Time Of The Day When You Are At Your Best

Picture from Healthyplace.com

I have been out of school for decades and have not sat for any tests or exams in quite a while. But I do see new patients almost every day I am working in our clinics. I do take plenty of "tests" too, since every single patient I see will evaluate my treatment and decide if I made them better.

You must be wondering why I am writing about tests this week, Well, the Singapore primary school leaving exams (PSLE) just ended this past week.  Parents whose children just sat for the exams must heave a collective sigh of relief now that it's all over. 

The typical start times for the PSLE oral exams are at 0800 while written exams generally commence at 0815 hours. That's definitely an early start for those taking exams.

Unlike the students sitting for exams, we usually see new patients in our clinic whenever we can fit them in for an appointment. This may not necessarily be the best according to a group of researchers who analyzed the results of over 100,000 oral exams. They found a clear Gaussian distribution (also know as the Normal distribution or bell curve) in pass rates that peaked at noon. 

Passing rate by hour 

Between 11 am and 1 pm is the best time (pictured above). Any earlier or later the chances of passing significantly decreased. In fact the earlier or later in the day these students took a test, the less likely they were to pass.

The reason being our cognitive (or conscious intellectual ability) performance improves over the course of the morning and then declines in the afternoon. We also may have declining energy levels later in the afternoon. If your exam is scheduled later in the day, you may also stress about it and this usually leads to poorer performance.

According to the author's, the examiner's cognitive performance and fatigue level also matters. Both the examiner and student will be at their peak level of performance during the mid day hours.

This all means that whenever possible if you have to take a test or exam, an important meeting or a job interview, you should schedule it between 11 am and 1 pm. It can be the difference between passing and failing. 

Perhaps we should only see new patients in our clinics between 11 am and 1 pm then. 

Reference

Vicario CM, Nitsche MA, Lucifora C et al (2025). Timing Matters! Academic Assessment Changes Throughout The Day. Frontiers Psychol. 16:1605041. DOI: 10.3389/fpsyg.1605041

Training In Hot Conditions Makes You Eat More?

Just after sunrise

After all the rainy days during the first 2 weeks of September, the temperatures were nice and cool. This past week it seems like "someone turned the tap off" and it's been way hotter. 

I weighed myself yesterday morning before and after my regular Saturday ride before work and found that I had lost 2 kg (mostly water) despite eating and drinking more during the ride. These 3 hour rides, when warmer, make me feel like I'm making my body work double time. I've noticed that when the temperature is higher, I need to eat more (during the ride) or else I cannot keep up with my friends.

On Saturday rides that are cooler, I sometimes don't even eat the banana that I bring with me and can still ride well without tiring.

Turns out that training in Singapore's heat and humidity does not just make one more comfortable in hot conditions, it actually changes how our muscles use energy (Xu et al, 2025).

The authors in the study quoted above show that a month of structured heat acclimation training can help change your metabolism to race stronger when it's hot and probably in cooler temperatures too.

The researchers split 18 trained middle and long distance runners into 2 groups. Both groups completed treadmill tests and metabolic assessments at temperatures of 30-32 °C (or 86-89 °F).

The first group trained in normal temperatures (20-25 °Celsius or 68-77 °F). The other group did 20 sessions of heat acclimation over 4 weeks. They ran in tem[eratures between 30-36 °C that pushed their core temperatures to 39-40 °C (or 102-104 °F).

No prizes for guessing that the heat acclimated group made more notable adaptations compared to the control group. Their core temperature during the subsequent treadmill test was lower by 0.4 °C, a clear sign of improved thermoregulation. They were also more efficient aerobically, as oxygen uptake improved by 4 and 3.7 percent at the *first and second ventilatory thresholds.

Plasma volume improved by 4 percent, haemoglobin by 2 percent and erythropoietin by 13 percent after heat acclimation, showing better oxygen support. All signs of heat adaptation.

At submaximal intensities (75 and 85 percent VO2 max, carbohydrate oxidation dropped by 15-19 percent in the heat acclimated group. The runners used less blood glucose and muscle glycogen, using more of the body fat instead. Exactly like I wrote above when I do not need to eat as much during cooler rides. In the picture above, carbohydrate (CHO) use and energy expenditure (EE) before and after control (black bars) and heat training (red).

Upon finishing the treadmill test, the heat acclimated runners cleared lactate more efficiently demonstrating improved recovery.

However, VO2 max did not change, suggesting that having a higher VO2 max (compared to someone else) may not mean you will race faster. The efficiency gains were more beneficial.

Take home message? Those of us who live in sunny and super humid Singapore can train almost all year round in such conditions. A 4 week block of 5 days a week may give you the metabolic edge of using less carbohydrates at higher intensities. This spares your glycogen stores and delays fatigue. The thermoregulatory and blood adaptations will help you stay cooler and deliver oxygen more effectively, especially if you are going to be racing in a friendlier climate. 

You will need to monitor the above parameters and allow for adequate recovery to get the benefits. This is when your blood, sweat (lots of it) and tears will pay off if you do it correctly.

Reference

Xu Y, Ye C, Ma S et al (2025). Four-Week Heat Acclimation Lowers Carbohydrate Oxidation Of Trained Runners During Submaximal Exercise In The Heat. Frontal Physiol. DOI: 10.3389/fphys.2025.1581594/full

*First ventilatory threshold (VT1) is when your breathing becomes noticeably deeper and lactate starts to accumulate in the blood. This indicates a shift from using mostly fat to carbohydrate during exercise.

VT2 or second ventilatory threshold occurs later, this is often when breathing is rapid, more labored leading to a sharp increase in carbon dioxide production. This is when a significant shift to anaerobic metabolism.

Still not too hot

How to Run Faster At The Boston Marathon

Picture from Runnersworld.com

I came across a recently published article detailing the training of 917 runners (495 women, 422 men) who qualified and ran in the 2022 Boston marathon (Lempke et al, 2025). The majority of them finishing in mid-3 hour marathon times. So definitely relevant insights for most serious recreational runners if you want faster marathon timings.

This interesting new study tracked running duration, volume, cross training and changes in training frequency between the last 12 months to 4 months before the race day. Yes, you read correctly, the runners were training 12 months in advance before racing. In addition, training intensity distribution like steady state runs, quality sessions and interval sessions were also analyzed.

Let me highlight the relevant findings. The study found that those who had longer running durations, higher quality ('hard') sessions, running distance and/or volume from 12 months to 4 months before the race was consistently linked to faster timings.

From 12 months to 4 months before the race, those who ran more than 10 hours weekly predicted significantly better performance than 5-7.5 hours, 2.5-5 hours and less than 2.5 hours per week of training (pictured above). For reference, the weekly mileage for the 495 women studied ran 64.4 ± 24 each week while the 422 men studied ran 67.6 ± 26.2 km on average.

Each extra run shaved 3-4 minutes off race time, while each extra quality session was worth 16-17 minutes better timing on average. Running an extra 1 km a week was worth about 3-4 minutes off marathon time.

In the final 4 months to race day, all of the above variables predicted better performance. Runners who included cross training in the final 4 months ran significantly better. Each extra session per week translated to being faster by 6 minutes of finishing time.

Reducing running frequency in the final 4 months improved performance. The runners who decreased their total weekly running sessions averaged 3 minutes faster than those who maintained or increased the frequency of their running sessions.

Just in case you got confused reading the above (I did at first) where the study said adding an extra run each week helps in the final 4 months, but also said a reduction in frequency was associated with better performance (pictured above). 

This means that between 2 runners, the runner running 5 times a week would be faster than another runner running 3 times a week. However, a runner who reduced their runs by 2 runs a week would run faster than another runner who only reduced their runs by 1.

Note that this study was survey based and depended on what the runners recorded in their training logs. Most runners tend to be meticulous about this, I know I was. There was also no mention of what the runners did for cross training. In addition to cycling or deep water running, I also did strength training.

Reference

DeJong Lempke AF, Ackerman KE, Stellingwerrff T et al (2025). Training Volume And Training Frequency Changes Associated With Boston Marathon Race Performance. Sports Med. DOI: 10.1007/s4027-025-02304-4

Rivals Or Brotherly Love

CL and I were rivals (actually more of a team mate as we were friends too) on the track when I was competing in my secondary school's track and field meet. We competed in the 800m, 1500m, 3000m and the 2000m steeplechase events. Though I won all 4 events, knowing CL was also training hard was a powerful motivator and it pushed us both to be better runners.

Yes, having a rivalry with a colleague, friend, or even your sibling can be stressful, but the right kind of competition will elevate each other's performance.

Carlos Alcaraz and Jannick Sinner are currently the top 2 tennis players in the world. They faced each other in 3 of the 4 Grand Slam finals this year including the recently concluded US Open where Alcaraz won. They currently have a super rivalry and their duels definitely push each one to higher heights. Just like Rafael Nadal and Roger Federer (pictured above) before them.

Research has shown that rivalries can have perks. One study showed that runners ran almost 5 seconds faster per kilometre in a race when a runner whom they considered a rival was also racing.

Another study showed that when different NCAA, NFL, NBA, and MLB team performances were analyzed, when a team's rival beat them in the post season one year, that same team does better the next year.

Of course there are occasions when rivalries can hurt us. One study showed that people can be unethical or even ruthless when competing against a rival because they really want to win.

A big difference between rivalries that boost us versus those that hurt us is whether they are viewed as long term relationships. Nadal and Federer are real friends after they step off the court after trying their hardest to beat each other on court. Federer wrote a moving tribute to Nadal just before his last tournament. Nadal did the same for Federer just before the latter retired too in 2022. 

It appears that Alcaraz and Sinner too have an underlying friendship besides their rivalry.

Picture from Cyclinguptodate.com

This is very much like what currently happens in cycling too. Current world cycling champion and 4 times Tour De France winner Tadej Pogacar is very friendly with his rivals, even driving to a race (Milan San Remo) together. 

Pogacar and Vingegaard

This was highlighted in a viral podcast by Lance Armstrong. Some cyclists may agree with Lance, but it's probably the character of Pogacar, Mathieu van der Poel and Jonas Vingegaard etc to be friendly and get along. That is definitely acceptable and touching even.

So, you do not have to be buddies with your rival, but surely you can be friends and have mutual respect for each other. Wish each other well and do your best to beat the other and this may help both of you soar to higher heights.

References

Kilduff GJ (2014). Driven To Win: Rivalry, Motivation And Performance, Soc Pysch Per Sci. 5(8): 944-952. DOI: 10.1177/1948550614539770

Kilduff, GJ,  Galinsky AD, Gallo E et al (2016). Whatever It Takes To Win: Rivalry Increases Unethical Behaviour. A Manag J. 59(5): 1508-1534. http://www.jstor.org/stable/26157371

Pike BR, Kilduff GJ & Galinsky AD (2018). The Long Shadow Of Rivalry: Rivalry Motivates Performance Today And Tomorrow. Psych Sci. 29(5): 804-813. DOI: 10.1177/0956797617744796

Girls Get A Lot More Anxious Than Boys

Picture from Motherwellmag

In a first of its kind study, Prof Setoh and colleagues from Nanyang Technological University found that girls are a lot more anxious than boys. This happens between the ages of 8.5 and 13 years when they go through a sharp spike in social anxiety. They fear being judged negatively in social situations.

By the time they turn 13, their social anxiety levels are significantly higher than boys. If untreated, this may lead to poor mental health and interpersonal relationships. Academic and work performance later in life may be affected as well.

The article was just published on 300825 in the Research On Child And Adolescent Psychopathology. The Straits Times also published an article on it on 010925.

ST 010725

You must be wondering why I chose this topic this week, or wondering about my credentials on adolescent mental health. 

Just after I came across the newspaper article, I remembered a recent study by Lundgren et al  (2025) on how physical activity during certain periods can protect children from developing depression, anxiety and addiction. Their study was based on a large group of Swedish children followed from birth until their 18th birthdays. The long time frame allowed comparison between parent-rated levels of activity to diagnoses from a national registry. This is to eliminate pre existing issues that caused low activity levels or transient dips that were interpreted as social anxiety issues.

The study involved 17,055 children, who were born between 1997-1999. The parents had to rate various aspects of their child's health at 5, 8 and 11 years. Activity levels were tracked separately for school days and non school days. Participation in organized sports were tracked at 11 years and reported in hours per week.

The authors found that physical activity (reported by parents) declined from 4.2 to 2.5 hours each day between 5 and 11 years of age. Analyses showed that boys and girls had different outcomes and patterns. 

Time outdoors showed no protective associations while participation in organized sports at 11 years of age showed significant protective effects on anxiety and addiction for both boys and girls and on depression for boys. The authors concluded that his study provides evidence that physical activity and participation in organized sports may have protective effects against several adolescent mental health diseases.

Possibly policymakers working to control vaping in Singapore could use this information?

Access to the articles at the links below.

References

Lundgren O, Tigerstrand H, Lebena A et al (2025)Impact Of Physical Activity On The Incidence Of Psychiatric Conditions During Childhood: A longitudinal Swedish Birth Cohort Study. BJSM. 1:59(14): 1001-1009. DOI: 10.1136/bjsports-2024-108148

Tng GY, Law ECChen HY et al (2025). Developmental Trajectories Of AnxietySubtypes From ChildTo Early Adolescence: The Role Of Parenting practices And Maternal Distress. Res Ch Adoles Pysch. DOI: 10.1007/s10802-025-01364-4 

Can Too Much Running Increase Colon Cancer Risk?

Just when I'm reading about Ultras

If you've read a previous post of mine you know that there is evidence showing that people who are physically active have a lower incidence of cancer. A 2016 meta-analysis of 52 prospective studies found physically active adults were 24 percent less likely to have colon cancer compared to sedentary peers.

So I was very surprised when I came across a poster presentation that suggested that those who do high volume ultra marathon and marathon running may actually have an increased risk of advanced pre-cancerous colon lesions. The New York Times wrote about this too.

Researchers had 100 long distance runners ranging from 35 to 50 years who completed at least 2 ultramarathons (> than 50 km) or 5 marathons. These runners underwent screening colonoscopies, with all polyps reviewed by a team of oncologists, pathologists and gastroenterologists. 

They were found to have polyps (> 10mm with  tubulovillous features) that were more likely to turn into cancer compared to the general population (40-49 years old). 15 percent of the 100 runners had advanced adenomas. This was greater than 10 times higher than the benchmark. 39 runners had at least 1 adenoma of any type.  Prevalence in the matched general population was just 1.2 percent.

Most cases happened in runners with very high training exposure (pictured above), multiple ultramarathons or completed more than 15 races. There were even a few cases of high grade dysplasia, just 1 step away from colorectal cancer.

The researchers' hypothesis was that due to extremely high volume distance running, this leads to repeated low blood flow to the gut leading to chronic injury and inflammation. This can repeatedly injure the stomach lining. This recurring pattern may then accelerate carcinogenic changes that lead to the development of pre-cancerous adenomas.

Moderate exercise does lower systemic inflammation, but ultra marathon training can increase inflammation in the gut made worse with frequent high volume racing. This worsens during intense exercise in the heat. Since chronic gastrointestinal stress impairs absorption of fibre and micronutrients that normally protects the colon, their findings may be reasonable. More so if recovery isn't adequate.

The difference compared to the normal population does cause some concern. However, do note that this is a relatively small study done only in 1 location. There is no proof of causation, genetics, nutrition and other lifestyle factors that may also play a role. 

For most of us runners, running is protective against colon cancer, and does not increase our risk to it. I do not have any patients who run >2 ultra marathons or more than 5 marathons a year. If they do, then their risk profile may (emphasis on may) be higher. 

So if you do log mega mileage, race often and are concerned about your cancer risk, it may be wise to get colon cancer screening particularly if you have persistent gastrointestinal symptoms.

Do wait for the full peer review study to be published before making any final conclusions.

Reference (for the abstract)

Cannon TL, Bonomelli S, SwainWR et al 92025). Risk Of Pre-Cancerous Advanced Adenomas Of The Colon In Long Distance Runners. J Clin Oncology. 2025 ASCO Annual Meeting. 43(16) suppl. DOI: 10.1200/JC0.2025.43.16_suppl.3619

Are You A Fast Or Slow Walker?

Let's go for a walk

Walking seems like such a simple thing. We usually do not think about it until you cannot walk properly. My patient who had a recent ACL reconstruction literally had to learn how to walk again Pictured below).

Walking actually relies on quite a few body systems working together. Your eyes to help you see where you are going.  Your muscles and bones working together to get you places, your heart and lungs to circulate oxygen. Of course you need your brain and nerves to coordinate everything.

Previous studies have shown that walking speed is a significant predictor of life expectancy in older adults. Pooled results from 9 studies involving 34,000 adults aged 65 and older showed that walking speed was significantly associated with lifespan. Men with the slowest walking speeds at age 75 had a 19 percent chance of living for 10 years compared to those with the fastest walking speeds who had 87 percent chance of survival.

Another study found that even amongst healthy adults aged above 65, participants with slower walking speed were 3 times more likely to die of cardiovascular disease compared to those who walked faster.

Did you know that if you are a slow walker you may have a smaller brain compared to a faster walker? Research has shown that how fast you walk to the shops, MRT, or your local coffee shop can predict your chance of a heart attack, being hospitalised or even dying. Your walking speed can even reveal your rate of cognitive ageing.

As we age, these systems start to slow down. Studies show that walking speed is a significant predictor of life expectancy in older adults. This does not just apply to older adults as Rasmussen and colleagues (2019) found that even amongst 45 year olds, a person's walking speed can predict the rate at which their brain and body were ageing.

In that study (Rasmussen et al, 2019) had 904 subjects, all 45 years old born between 1972 and 1973 living in New Zealand. Their health and cognitive function were assessed regularly over their entire lifespans. 

There was fairly huge variation in walking speed among the subjects. You would think that these 45 year olds would have similar walking speeds but some walked as quickly as healthy 20 year olds while others walked as slowly as much older adults.

The 45 year olds with slower walking speeds showed signs of "accelerated ageing" with their lungs, teeth and immune systems were in poorer shape compared to those who walked faster. They also had 'biomarkers' associated with a faster ageing rate such as higher blood pressure, raised cholesterol and lower cardiorespiratory fitness. 

The slow walkers also had a weaker hand grip strength and found it more difficult to get up from a chair. Other signs of cognitive ageing include lower IQ test scores, worse memory test scores, processing speed, reasoning and other cognitive functions. MRI scans showed they had smaller brains and a thinner neocortex - the outermost brain layer which controls thinking and higher information processing.

Even the faces of the slow walkers were rated as ageing faster than the faster walkers!

The research suggests that the slow walkers' brains and bodies age at a faster rate compared to the quick walkers. There were already signs that these health differences were present from an early age  as researchers were able to predict the walking speed 45 year olds based on intelligence, language and motor skills test taken when the participants were just 3 years old. 

Wow, I am so surprised that there is a link between how fast people walked at 45 years old and their cognitive abilities all the way back to when they were 3 years old. Perhaps walking speed is not only a sign of ageing but a clue to lifelong brain health.

Reference

Rasmussen LJH, Caspi A, Ambler A et al (2019). Association Of Neurocognitive And Physical Function With Gait Speed In Midlife. JAMA Netw Open. 2:2(10): e1913123. DOI: 10.1001/jamanetworkopen.2019.13123.