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