Coffee's Performance Enhancing Powers

I remember reading about how drinking coffee can help improve sporting performance in endurance races when I was 17 and competing in track and field races back then. I was not a regular coffee drinker then (nor now). I made myself a cuppa before a track race held at the NUS track (1500m) and ran a personal best!

Back then, I read that the caffeine in coffee was a stimulant and that it enhanced fat burning to give nuscles more energy. Another theory was that caffeine acts in the brain to make  physical exertion feel easier (by blocking receptors that detect adenosine, a molecule that detects fatigue). This also helps in all out bursts of strength, prolonged endurance and cognitive effects like enhanced attention and vigilance.

Fast forward to a recent study that involved cyclists who completed time ridden to exhaustion tests at a predetermined intensity. They could sustain that intensity for around 5 minutes on 9 separate occasions. They were wired up with electrodes and other equipment before and after the rides to assess brain function, circulatory system efficiency and muscle function.

The cyclists did similar rides each time. Either 5 miligrams per kilogram body weight of caffeine was ingested an hour before the ride, or a placebo was taken. In some rides, they stopped the ride prematurely at either 50 percent or 75 percent of the time achieved in the baseline test to assess mid ride neuromuscular function.

In the final ride, the riders were given caffeine but were stopped at the exact time they had given up in the previous placebo trial to get a similar comparison of the effects of riding at a given power for a given duration with or without caffeine.

Here's a summary from the fairly complex analysis by the authors. Caffeine works! The cyclists lasted 14 percent longer (5:55 min) with caffeine compared to the placebo (5:14 min). This is equivalent to a 1 percent gain if the riders did a race or time trial.

Caffeine did help the muscles delay loss of power. Those taking the placebo at the 75 percent mark of the test had lost 40 percent of muscle power compared to less than 35 percent for those who had taken caffeine. At exhaustion those taking the placebo could generate only 60 percent less force than when they were fresh. With caffeine, the loss was 45 percent at the exact same time, pace and power.

The brain (or central nervous system) sent weaker signals to get the muscles to work when the cyclists got more tired when they ingested the placebo. With caffeine, the signals never declined, even when the cyclists reached exhaustion. Their brains were still enthusiastically getting their muscles to contract.

Caffeine also kept oxygen flowing through their arteries, as measured by a pulse oximeter attached to the cyclists' right fingers. There was only a mild decrease at exhaustion compared to a steady decline seen in those who took the placebo. The authors suggested that having more oxygen available may be one of the reasons the muscles kept working better during caffeinated rides.

This study also shows that caffeine also reduced perceived effort - just like what I read when I was 17. The pace you're holding definitely seems easier.

For those of you that are keen to try caffeine, the authors suggest 3 to 6 milligrams of caffeine per kilogram of your body weight taken an hour before your event starts. Higher doses may speed up your heart rate, not what you need during your race. Regular coffee drinkers may get a slight gain if you stop drinking coffee for a week to get that boost.

Reference

Cristina-Souza G, Santos PS, Santos-Mariano AC et al (2022). Caffeine Increases Endurance Performance Via Changes In Neural And Muscular Determinants  Of Performance Fatigability. Med Sci Sports Ex. 54(9): 1591-1603. DOI: 10.1249/MSS.0000000000002944

Does Dynamic Stretches Help Running Performance?

Our new physios doing the dynamic stretches

Previously I had written that performing any static stretches before exercise or competition can be detrimental to your athletic performance. Studies have also shown that doing static stretches before competing or exercising is more likely to cause an injury. In fact, performing just one static stretch of 30 seconds can reduce your maximum strength.

Meanwhile, fitness professionals, coaches and other studies have suggested performing dynamic stretches as an alternative warm up to static stretches instead.

Well, this published study had runners do both. An initial assessment was done to get the runners VO2 max levels. The researchers had a group of well trained university runners do a general warm up (GWU) on one day versus doing a general warmup (GWU) plus dynamic stretching (DS) before getting them to run until exhaustion on a treadmill on another day.

The GWU consisted of running on the treadmill at a speed equivalent to 70 percent of each runner's VO2 max for 15 minutes. Each runner then did a standing rest for 5 minutes. This was followed by the run to exhaustion on the treadmill at a speed equivalent to 90 percent of their VO2 max. 

When doing the GWU plus DS, dynamic stretches were done for all the lower limb muscle groups (10 reps each), see picture below. That took 3 min 45 seconds in all. After resting for 1 min 15 seconds, the runners started their run to exhaustion on the treadmill at a speed equivalent to 90 percent of their VO2 max. 

Well, this published study had runners do both. An initial assessment was done to get the runners VO2 max levels. The researchers had a group of well trained university runners do a general warm up (GWU) on one day versus doing a general warmup (GWU) plus dynamic stretching (DS) before getting them to run until exhaustion on a treadmill on another day.

The GWU consisted of running on the treadmill at a speed equivalent to 70 percent of each runner's VO2 max for 15 minutes. Each runner then did a standing rest for 5 minutes. This was followed by the run to exhaustion on the treadmill at a speed equivalent to 90 percent of their VO2 max. 

When doing the GWU plus DS, dynamic stretches were done for all the lower limb muscle groups (10 reps each), see picture at the top. That took 3 min 45 seconds in all. After resting for 1 min 15 seconds, the runners started their run to exhaustion on the treadmill at a speed equivalent to 90 percent of their VO2 max. 

The results showed that the GWU plus DS group lasted significantly shorter (10:40 min)  than the group that just did the GWU (12:40 min). Distance covered was between 2.3 to 5.4 km.

The authors of this study were hypothesizing that performing GWU plus DS may help improve endurance running performance. Unfortunately the results indicated otherwise. 

Another study by the first 3 authors (Yamaguchi et al, 2015) showed that performing the same five DS (10 reps) followed by a rest period of 1 min 23 secs actually prolonged the run time to exhaustion (an extra 18.2 percent) compared to a sit down rest. Run to exhaustion on the treadmill was also done at a speed equivalent to 90 percent of their VO2 max.

What is good about this study was that there was real attention to detail. The testing was done during the off season for the runners so no prior vigorous training was done. The runners were also asked to avoid performing intense exercises or training on each test day and the day prior. 

The runners were also instructed to have similar meals and drinks on the test days and previous day and to finish any meal 2 hours before running. Runners were also asked to avoid alcohol the day before running and caffeine on the test day. Each runner wore the same attire for the test runs and performed the test at the same time of day in consideration to circadian rhythm. The laboratory temperature was kept constant at 20-24 degrees Celsius throughout. In short, the authors tried to keep everything else constant other than the warm up. 

What wasn't as good? Bear in mind that the study only had 8 runners. They are definitely fast runners (looking at their profile), but the sample size is small. The rest period after the dynamic warmup was also extremely short (150 seconds). Fatigue after the DS was attributed by the authors as the cause for worse performance.

When I was competing in events like 1500m - 5000m on the track, I'll do a rather languid jog of 2-3 km to warm up followed by some limbering movements to loosen up. This was followed by repeating some striding (or goal pace running) 5-8 times for 150-200 meters. Then it would be resting and waiting for our event to start. Definitely longer than 1 minute 15 seconds before racing. Definitely did not do any sort of stretching then.

My advice would be to try out dynamic stretches or whatever that is new (shoes, bike, run technique etc) in your off season, not before an important competition, to see if it would be something that might work for your body. Most importantly, do what works for you. Every body is different.

References

Yamaguchi T, Takizawab K, Keisuke S. (2015). Acute Effect Of Dynamic Stretching On Endurance Running Performance In Well-trained Male Runners. J Strg Cond Resc. 29: 3045-3052. DOI:10.1519/JSC.0000000000000969

Yamaguchi T, Takizawab K, Keisuke S et al (2019). Effect Of General Warm-up plus Dynamic Stretching On Endurance Performance In Well-trained Runners. Res Quart Ex and Sport. 90(4): 527-533. DOI: 10.1080/02701367.2019.1630700.

*thanks to Thiviyan and Rashid Aziz for getting me the articles

Definitely No Bull

Energy drinks on offer - you buying?

My previous article on energy drinks like Red Bull was one of the more popular articles the year I wrote about it. Many readers commented that they were not aware how bad energy drinks were. In fact, the World Health Organization issued a statement calling energy drinks a potential danger to public health.

Now it seems that there may be more reasons to avoid energy drinks.

A recently published article suggest that caffeinated energy drinks can also raise blood pressure and alter your heart's electrical circuit.

That is definitely not surprising considering there was a case report showing atrial fibrillation (or abnormal heart rhythm in a 14 and 16 year old boy) and even a case of heart attack in a 19 year old previously after consuming energy drinks

The researchers tested two groups of healthy people between the ages of 18-40.  One group drank energy drinks that can be easily purchased containing 304-320 milligrams of caffeine while the other drank a placebo drink consisting of lime juice, carbonated water and cherry flavoring.

The participants drank 946 ml (or 32 ounces) of either one of those drinks on three separate days while researchers measured their heart's electrical activity and blood pressure. Measurements were taken before they drank, twice within the hour that they drank the beverage and four hours after.

Now, you'll be shocked to read that they group that drank the energy drink showed higher QT intervals up to four hours later. The QT interval is the time it takes the lower chambers of your heart to prepare for a beat. In general, the normal QT interval is below 0.4 to 0.44 seconds. If the interval is too short or long, it can cause arrhythmia. This is a condition where the heart beats abnormally.

Other than the change in QT intervals, those that drank the energy drink had a significant increase in systolic and diastolic blood pressure.

Coffee lovers will be glad to know that the researchers do not think that caffeine is the main culprit for the increase in QT interval. It may be the caffeine in combination with the other ingredients like sugar, high fructose corn syrup, artificial sweeteners and non nutritive stimulants like guarana, ginseng taurine, L-carnitine, inositol, verba mate and D-glucuronoalactone that caused the changes.

The researchers cautioned the elderly, young children and those of you who have underlying long QT intervals, hypertension and taking antibiotics and anti-arrhythmic medication to be careful with consuming energy drinks.

Also, consuming a few cans of the energy drinks can certainly exacerbate those with underlying heart conditions or those taking certain heart medications.

Reference

Shah SA, Szeto AH et al (2019). Impact Of High Volume Energy Drink Consumption On Electrocardiographic And Blood Pressure Parameters: A Randomized Trial. JAHA. 8(11). DOI: 10.1161/JAHA.118.011318.

Now that's a lot of bull you do not want

Which Drink Hydrates You Best?

Ever wondered which drink is best after a hard training session or race? I've written before that as a recovery drink, chocolate milk is as effective as Gatorade and even superior to Endurox.

Quite a few factors affect how quickly you pee out a certain drink. Drinks with more calories or electrolytes tend to stay in your system longer. How much you drink at a time also plays a part according to an article I read.

Researchers recruited 73 subjects to test 13 different drinks. Each subject tested water and three other beverages. At each session, the subjects drank a litre of the chosen beverage and collected their urine for the next four hours.

A "beverage hydration index" showed how much of that drink was retained after two hours compared to a litre of water.

Picture from American Journal of Clinical Nutrition

Looking at the picture above, you can see that a higher bar means more fluid retained. The dotted line represents twice the coefficient of variation away from water (meaning you can be real sure of a positive result).

The chart shows that milk stays longer in the body probably because of its calorie content. Milk and an oral rehydration solution (or sports drink, due to its calories and sodium) also stays in your system.

Personally, I was quite surprised that tea, coffee and beer did not seem to produce significantly more urine.

In fact coffee seems to have the lowest reading in the chart. The authors suggested that the diuretic properties of alcohol may be counterbalanced by its retention promoting calories (although another previous study that compared regular and alcohol free beer showed that regular beer drinkers had 12 percent more urine).

The authors also pointed out that larger doses of caffeine or alcohol may trigger more urine

Well, now you know not all drinks take the same time to reach your bladder. Choose your drinks wisely after your hard training session or race.


Reference

Maughan RJ, Watson P et al (2016). A Randomized Trial To Asess The Potential Of Different Beverages To Affect Hydration Of Different Beverages To Affect Hydration Status: Development Of A Beverage Hydration Index. Am J Clin Nutr. 103(3): 717-723. DOI: 10.3945/ajcn.115.114769.