How Much Does The Heat Slow You Down?

I was caught in the rain halfway through my run 2 days ago. Since it has been so hot recently, the coolness the rain brought was very welcomed. I also noticed that I managed to run faster with lesser effort. 

So if the heat (and humidity) affects a short run so easily, how much does it affect us when we race?

When running in hot weather, we need more oxygen since some of the blood flow is redirected from working muscles to the skin to cool us down. This requires more energy usage, increases lactic acid production and a higher heart rate at a given pace compared to cooler weather.

Warmer weather can also cause us to fatigue faster by making us sweat more. This can lead to reduced stroke volume, cardic output and blood pressure.

Research has shown that the optimal temperature range for most groups of runners are between 7-15 degrees Celsius (or 44 to 59 degrees Fahrenheit). Below and above this range, marathon finishing times tend to be slower on average.

Most published research studied elite marathoners timings. At the Boston marathon (Miller-Rushing et al, 2012) more than two-thirds of the men and women's course records were set below 13.3 degrees Celsius (56 degrees Fahrenheit). More than a third were set when the temperature was under 9 degrees Celsius (48 degrees Fahrenheit).

The top 10 fastest marathon performances of all time were set when temperatures were between 10-15 degrees Celsius (50 to 59 degrees Fahrenheit). 

However, I found a comprehensive study (El Helou et al, 2012) that included data from the Paris, London, Boston, Chicago and New York Marathons. The researchers found that most non elite runners (finishing times between 3:30 and 5:00 hours) performed best at temperatures around 6.67 degrees Celsius (44 degrees Fahrenheit).

Once the temperature is higher than 15 degrees Celsius (59 degrees Fahrenheit), perceived effort rises and pace slows for most runners. Runners averaging 5:45 min per mile pace slowed approximately 1 second per mile for each 1 degree Celsius (1.8 degrees Fahrenheit) increase in temperature.

You can use this information on race day for your pace. Say you are capable of a 3:30 hrs marathon. You will need to add 2 to 2.5 seconds to your race day pace for every degree above 15 degrees Celcius (59 degrees Fahrenheit).

Those who averaged between 7:25 to 10:00 per mile slowed between 4 to 4.5 seconds per mile for 1degree Celsius (1.8 degrees Fahrenheit) higher than 15 degrees Celsius (59 degrees Fahrenheit).

Optimal running performances for women tend to be at the cooler end of the range (especially for faster female runners. Women tend to be less affected by rising temperatures than men since women (and elite runners) tend to be lighter. They will usually have lower metabolic heat production due to their lower body mass and their higher surface area to body mass ratio. Less energy is then needed to cool the body, this translates to less stress on the cardiovascular system.

Faster runners also spend less time exposed to hotter temperatures (since they finish ealier) which may be a reason they are less affected than slower runners.

The only consolation is that running in the heat does get easier (especially for those of us who live here in Singapore) with repeated exposures to running in the heat (Lorenzo et al, 2010). If you race in a cooler climate, chances of a faster time is much higher.

Organizers of the Singapore International Marathon used to offer a 1 million dollar bonus to world class runners to break the break the world record here. Rumour has it that the organizers (back in 2014) tried to convince Haile Gebrselassie to make an attempt but was turned down immediately after he learnt about our temperature. He did agree to run the 10 km event though and won it.

Now you know that it will never happen. I do not even think a sub 2:10 hrs run will be possible given our heat and humidity.

References

El Helou N, Tafflet M, Berthelot G et al (2012). Impact Of Environmental Parameters On Marathon Running Performance. PLoS One. 7(5): e37407. DOI:10.1371/journal.pone.0037407.

Ely MR, Cheuvront SN and Montain SJ (2012). Neither Cloud Cover Nor Low Solar LoadsAre Associated With Fast marathon Performance. Med Sci Sports Ex. 39(11): 2029-2035. DOI: 10.1249/mss.0b013e318149f2c3.

Lorenzo S, Halliwill J, Sawka M et al (2010). Heat Acclimation Improves Aerobic Performance. J App Physiol. 109:1140-1147. DOI: 10.1152/japplphysiol.00495.2010.

Miller-Rushing AJ, Primack RB, Phillips N et al (2012). Effects Of Warming Temperatures On Winning Times In The Boston Marathon. PLoS One. 7(9): e43579. DOI:10.1371/journal.pone.0043579.

*Note that wind, wet-bulb temperature, dew point, precipitation and cloud cover can affect running performance to some degree. But none of them have more influence than air temperature. 

Keep Jogging Or Rest?

Picture by Richard Seow

For those of you old enough to remember former Singapore runner, Syed Ahmad Taha - he's the last Singaporean runner to run the 10,00m on the track in under 33 mins before Soh Rui Yong in 2012, and Melvin Wong in 2015 at the Singapore SEA Games. Syed ran the 10,000m in 32:41 min in 1990.

I remember watching him do interval training (the original HIIT) at the old National Stadium back in 1988. When I was a teenage runner, those intervals we did certainly did not have such a fancy name like HIIT. You run 15 intervals or repetitions of 400m with a one minute rest in between or the coach will say run 6 x 1km going every 5 minutes (meaning if you run your kilometer in 3:50 min, you get 1:10 min rest before starting again).

Syed Ahmad Taha was doing 25 x 400m with a 60 seconds rest and he would be lying on the track recovering while you could see his heart thumping away. He would spring back up as his coach told him to get ready for the next rep. No super shoes, no super spikes back then in 1990. Respect!

A quick question for all runners before reading the rest of this article. During your track intervals training, do you normally continue to jog/ run after the interval or just rest before starting the next rep?

Well, no prizes for guessing that this post compares active recovery (jog/ run) versus passive recovery (lying down or slow walk) between repeats during interval training.

The study had well trained runners do 4x 2:00 minute at their maximum aerobic speed at an outdoor track, with a 2 minute rest or 2 minute jogging between the intervals.

Resting (rather than jogging during the rest period) enabled the runners to work harder and spend more time at peak VO2. This is the whole point of interval training, to spend more time running in the 90-100 percent VO2 max region. The rest allowed the runners to suffer more. Perceived effort by the runners after each run was also lower with rest in between. The researchers concluded that complete rest is preferable for this type of workout. 

Some points to note. The runs were done at identical running speed. The runners may be able to run faster if they were allowed to run the interval at their own pace with a jog recovery since jogging (low intensity exercise) keeps the blood flowing, which eliminates lactic acid quicker to enable you to go faster at the next rep).

Lactate (or lactic acid) levels were only measured after the workout was over, lactate levels were significantly higher (6.93 vs 6.24 mmol/ L) while the runners rested. 

The question I'm pondering on is whether to make your workout harder or easier? Is standing still to rest better since your muscles are filled with lactic acid and you get to practice running in that state? 

Or is jogging better since you can train your body to eliminate lactic acid quicker form your bloodsteam and thus enabling you to run faster. Perhaps, you can do complete rest while training for your next race this year and do the jogging rest for the same race next year and see which gives a better race timing. Definitely a good study topic for researchers.

If your goal is to run each rep as quickly as possible, then you are better off resting or just walking a little, if the recovery time is a minute or under since resting helps to restore phosphocreatine, which fuels your sprints and the starting stages of your longer runs. (This is why some athletes that require frequent sprints in the sport - hockey, basketball, football etc take creatine) which can be a separate post.

However if your rest period is 2 minutes or longer, light jogging may possibly help you run faster since you are actively clearing lactic acid and other metabolites.

Reference 

Sanchez-Otero T, Tumil JL, Boullosa D et al (2022). Acive Versus Passive Recovery During An Aerobic Interval Training Session In Well-trained Runners. Euro J Appl Physiol. 122(5): 1281-1291. DOI: 10.1007/s00421-022-04926-2.

Does Lactic Acid Affect Your Appetite?

One of our blog's more popular post was regarding lactic acid or lactate. For our new readers, that post came about after a massage therapist asked me if lactic acid in our bodies can form 'crystals' in our muscles with too much running.

A few of his patients who run had gone to this particular massage place and was told by a massage therapist there that 'crystals' left there by the lactic acid/ lactate will affect their running if the 'crystals' are not removed by sports massage.

Yes, lactic acid/ lactate is produced as a by product during intense exercise, but it starts to clear or leave your body once you slow down and especially when you stop your exercise. You do not need help to get rid of it. It certainly won't form 'crystals' in your muscles!

What lactic acid/ lactate does according to recent research is that it can blunt your appetite by altering your appetite hormones (Vanderheyden et al, 2020).

What the researchers in the study did was to have volunteers do an interval workout of 10 x 1 min really hard with 1 min recovery on an exercise bike. They repeated this protocol twice at the same intensity on separate days at least a week apart. For the first time, the participants were given a dose of baking soda and the other time a dose of salt as a placebo.

Baking soda (or sodium bicarbonate) helps to partially counteract rising acidity in your bloodstream during intense exercise (to prevent you from accumulating too much lactic acid in your bloodstream). It is often used as a legitimate and legal performance enhancing drug by some runners (especially middle distance) and track cyclists.

Please note that consuming baking soda can be associated with stomach distress although there was no apparent difference in this particular study.

This allowed the researchers to compare lactate levels in the subjects' bloodstream during and after the 10 x 1 minute intervals since baking soda will decrease lactate levels.

The researchers found that the response of the subjects' appetite hormones were lower when there was more lactic acid/ lactate in the bloodstream.

Ghrelin (which measure hunger levels were lower meaning less hunger) and two appetite suppressing hormones, *GLP-1 and PYY were higher meaning less hunger were indeed different in the two groups during and 90 minutes after the intense exercise.

Previously, when I use to compete and still did really intense training, I definitely do recall that I do not feel like eating after the workout ends. I usually only felt like drinking an ice cold Coke. Well, those were the days .....

What I'm actually wondering is whether changes in our appetite hormones can affect our eating patterns on a long term basis and thus affect weight for serious endurance athletes. If you're training reasonably hard, surely weight isn't gonna be something you worry about.

To conclude, you do not need to flush lactate (lactic acid) out from your body after intense exercise, it starts to dissipate once you stop exercising. Nor do you want to take too much baking soda in a race if you're trying to lower your lactate levels as it can give you stomach distress especially if you haven't tried it in training.


Reference

Vanderheyden LWN, McKie GL et al (2020). Greater Lactate Accumulation Following An Acute Bout Of High Intensity Exercise In Males Suppresses Acylated Ghrelin And Appetite Post Exercise. J App Physiol. DOI: 10.1152/japplphysiol.00081.2020.

*GLP -1 glucagon like peptide-1

*PYY - active peptide tyrosine-tyrosine

Too Much Lactic Acid Causes "Crystals" To Form In Your Muscles?

*What a load of  sh--!

One of my massage therapist asked me today if it's true that with too much exercise, lactic acid can form crystals in your muscles? His friend had been been told by a massage therapist that "crystals" can form in his muscles with too much running and no sports massage to "break the crystals."

This is the 3rd time in two weeks someone asked about this. The first two were my patients.

Apparently they had gone to this particular massage place and were told by the massage therapist there that if "the crystals" in the muscles were not "broken up" it's bad for them and they can't run well. The massage therapist(s) then WhatsApp their patients an article to read.

Now I find this really ludicrous to say the least. I've addressed this issue before. Massage does not flush lactic acid from your muscles.

Any textbook on Exercise Physiology (or you can check online) will explain that you can only accumulate lactic acid in your muscles during intense exercise (e.g. while racing or running intervals). As there is not enough oxygen available, a substance called lactate is formed. Our bodies then try to convert this lactate to energy without using oxygen.

However, this lactate or lactic acid can build up faster in your bloodstream than you can use it. The point where lactic acid starts to build up is called the "lactate threshold." So if you run just below your lactate threshold you won't fill the "burn" in your muscles.

That is what interval training is all about - trying the raise your lactate threshold so you can run at your race pace longer without incurring oxygen debt (or that burning sensation in your muscles).

This "burn" you feel is temporary. Once you slow down and/ or stop exercise, your body can then easily convert the lactic acid to energy. After a short while there isn't any more lactic acid in your muscles. The "burning" sensation in your muscles happen only during intense exercise.

Lactic acid clears very quickly on its own. By the time an athlete has a chance to "use" anything that claims to flush out lactic acid, the lactic acid is probably gone. You don't need help to dissipate it.

Lactic acid definitely does not cause soreness. The soreness you sometimes feel in your muscles a day or two (especially if you've pushed too hard) isn't from the lactic acid accumulation in your muscles. It's most likely delayed onset of muscle soreness or DOMs.

Back to my conversation with my colleague. He then said that his friend said that after a massage session there "to break his crystals" he normally can't run for three days! That's how sore he got. More likely how brutal or how heavy handed the massage therapist was.

When I was still racing, I get sports massage done so I can train/ run long and hard the next day and the day after and after. That's what the sports massage is supposed to do. Helping me to recover better so I can run long and run hard every day if possible. As an athlete, that's what I want to do. If I have to rest three days after a sports massage how do I get my training done?

So be very wary if your massage therapist or even physiotherapist tells you that that you need to "get your crystals broken" or that you need to flush the lactic acid out of your muscles.

*Thanks to my patient for forwarding the article to me.