Sunday, May 28, 2023

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.


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. 

Sunday, May 21, 2023

Do Orthotics Reduce Kneecap Loads In People With Knee Pain?

Many of our patients wear insoles (or orthotics) as they have been told that it 'corrects' their flat feet while helping to reduce excessive forces on their patellofemoral (kneecap) joint. This then helps to prevent kneecap pain.

Customed made orthotic
Well, if you have been told (by your health professional) that you need insoles/ orthotics for the same reasons, now you can tell them that this latest published systematic review/ meta analyses from the BJSM suggests otherwise. This is a very important study since kneecap pain is very commonly seen in in our clinics (and many others) affecting both the young adolescents and older adults. 

The authors identified 33 eligible studies and did 3 different comparisons during walking and running combined. Using insoles/ orthotics with medial (arch) support versus no insoles, minimalist shoes versus conventional footwear and lastly rocker versus non-rocker footwear.

Arch supports
Analyses by the authors showed that insoles/ orthotics that support your medial arches DID NOT alter kneecap loads during walking or running. This questions results from previous research that suggests the pain reducing effects of insoles/ orthotics. The reduction in pain may have been due to other influences and not the reduction in kneecap loads.

Results also show that mimimalist type footwear reduced peak kneecap loads when compared to conventional footwear during walking and running combined. This systematic review demonstrated an average 9.5 percent reduction in kneecap load in minimalist type footwear compared to conventional footwear over a run of just 1 km. This translates to 1,462 kg for an 80 kg person. This is clinically relevant considering the cumulative load reduction that can occur over numerous loading cycles during running.

I've written about this known fact many times over the years. Using results from Daniel Liberman's study (2010), runners who land correctly in their running technique will have benefits as impact is a lot less (even less than landing on your heels with cushioned shoes on).  If you land wrongly (with minimalist type shoes) the impact is 7 times greater thus greatly increasing the chance of injury. See picture below.

Because kneecap loads are reduced, they are transferred to the ankle and foot bones leading to fractures in the foot bones especially when you do too much too soon. Hence, correct technique and patience is crucial using minimalist type footwear. This is why many podiatrists say minimalist type footwear is not good (for you) since they cause foot  and metatarsal fractures, but bear in mind podiatrists also cannot sell you orthortics to place in your minimalist type footwear. 

You have also never seen Kipchoge or any elite marathoners wear these minimalist type shoes in a race. The body's muscles will not be able handle absorbing the load (while wearing minimalist type shoes) while running at the high intensities at which these races are contested.  They are good for training definitely, but not for racing, especially if you are not patient enough to get used to them. 

Evidence regarding the effect of rocker-soled shoes (see below) during walking and running were uncertain due to limited studies.

Take home message from the researchers is that minimalist type footwear reduces kneecap loads compared to conventional footwear in people with or without kneecap pain during running. 

Insoles/ orthotics that support the arches do not alter kneecap load during walking or running. Now you know for sure.


Liberman DE, Venkadesan M et al (2010). Foot Strike Patterns and Collision Forces in Habitually Barefoot Versus Shod Runners. Nature. Jan 463(7280): 531-535.

Kayll SA, Hinman RS, Bryant AL et al (2023). D Biomechanical Foot-based Interventions Reduce Patellofemoral Joint Loads In Adults With And Without Patellofemoral Pain Or Osteoarthritis? A Systematic Review And Meta-analysis. BJSM. DOI: 10.1136/bjsports-2022-106542

MBT rocker-sole shoes
*Thanks to Hui Meng for getting me the article

Sunday, May 14, 2023

Does Eating Fried Food Make You Anxious Or Depressed?

I have a weakness for french fries, I can eat them for all my meals and not get sick of it. Hence, I was not happy when I read that high fried food consumption (particularly potatoes) can affect your mental health.

This recently published study studied data on depression, eating patterns and anxiety levels on eating patterns of 140,278 people collected over 11 years. Subjects diagnosed with depression in the first 2 years were excluded. Follwing that, the researchers found 8,294 cases of anxiety and 12,735 cases of depression in people who ate fried food.

All in all, the researchers found that people who regularly ate fried food (particularly fried potatoes like french fries) were 12 percent more likely to be anxious and 7 percent higher risk of depression compared to those who did not eat fried food. Those who ate fried potatoes had a 2 percent higher risk of depression than those who eat fried chicken (white meat). The associations were more pronounced among male and younger consumers.

The researchers suggested that a chemical called acrylamide formed during frying is responsible for the higher risk of depression and anxiety. This affects the brain lipid (fat) metabolism and affects permeabilty of the blood brain barrier inducing stress mediated neuro (brain) inflammation

An earlier study on 715 Japanese workers (Yoshikawa et al, 2016) also found that there was a "significant positive indirect association" between eating fried food and experiencing depression. The Japanese authors concluded that "frequency of fried food consumption was associated with lower resilience to depression".

I need to point out that the researchers did not prove that eating fried food actually caused anxiety and depression. They merely found a link between eating fried food and an increased risk of anxiety and depression.

The researchers also did not determine whether people were more likely to become anxious and depressed from eating fried food or because they ate fried food when they were feeling down. We all know that fried food is comfort food for many people. People who are feeling anxious or depressed may turn to fried food for comfort.

People who are feeling down and depressed may also have less energy to prepare their own meals. They may then resort to easy and fast (fried) food as do people with overwhelmingly busy schedules. High trans fat in fast food is linked to inflammation leading to mood disorders. Being low in nutrients, fried food also contributes to poor overall diet quality.

So, are we supposed to consume less fried food? Eating too much fried food affects your gut (stomach) microbiome and when your gut does not feel great, it affects your physically and emotionally. 

We definitely need more research to look at how food, weight, diet, mood and other factors interact and affect us. For now, I will continue to eat french fries, but in much smaller amounts.


Wang A, Wan X, Zhuang P et el (2023). High Fried Food Consumption Impacts Anxiety And Depression Due To Lipid Metabolism Disturbance And Neuroinflammation. PNAS. 120(18) e2221097120. DOI: 10.1073/pnas.2221097120.

Yoshikawa E, Nishi D and Matsuoka YJ (2016). Association Between Frequency Of Fried Food Consumption And Resilience To Depression In Japanese Company Workers: A Cross-sectional Study. Lipids Health Dis. 15:156. DOI: 10.1186/s12944-016-0331-3.

Thursday, May 11, 2023

Team Building Event

At first some members of our team suggested trying laser tag for our team building event this quarter. However, after some discussion, we decided to go bowling for our team building event this morning instead. 

Reckon we can be 'professional' bowlers? Have a look.

Of course we got hungry and had lunch together. 

We also celebrated Bryon's birthday (it was yesterday). 

Guess how young he is?
We missed Aized who was not feeling well this morning. Get well soon. Stay tuned for the next team building session.

Sunday, May 7, 2023

Why Agility Matters

I recently had a patient who was was hit by an oncoming skate scooter. Remember when e-scooters and other mobility devices were really popular before being banned for causing too many accidents? They were a nuisance along pedestrian sidewalks where I live and probably everywhere else. 

See who catches it first
I was explaining to her how she needed some agility training to avoid a similar situation. Chances are if she was more agile, she would have had a higher chance of avoiding that skate scooter. 

Agility balls
Agilty is defined as a quick whole body movement with a change in speed or direction in response to a stimulus. Being agile means being able to start, stop, move, hold and quickly change your position.

For example, when you have friend near you who accidentally drops a pen (or worse, their phone), you react quickly to help them catch it. That means you can able to respond quickly to environmental cues. Like moving quickly out of the way on the pedestrian path when a cyclist suddenly swerves into your walking or running path. Being agile (or nimble) can help ward off injury for athletes and non athletes alike. With this skill, you can stay 'forever' young.

Don't mistake agility for speed as agility requires sharper reactions as well as smoother movements. You definitely need speed when running to reach the ball while playing tennis, but agility is what helps re-establish your on court position to prepare for the next volley or drop shot. 

While speed is definitely part of agility, it does not include mutidirectional changes and real time decision making processes. And that is critical to getting ahead in many sports, and in life too.

Other than speed, muscle strength and power as well as stability are important in agility. They also help with activities of daily living like getting the laundry, getting in and out of your car or walking on uneven ground since all of the above needs spatial awareness and physical control.

Agility also engages your brain since it requires mental acuity and awareness. So even non athletes need agility to ward off falls. You need to be mindful of your movement and not just be on autopilot. This helps to reduce the risk of injury as well as prevent falls since you are both mentally and physically spry.

While playing on court or field, agility can determine how a player reponds to different manoeuvers or reacts to an opponent. It can mean being beaten to the ball or scoring the winner. In all ball sports, anterior cruciate ligament (ACL)injuries most often occur during sudden deceleration and change of direction movements. So agility related training can decrease incidences of injuries. This could be the difference between staying healthy or getting injured.

For my patient, I would get her to do some work with deceleration first, to enable her to learn how to absorb impact and stabilize her body. Following that, we can work on agility. I normally get her to practise movements in 3 planes of motion. The sagittal plane (left and right), the transverse plane ( this divides the body into top and bottom sections) and the frontal plane (forward and backward movements).


Sheppard JM and Young WB (2006). Agility Literature Review: Classifications, Training And Testing. J Sp Sci. 24(9): 919-932. DOI: 10.1080/02640410500457109.

Monday, May 1, 2023

How Credible Are Online Fitspiration Accounts?

Lots of fitness influencers have sprouted up especially during Covid-19. They often have photographs and videos showing you how they exercise in the latest fitness fashion attire and accessories. They are also fit-looking, tanned and toned. Popular fitness inspiration hash tags on Instagram include #fitspiration and #fitspo. They appear in more than 100 million posts.

I do not have an Instagram account but if you do, try scrolling through #fitspiration or #fitspo  and you can see lots of thin, athletic women (and men) promoting fitnessexercise and healthy lifestyles.

These 'fitspiration' accounts by health and exercise influencers usually post content to empower other individuals to pursue healthy lifestyles. 

Since so many people look to social media (such as Instagram and TikTok) for information and motivation to exercise, we need to be mindful of the content being presented. How legit are these fitness influencers?

Personally, I feel it is inspiring and easier to get motivated when someone shares his/ her inspirational photos, videos, quotes etc on fitness and health

However, research from Adelaide, South Australia (Curtis et al, 2013) found that nearly 66 percent of the top 100 influencers put up dubious fitness information. 25 percent presented hypersexualized content, nudity, as well as potentially harmful or unhealthy content. Some of these influencers also degraded others.

Many of the accounts promoted unrealistic or unhealthy body shapes with a strong focus on ultra fit, lean and slim physiques. This implies that only thin and toned bodies are considered healthy and beautiful.

A lack of reliable, credible health and fitness content on a platform like Instagram which has more than a billion users all over the world is concerning since body image and self esteem are so important.

So much focus on outward appearances can drive unhealthy reasons to exercise and diet, leading to unhealthy body image issues and concerns.

That same study (Curtis et al, 2013) from South Australia developed a reliable audit tool to help identify credible and non credible fitness and health Instagram accounts. Credible fitspiration accounts can help promote correct participation in exercise and fitness activity. 

Looking for some inspiration to exercise? Make sure you screen the influencers that you follow. You can find the evidenced based audit tool at the end of the article.


Curtis RG, Prichard I, Gosse G et al (2023). Hashtag Fitspiration: Credibility Screening And Content Analysis Of Instagram Fitness Accounts. BMC Public Health. 23,412. DOI: 10.1186/s12889-023-15232-7