pushed yourself too hard. Other studies have found that tough, hilly course and poor pacing (starting too fast) are predictive of muscle cramps.

So, anything you can do to prevent muscle fatigue should then help to prevent cramps. The obvious though undesirable strategy is to simply slow down. Not what you would want to hear or read!

Since guarding against muscle fatigue is key, you can't take any short cuts in training. Train more, do longer distances. You simply have to adapt to the distance you want to race. There is no substitute for strength work that is running specific. Gotta love hills and speed work.

Plyometrics (or explosive exercises) may improve the endurance of the receptors in your muscles that are thought to cause muscle cramps.

Knowing your own capabilities is key as you can choose a pace right from the onset of the race. Cramps are more likely to happen to athletes who start too fast.

"That's it"? My patient said. Yes, that's it.


Schwellnus MP, Nichol J, Laubscher R and Noakes T. (2004). Serum Electrolyte Concentrations And Hydration Status Are Not Associated With Exercise Associated Muscle Cramping (EAMC) In Distance Runners. BJSM. 38: 488-492. DOI: 10.1136/bjsm.2003.007021.

Sunday, July 26, 2015

Ice Vest Improve Your Race Performance?

Cooling vests by Cozy winters
You may have seen elite athletes (like Alberto Contador above) donning an ice vest prior to their events and wondered if that really helps. Well they do, but a recent study showed that precooling your legs may be much more effective (than an ice vest) before a race in hot, humid conditions.

The researchers had their runners complete three randomized 5 km time trials on a treadmill in a laboratory at about 90 degrees Fahrenheit (about 32.2 degrees Celsius) and close to 50 percent humidity.

The runners did a 30 minute warmup consisting of jogging, static and dynamic stretches, more jogging and some short strides to finish.

One group of runners did warmup with an ice vest and another with ice packs covering the thighs (the researchers developed shorts with pockets on the front and back of each high to hold frozen gel packs). The third group was a control group with no cooling devices.

The runners' core and skin temperature, heart rates, perceived rates of exertions were measured during the time trials. Runners with ice packs on their thighs ran the 5 km 85 seconds faster than the control group. Those with the ice vests ran 45 seconds quicker than the control group.

The 5 km times in the study were a lot slower than the runners' own personal bests (19:30 on average compared to 23:45 min after the thigh pre cooling). The authors suggested that this was due to the hot conditions, the fact that the runners could control their pace on the treadmill and that they were not in a race environment.

The authors suggested improvements even in cooler conditions, down to 70 degrees Fahrenheit (or 21.1 Celsius).

The authors cautioned that not everyone will shave 85 seconds off their 5 km race times if you employ such a strategy before your next race in the heat, but there will be some level of benefit.

This study is unique as the runners performed an active, sport specific warmup before the race to mimic what runners actually do before a race.

The authors suggest using an elastic bandage over frozen gel packs on your thighs as an alternative to ice shorts or vests.

Oh, and remember to drink a slushie too.


Randall CA, Ross EZ et al (2015). Effect Of Practical Precooling On Neuromuscular Function And 5-km Time-trial Performance In Hot, Humid Conditions Amonh Well-trained Male Runners. J Strength Cond Research. 29(7): 1925-1936. DOI: 10.1519/JSC.0000000000000840.

From Amazon

Sunday, July 19, 2015

Protein Before Bed Builds Muscle

Night time snack before zzzzz
You can't simply build muscle eating lots of protein. To build muscle you need a combination of resistance training and protein. Recent studies show that the most effective way to trigger muscle growth is to spread your protein intake in several doses of 20-25 grams throughout the day.

A group of researchers have previously demonstrated that if you consume protein right before sleeping it can increase the rate protein synthesis (the process of making protein) by 22 percent during overnight recovery from exercise.

This same group of researchers now wanted to know if consuming protein before bed would increase the muscle adaptive response to weight training.

They did a 12 week double blinded study on a bunch of volunteers who weight trained three times a week. The subjects drank either a protein drink or placebo before bed. The protein drink contained 27.5 grams of protein and 15 grams of carbs.

The results showed that the group that had the protein drink had significantly greater improvements in muscle strength, muscle size and even muscle fiber size (done by muscle biopsy).

The subjects were already consuming diets that were fairly high in protein (1.3 grams/kg) and they also had a protein snack (10 grams of protein) after each workout.

How should you snack up on your pre bedtime meal? A cup of low fat milk has about eight grams of protein, and if you had some toast and peanut butter that will probably do the trick.

Don't forget to weight train too.


Snijders T, Res PT et al (2015). Proten Ingestion Before Sleep Increases Muscle Mass And Strength Gains During Prolonged Exercise Training In Healthy Young Men. J Nutri. 145(6): 1178-1184. DOI: 10.3945/jn.114.208371.

Sunday, July 12, 2015

How Much Water To Drink After Exercise?

Picture by Daniel Orth from Flickr
I was reading a paper on the 24-hour hydration status in runners after a dehydrating run and testing what measurements are reliable to detect this when I thought of a very funny thing that happened at the Olympics.

As Team Singapore's Physiotherapist at the Beijing 2008 Olympics, other than treating the athletes, I was sometimes roped in to help test our Singaporean athletes' hydration status (since we only had one nutritionist and no exercise physiologist at the games).

Director of High Performance and other senior management at Singapore Sports Council (now SSI) decided that in order to perform well and/ or win medals, our athletes needed to be amply hydrated at all times.

Some of our athletes complained about this rather strongly as they were asked to drink more water when their hydration status showed that they need more fluids. These athletes complained that after consuming more water they had to get up in the middle of the night to pee and afterwards could not fall asleep again for a long time.

You know what they did? They simply added water to their urine samples to pass the hydration test. Our staff got their testing done, the athletes got their much deserved sleep. No names will be mentioned to protect the athletes involved.

Anyway, back to the study.

The group of runners in the study ran in hot conditions until they lost about three percent of their starting weight on three occasions. The three rehydration protocol was either 3.2, 4.2 or 5.2 litres of fluid over the next 24 hours.

Rehydration in the first 24 hours were assessed by measuring body weight of the runners, urine colour, urine specific gravity (a measure of urine concentration) and reported thirst sensation.

The most sensitive marker for fluid consumption during the first 12 hours was urine specific gravity. (Atago - which measures devices to measure specific urine specificity was used and they also sponsored this study).

Thirst emerged as a very sensitive and reliable marker by the end of the 24 hour period. The problem is that differences in thirst did not appear after the run but only emerged the next morning so you may go to bed not knowing you've not drunk enough water.

When the runners drank a lot, they urinated more, when the drank less, they urinated less. You may be surprised with this but when food and fluid intake were tightly controlled, the runners' body weight was unable to detect low fluid intake. The researchers concluded that body weight wasn't a particularly helpful way of tracking how much you're drinking.

There were only subtle changes in urine colour when measured on the researchers 8-point scale. So you have to pay close attention to the shade of your urine colour should you choose to to use this cue.

4.2 litres corresponded to replacing about 100 percent of the sweat losses within the first 12 hours of their run and 200 percent within 24 hours. This was sufficient to return the runners to normal by the time they were ready to run again the next day.

Turns out it corresponded most closely to how much the runners would have normally drunk too.


O'Neal EK, Stevenson MC et al (2015). Hydration Assessment Technique Over 24-h Post-run With Low, Moderate, And High Fluid Replacement. ACSM Annual Meeting. May 28, 2015. Abstract here.

With the then Singapore President at the 2008 Olympics

Sunday, July 5, 2015

Blood Poisoning In Extreme Endurance Events

Picture by orangefan_2011 from Flickr
If you haven't trained hard enough for your upcoming marathon or ultra marathon race, beware for there may be more adverse effects than you think.

Extended exercises beyond four hours can put your body at risk if you are not sufficiently prepared. Stomach bacteria may seep into your bloodstream and cause poisoning.

Two different studies looked at runners taking part in two different ultra distance races in Scotland (between 78-130 miles) and Spain (5-day 143 miles stage race).

Before and after the races, blood samples were taken from the runners and a control group not racing.

Blood markers in most of the runners after the races showed traces of blood poisoning. This was similar to what you see if you were admitted to the hospital for food poisoning. Almost all the runners had stomach issues during the race as well. None were hospitalized though.

Some runners even had blood markers resembling those who have sepsis - a potentially life threatening illness where chemicals released into the bloodstream to fight infection actually generate heavy inflammation.

This happens when blood moves away from the stomach area to the working muscles when we exercise. This causes the stomach wall to spread apart and leave open gaps. Endotoxins (naturally occurring bacteria in the stomach) fit through these gaps and leach into the blood. This activates an inflammatory response in the body.

Usually the body can easily clean up this sort of bacteria leaching. Only under heavy duress the body can be overwhelmed. This can occur in extreme exercise conditions, heat stress, illness and infection.

When the weather is hot, blood flow away from the stomach to the working muscles will be more extreme, so strategies to keep the body cool during training and racing is critical.

The researchers added that repeated bouts of inflammation like this can cause long term fatigue, stomach problems and immune disturbances.

What was interesting was that in both studies, runners who trained sufficiently had higher levels of Interleukin-10, a small anti inflammatory protein that helps offsets negative health effects.

Now you know, make sure you train enough for your race.


Gill SK, Hankey J, Wright A et al (2015). The Impact Of A 24-h Ultra-marathon On Circulatory Endotoxin And Cytokine Profile. Int J Sports Med. 36(8): 688-695. DOI: 10.1055/s-0034-1398535.

Gill SK, Texeira A, Rama L et al (2015). Circulatory Endotoxin Concentration And Cytokine Profile In Response to Exertional-heat Stress During A Multi-stage Untra-marathon Competition. Exerc Immunol Rev. 21:114-128.

Sunday, June 28, 2015

Will Skipping Breakfast Affect Your Race Performance?

Picture by Michael Coghlan from Flickr
Since young, I've been told and have also heard and read that breakfast is the most important meal of the day. It feels like that to me too. Often I'm starving when I get up and I definitely need to eat soon after I wake up.

Research on eating breakfast is mixed though. Lots of studies show that people who eat breakfast regularly tend to be leaner, although this does not mean eating breakfast makes you lean.

Most studies show that skipping breakfast results in lower overall calorie consumption during the day. This may be because you tend to be less active and burn fewer calories.

What if you skip breakfast on race day then? When we sleep, our brain and other vital organs are using carbohydrate to maintain normal body functions. So if you don't eat breakfast, you're bound to be in deficit.

So how would you perform in an evening race if you didn't eat breakfast?

Researchers from Loughborough University in the UK measured exercise performance of a group of cyclists at 5 pm with or without breakfast. The cyclists had to do 30 mins of steady-state cycling followed by a 30 minute time trial.

The cyclists ate as much as they wanted during lunch after skipping breakfast. They had eaten as much as they wanted during lunch since they skipped breakfast (the cyclists ate 200 calories more compared to when they had breakfast).

Despite eating more during lunch when they skipped breakfast, this wasn't enough to make up the deficit.

Their time trial performance was 4.5 percent worse after skipping breakfast.

So if you want to reduce your daily calorie intake, you can skip breakfast, but if you're competing later (even in the evening) it can impair your performance.


Clayton DJ, Barutcu A et al (2015). Effect Of Breakfast Omission On Energy Intake And Evening Exercise Performance. J Med Sci Sports Ex. DOI: 10.1249?MSS.0000000000000702.

My usual breakfast and lunch sometimes

Sunday, June 21, 2015

When Sugar Is Necessary For Runners

Simple sugars (or the white stuff you put in your coffee) generally have a bad rep and are not good for you. You will not believe how your sugar intake adds up easily. It's in sodas and fruit juices, even in bread and salad dressings.

There is evidence that those who consume 25 percent or more of their daily calories as sugar were more than twice as likely to die from heart disease than those whose diets included less than 10 percent added sugar.

Sugar as a simple carbohydrate is necessary for runners, especially if you're running low on fuel while training or racing. Simple sugars are most easily absorbed and processed for fuel. Too much sugar however, will slow absorption.

This means the sugar is trapped in your stomach and does not reach your bloodstream and cells. Now you know why energy gel manufacturers suggest you drink lots of water after your consume energy gels.

You're also aware of the health implications that too much consumption of sugar and not fat causes diabetes.

So how do you balance this information you know now and your need for sugar as fuel?

You need simple sugars when you're doing long, hard workouts or racing in events that last more than an hour. This is when energy gels, sports drinks are absorbed easily for fuel. Numerous studies support this, even the International Olympic Committee's statement for training and competition.

Before training and your races, unprocessed carbohydrates like oatmeal and brown rice work best as they produce sustained energy. You're less likely to bonk or hit the wall as compared to eating donuts, white bread or sugary energy bars.

Sugars that fuel performance during your training/ races are the same ones that get stored as fat when not utilized.

The American Heart Association suggest that you limit sugar intake to no more than 100 calories per day for women and 150 calories per day for men. JAMA, 313(9): 959-960. DOI: 10.1001/jama2014.18267.


Dhurandhar NV and Thomas D (2015). The Link Between Dietary Sugar Intake and Cardiovascular Disease Mortality. JAMA. 313(9): 959-960. DOI: 10.1001/jama2014.18267.

Good during your exercise