Sunday, July 25, 2021

4 Exercises To Avoid If You Have Shoulder Pain

We've seen quite a few patients in our clinic recently with shoulder injuries after exercising at gyms. Often, the patients will ask how soon they can get back to their regular gym exercise routine. 

I haven't found any published evidence for what I'm suggesting. They are based purely on my personal observations, treating many patients with shoulder pain and of course doing the same exercises myself.

So here are a few exercises to avoid in the gym (at least until the pain ceases) if you currently have shoulder pain.

First up is the behind neck Lat (Latissimus Dorsi) pull downs. The bar behind the head position potentially creates a situation where the humerus (arm bone) can move too much in front. Majority of the time, it is due to lack of scapular retraction. This creates a scenario whereby they need more than average shoulder extension to get their elbows behind the body so the bar  can clear the back of their head. This places high loads on the front of the shoulder  and can potentially damage the anterior glenohumeral ligaments and the Biceps Brachii tendon. 

Next is behind the neck shoulder press. This is similar to the Lat pull down, but more damaging. When pressing up, the Deltoid muscles have to work, whereas during a pull, the Latissimus Dorsi works. The Deltoid abducts the shoulder and also elevates the humerus into the acromion process. So a pulling movement with the Latissimus Dorsi will pull the humerus away from the acromion and reduce shoulder impingement. However, the behind the neck shoulder press can potentially cause shoulder impingement.

The upright row. A lot of people 'cheat' by extending their lower back to get the bar up when the weight is too heavy for them. At the top of the pull, the elbows are in a higher position than the arms putting the shoulders into abduction and internal rotation. This position can cause or worsen shoulder impingement since our shoulder should naturally externally rotate with shoulder abduction. 

Dips. I used to do lots of parallel bar dips as a kid, but I hardly do them now. Try it yourself, when dipping, there are super high tensile loads on the front of the shoulder at the bottom of the dip. The Biceps tendon, anterior shoulder capsule, and Subscapularis tendon are all under huge loads. The scapula is also tilting anteriorly at the bottom of the dip. Much worse if you add weights attached to the waist.

If you do the above exercises occasionally, I'm fairly certain no harm or damage is done. But if done regularly, with high load and especially if you have a pre-existing shoulder dysfunction, they can definitely make your shoulder worse.

Don't get me wrong, the above mentioned exercises are not bad exercises to do at the gym. It's just that some of us do not have the perfect joint placement for certain exercises, due to imbalances and underlying movement restrictions, that makes those exercises damaging.

Sunday, July 18, 2021

About Intervertebral Discs

Picture from M.A. Adams et al, 2010

Having learnt in anatomy class (when I was a physiotherapy student) that our intervertebral discs (IVD) are avascular (has no blood supply), I was instantly surprised when recent research showed that it may not be totally true.

picture from springer link

A little anatomy lesson before I tell you more. Our IVD's are fibrocartilaginous joints that are thought to be the largest avascular structures in the human body. They are made up of three distinct and interdependent tissues. The outer most cartilage endplates are thin layers of hyaline cartilage that anchor the IVD to the adjacent vertebral bones. The vertebral end plates have plenty of blood supply and this allows for diffusion of nutrients into the IVD through the cartilage end plate.

The annulus fibrosus (AF) is a series of super strong well organized concentric lamellae of fibrocartilage that surround and protect the nucleus pulposus (NP) of the IVD

The NP is the innermost jelly like substance made up mainly of water and proteoglycans. The NP helps distribute pressure evenly across the IVD and prevent excessive forces loading the spine. This is what can herniate through the AF, causing what is commonly know as a 'slipped disc' or prolapsed intervertebral disc (PID).

A group of researchers performed a comprehensive *scoping review on peer-review publications on the blood supply of human IVD's excluding disc herniations. 22 out of 3122 articles found met the inclusion criteria of fetal to > 90 years old, various health status and both sexes using gross dissection, histology or medical imaging to assess if there is blood supply.

Consistent observations from this review were that there is no blood supply in the NP of the IVD throughout life. 

Both the cartilage endplates and AF have considerable blood supply during fetal development and in infants, but decreases over our lifespan. A common feature of the cartilage endplate was the presence of channels throughout the tissue, likely from the well vascularized vertebral endplate from the adjacent vertebrae. Between birth and ten years of age, there is a drastic decrease in blood vessels within these channels; which are not seen at all in adults.

However, there are blood vessels growing into the endplates and inner layers of the AF especially when there is damaged or disrupted tissue regardless of age. This is more common in older adults. Location of blood vessels are variable. 

It is thought that annular fissures or tears associated with degenerated discs are perhaps more conducive to the ingrowth of blood vessels since there is a loss of proteoglycans (a protein compound found in connective tissue) due to the healing process. Interestingly, there are also nerves found together with the blood vessels suggesting some patients may get more pain than others with such conditions.

Through this scoping review, we now know that the IVD is not entirely avascular as often thought and cited. This is great news for patients. We always knew that you can heal from a "slipped disc", but the discs having a blood supply means a better chance that it can heal from an injury.


Fournier DE, Kiser PK, Shoemaker JK et al (2020). Vascularization Of The Human Intervertebral Disc: A Scoping Review. JOR Spine. 15: 3(4): e1123. DOI: 10.1002/jsp2.1123.

*A scoping review has a broader scope compared to traditional systematic reviews with correspondingly more expansive inclusion criteria.

* you can read more about slipped discs and how slipped discs can heal here.

Sunday, July 11, 2021

Mouthwash Reduces Exercise Benefits

I brush my teeth at least 3 times a day, but usually do not use mouthwash. Actually I do, I grind my teeth at night and wear a night splint so as not to wear out the enamel in my teeth. Sometimes, I soak my splint in mouthwash to have that fresh minty sensation when I'm wearing it.

Do you use mouthwash? A study (Cutlet et al, 2019) found a surprising link between mouthwash and nitric oxide levels. Yes, using anti-bacteria mouthwash can affect your nitric oxide levels.

We know that exercise helps to lower your blood pressure (BP). When we exercise, the cells in our blood vessels and muscles produce nitric oxide. Nitric oxide helps widen our blood vessels and lowers our BP. This continues after exercise and our BP remains low. The bacteria in our mouth helps to recycle nitrates produced during exercise into nitric oxide. 

So if you use mouthwash to kill those helpful microscopic bugs, you are also spitting them down the drain and this can affect your blood pressure. This can also mess with your sporting performance.

Researchers from that study (Cutler et al, 2019) had a group of healthy man and women  run two 30-minute treadmill tests. After the first run, the runners rinsed their mouths with either an anti-bacterial (0.2 percent chlorhexidine) mouth wash or an inactive, mint flavored rinse.

After the second run, their mouth washes were switched. Neither the runners nor researchers knew which mouthwash the runners were rinsing with each time. BP and blood samples of the runners were taken before each session and two hours after the run.

When the mint-flavored placebo rinse was used, their systolic BP ( the highest BP level when the heart is squeezing and pushing oxygenated blood into circulation) was reduced by an average of 5.2 mm Hg one hour later. However, when the anti-bacteria mouthwash was used their BP fell by only 2mm Hg (> 60% less than the placebo) over the same time period.

What was worse was that the BP lowering effects completely disappeared  after two hours when using the anti-bacteria mouth wash. 

Moreover, their blood nitrate levels did not increase after the runners used the anti-bacteria mouthwash. However it spiked when they used the placebo rinse.

This shows that oral bacteria play a key role in the cardiovascular effects of exercise, specifically the vasodilation and lower BP after exercise. The nitrates formed during exercise are absorbed by the salivary glands and secreted in the mouth. Oral bacteria in the mouth then reduces it to nitrite in the recovery phase after exercise. Once the nitrite is swallowed, it can be absorbed into the bloodstream to form new nitric oxide to help sustain the blood supply to previously active tissues.

Since mouth wash lowers nitrite availability, this may impair cardiovascular response associated with exercise, although more research is needed to study this in greater detail.

Since we already know that runners and other endurance athletes  tend to have poorer dental health, it may not be wise to rinse your mouth with anti-bacteria mouth wash. Instead, eat less sugar and brush your teeth regularly to maintain good dental hygiene . Otherwise, you may not get the most out of the the vessel widening, circulation boosting benefits from exercising. This would be a real pity.


Cutler C, Kiernan M, Willis JR et al (2019). Post-exercise Hypotension And Skeletal Muscle Oxygenation Is Regulated By Nitrate-reducing Activity Of Oral Bacteria. Free Rad Biol Med. 143: 252-259. DOI: 10.1016/j.freeradbiomed.2019.07.035

Sunday, July 4, 2021

Forward Lunges To Strengthen Your Knees?

Lunges by our 3 physios

A patient came in complaining of knee pain after running. Since she also did strength training with a personal trainer, she was instructed to do forward lunges (FL) to strengthen the muscles "around the knees" to avoid knee pain. Yes, the lunge is a very popular strengthening and loading exercise that is often prescribed by many health professionals. 

Alas, the front lunges made her knee pain worse.

After examining her, I explained that her knee pain was more likely coming from her hip. Meaning, she feels the pain in her knees, but the cause of her problem is her hips.

In addition, FL exert a much greater load on the patellofemoral joint compared to backward lunges (BL). I recall just reading a published article where researchers studied a group of young healthy females comparing front and back lunges.

47 body markers were placed on different parts of their bodies to record data from two force platforms in addition to 15 motion analysis cameras. The female subjects performed 10 consecutive forward and backward lunges and the researchers analyzed the middle six. 

The researchers found that peak patellofemoral joint (PFJ) reaction forces were 18.1 percent higher in FL compared to BL during the upward phase. Peak PFJ stress was 9.55 percent higher in FL compared to BL.

Peak quadriceps (or thigh) force was 18.3 percent higher in FL.  Knee bending angles were 5.85 percent larger in the upward phase of FL compared to BL. Most importantly, average PFJ loading rate was 124 percent higher in FL compared to BL. 

These results suggest strongly that there is much higher PFJ loading in the FL compared to BL. Exactly why my patient's knee pain got worse after doing her lunges. 

So if you're having knee pain, it may be best to avoid doing forward lunges until it settles. It may also be wise to strengthen your calf muscles instead.


Goulette D, Griffin P, Schiller M et al (2021). Patellofemoral Joint Loading During The Forward And Backward Lunge. Phy Ther in Sport. 47: 178-184. DOI: 10.1016/j.ptsp.2020.12.001

Saturday, June 26, 2021

How Much Exercise Is Good For Your Brain?

I rode 105 km before work this morning. No prizes for guessing I was thirsty, hungry (despite eating before I started work) and needless to say, tired. 

There are days when after a run or ride I feel alive, my mind is laser clear, and all my synapses are firing. Today's ride was definitely not a ride where I felt clarity afterwards. 

There's plenty of evidence that short bouts of moderate exercise improves your performance in the ability to perceive, react, process and understand, store and retrieve information, or do cognitive tasks afterwards. You may not feel it, but the finding is highly repeatable.

However, we do not know how much exercise is enough to trigger this effect. Or whether how fit you are or what type of cognitive task you're doing matters.

I found an article where researchers in Australia tested 21 trained cyclists and triathletes (11 male, 10 female). These athletes did 15 minutes of moderate cycling followed by a pair of cognitive tests lasting 4 minutes. They rode another 30 minutes moderately before repeating the same cognitive tests. This was followed by an incremental ride to exhaustion (taking about 11 to 12 minutes on average) before doing a final round of cognitive tests (McCartney et al, 2021). Three different timepoints were measured, after 15 minutes, 45 minutes and exhaustion.

Moderate cycling was done at 50 to 55 percent of peak power from a previous test and this got them to average 75 percent of max heart rate (HR) after 15 minutes and 80 percent of max HR after 45 minutes.

Results showed that 45 minutes of exercise trumped 15 minutes. For these trained endurance subjects, their cognitive performance decline definitely did not happen after 45 minutes of moderate exercise.

Contrary to what the researchers expected, the decline did not happen after complete exhaustion as well, being better than after 15 minutes. Note that there was a 2 minute delay from the moment of exhaustion until the start of the cognitive tests so this delay may just be enough to recover.

Bear in mind that exercising for longer does not always mean better since there will be a point for everyone where if you exercise long enough your cognitive performance will start to drop. 

These subjects were also not allowed to drink during the testing. Male subjects lost 2.3 percent of their starting weight while the females lost 1.7 percent. This is well above the threshold suggested to cause cognitive impairment. 

The subjects repeated the testing twice. In one testing, they were given 2 capsules and told that the capsules were "designed to enhance cognitive function" during exercise. 

The capsules were just placebos, as the researchers wanted to test whether the subjects were influenced by this. The placebos did not have any significant effect which supports the case that this is a physiological effect - a result of enhanced blood flow to the brain or elevated levels of neurotransmitters.

There was another study done in 2015 where researchers from Taiwan found that 20 minutes of moderate exercise produced the biggest cognitive boost, compared to 45 minutes. The biggest difference between the two studies is that this Taiwanese study used healthy but non athletic university students (Chang et al, 2015).

Since the 2021 study used trained endurance athletes, it makes sense that they will probably benefit from a longer exercise duration compared to the university students.

There you have it, exercise does makes you improve your brain function. However, we cannot always go out for a run or ride before an important meeting, deadline or decision. It can also be shooting hoops or lifting some weights or any other exercise if running or cycling ain't your thing. Just do it when you have the opportunity.


Chang YK, Chu CH, Wang CC et al (2015). Dose-Response Relation Between Exercise Duration And Cognition. Med Sci Sp Ex. 47(1): 159-165. DOI: 10.1249/MSS.0000000000000383

McCartney D, Desbrow B and Irwin C (2021). Cognitive Effects Of Acute Aerobic Exercise: Exploring The Influence Of Exercise Duration, Exhaustion, Task Complexity And Expectancies In Endurance-Trained Individuals. J Sp Sci. 29(2): 183-191. DOI: 10.1080/02640414.2020.1809976.

Our Sat ride before Covid-19

Sunday, June 20, 2021

Are S&C Coaches Or Physiotherapists The Real Exercise Professionals?

This week's post is on an article I read in the blog from the British Journal of Sports Medicine where the author asked whether physiotherapists or strength and conditioning (S&C) coaches are the real pros when it comes to prescribing rehabilitation exercises and getting patients/ athletes to return to sport (RTS).

The author compared physiotherapists and strength and conditioning (S&C) coaches working with athletic populations (in the UK). His view was that the physiotherapist has always been the decision maker or 'top dog' when it comes to managing the injured athlete or any patient that needed exercise to rehabilitate or improve physical function. 

He feels that the physiotherapy profession has not kept up to date with professional developments in exercise science and S&C, even falling behind and out of step in some aspects. This is despite the fact that there has been an increase in demand by physiotherapists in the UK for weekend courses in S&C training to fill in gaps in expertise and knowledge. 

The author thinks these short 2 day courses is "really an insult to those S&C professionals that have devoted time, effort and financial resources to their expertise" as they have studied exercise science, S&C at undergraduate level and gone on to postgraduate study and even advanced professional accreditation to work.

He also feels that the undergraduate training program for physiotherapists in the UK does not provide enough basic grounding in exercise prescription and training science despite claims by the physiotherapy profession that they have a firm grounding in basic clinical sciences so they can circumvent the need for extensive training in S&C.

This has then led to a deficit in rehabilitating athletic populations such that it even slows an athlete's full RTS. The athlete is usually handed to the S&C team or left to their own devices. He concludes that rehabilitation of recreational and professional athletes must be recognized as an advanced practiced skill requiring specialist training. If these gaps/ deficits in both under and post graduate training are not addressed, then physiotherapists will be relegated to technicians in the restoration of the patient/ athlete.

My thoughts? I used to work at the *Singapore Sports Council in the Sports Medicine department (the current Singapore Institute of Sport). The doctors, physiotherapists, S&C coaches and other sports science staff (nutrition, biomechanics, psychology) all have degrees and/ or postgraduate qualifications and definitely had a good working relationship. We had a weekly case discussion where the athletes who were not progressing well after injury were brought up and analyzed.

Other than that sort of setting and perhaps in the Singapore Sports School and Football Association of Singapore, I think that physiotherapists in  hospitals and private practices that treat sporting populations may differ in their ability to enable these patients to RTS. It boils down to the interest and exposure of each physiotherapist. Whether they had any previous sports/ athletic background, how interested they are in sports, and most importantly, their tenacity to want to better themselves. 

There will be S&C coaches, sports and functional trainers, CrossFit coaches and personal trainers who, with their interests and commitment to improve themselves, will be superior to some physiotherapists with regard to rehabilitation and returning patients to sport. Likewise, there will be physiotherapists who can more than hold their own. 

It is, ultimately, up to each individual in their respective line of work to keep themselves up to date, to keep improving to help athletes recover better and faster. And also to recognize when they aren't the best person to return an athlete to sport and refer them out to someone who is.


Blog article from British Journal of Sports Medicine, published on May 2, 2021.

* Thanks to my former colleagues and former S&C coaches Todd Vladich and James Wong (also multiple SEA Games gold medalist and discus throw record holder), whom guided my S&C program when I was still competing. James, a few other colleagues and I used to train at the old KATC gym at the old National Stadium 3 mornings a week at 7:30 am before we started work when we were not traveling or competing. We did this year round, especially in the off season. Those sessions and attending a Level 1 Australian Weightlifting Federation course while working there definitely made me competent at getting patients to return to sport quickly and most importantly, safely.

Sunday, June 13, 2021

Evidence For Using Floss Bands

showing Byron, Thiviyan and Megan
Remember the floss band courses we used to teach? We often had participants asking what is the evidence behind increasing joint range of motion (ROM), sporting performances, helping with recovery and decreasing pain. In short, they all wanted to know how it works

I wrote previously that you've got to try it to believe it, well there is now a published *scoping review article for floss bands (Konrad et al, 2021), referenced below.

The review paper summarizes the existing evidence for the effect of floss band treatment on range of motion (ROM), sporting performance (strength or jump performance), recovery (due to DOMS) and pain (due to disease or injuries).

In all, 24 studies met the inclusion criteria with a total of 513 subjects. 15 of the 24 studies investigated the effects of a single floss band application on the ROM of several joints. On the ankle joint, flossing was found to have a significant change of 11.17% in the dorsiflexion ROM.  

4 studies investigated the effects of calf flossing on the ankle, showing a very large increase of 19.95% in dorsiflexion of the ankle.

Similarly 4 studies measured thigh flossing and found a significant increase in knee bending (3.61%), and knee straightening (7.38%). However, another study showed no improvement in hip ROM after flossing the thigh. None of studies showed any decrease in range after flossing.

Of the two studies that investigated the effects of flossing on DOMS, one study reported significantly reduced DOMS 24 and 48 hours post exercise in the study group (in the upper arms) compared to the control group. The other study (on leg muscles) found no difference in the intervention versus control group following 12, 24, 36, 48 60 and 72 hours post exercise.

When comparing flossing to other treatment like dynamic stretching, flossing had a more noticeable effect in increasing hip range of motion and maximal eccentric knee extension (Kaneda et al, 2020b). With regards to static stretching and flossing, rate of force development was more pronounced in the flossing group compared to the static stretching group (Kaneda et al 2020a). Kaneda and colleagues concluded in both studies that flossing should be applied as a warm up rather than as a stretching exercise. This is exactly what my patients who do CrossFit tell me. They normally use a floss band for warm up before they start their easier routines, before the heavy lifting.

I know all athletes are after improved performances. Results from the individual studies showed that 11 of of the 44 performance measures showed a significant improvement (comparing pre and post floss band application, Table 3 in article). There is some evidence that joint flossing (ankle and knee) can increase jump height, although sprint performance (5 to 20 m sprints) seems to be unaffected after ankle flossing. (Personally, I would floss the quads and hamstrings and calf muscles if I wanted to improve sprint times rather than the ankle). 

One study showed improvement in maximal voluntary contraction (strength) in the quadriceps muscle and hamstrings after thigh flossing.

The researchers suggest this is possibly due to hormonal responses related to the flossing. Similar to other occlusion (or blood flow restriction methods), enhanced growth hormone and norepinephrine levels increase may be responsible for increase in performance reported. More importantly, the review concluded that from the involved studies there was no detrimental effects on performance from a single floss band treatment.

Evidence also show that a single floss band treatment is able to increase ROM of the related joint and can positively affect jumping and strength performance. Possible mechanism is suggested to be changed neuromuscular function rather than changed mechanical properties.

after surgery in 2016
After Ronald Susilo (above) ruptured his patella tendon and tore his anterior cruciate ligament at the same time, he came to see me after the surgeon reattached his patella tendon. He did not have the range to even pedal one round on the stationary bike. I definitely increased his knee ROM with a single floss band treatment. He could pedal immediately after a single floss band application. 

Yes, back then it was only one subject (or n=1), however it was a definite improvement. Those of you reading then may be critical and probably not even believe it, but I have since replicated it many times in our clinic. Hence I feel that clinical evidence (what we see in the clinic) is just as good as published evidence (like this scoping review).

There will probably be long term studies about the effects of flossing treatment on joint ROM, sporting performance, whether it helps with recovery and decreasing pain. I am sure there also will be studies that say there are no benefits to it. The question is does it work for you?


Konrad A, Mocnik R and Nakamura M (2021). Effects Of Tissue Flossing On The Healthy And Impaired Musculoskeletal System: A Scoping Review. Front. Physiol. 21 May 2021. DOI: 10.3389/fphys.2021.666129

*A scoping review has a broader scope compared to traditional systematic reviews with correspondingly more expansive inclusion criteria.

Let's do the twist