Sunday, March 28, 2021

Overdoing HIIT Sessions Can Affect Your Health

Picture by Ving Henson from The Pit

Many of my patients tell me they are doing HIIT classes now. If you interested about your fitness and have been exercising regularly, you will definitely know what HIIT stands for. High intensity, interval training.

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).

I've written how HIIT can be beneficial and how it can even reduce growth in cancer cells. Since HIIT is a super time efficient method for improving aerobic fitness and other health outcomes and metabolic conditions such as diabetes, high cholesterol or high blood pressure.

One such outcome is increasing our cell mitochondria (power generators in our cells) in our muscles. With more mitochondria in our cells, we become stronger. 

Before you think more HIIT is better, a recent small study showed that people who tried to do 5 HIIT sessions in a week ended up with sudden and severe declines in their mitochondria function, along with blood sugar dysfunction. 

When the subjects decreased their HIIT sessions, their metabolic condition started to improve but did not disappear, hinting that the benefits of extremely strenuous exercise may still depend on how much we do and how we allow ourselves to rest and recover.

The researchers first tested the subjects in their lab for the current fitness levels and metabolic health, which included blood sugar levels throughout the day. In the first week, 2 sessions of HIIT were performed, 5 reps of 4 minute long bike intervals on a stationary bike with 3 mins rest in between. The subjects pedaled as hard as they could while their power output was tracked. Their leg muscles were biopsied while a 24 hour blood sugar control was investigated.

In week 2, they did 3 HIIT sessions while increasing some of their intervals to 8 minutes. During week 3, they did 5 HIIT sessions with a mix of 4 and 8 minute intervals of all out cycling. Week 4 allowed for some recovery and they subjects and the amount and intensity of exercises were halved. All the tests were repeated weekly.

The findings showed the subjects getting stronger by week 2. They were pedaling harder and getting fitter, better daily blood sugar control and more mitochondria in the cells. These mitochondria were also more efficient, producing greater energy compared to baseline.

However, by week 3, the subjects were not able to generate more power, their muscle biopsies showed that their mitochondria were only producing 60 percent of the energy of week 2. Blood sugar control levels were spiking and dipping throughout the day.

After allowing for recovery in week 4, the following week showed the mitochondria producing more energy, but still 25 percent less than week 2. Blood sugar levels stabilized too, but again not to the same extent as week 2. The subjects could however ride with the same or even greater vigor as with week 2.

The researchers did not find out what exactly caused the decline in results (glucose intolerance and insulin secretion)  that occurred after week 3. It may be the combination of total biochemical changes that weakened the mitochondria which in turn disrupted the blood sugar control levels. 

This study was done on normal healthy subjects and not athletes nor people with metabolic conditions such as diabetes, high cholesterol or high blood pressure. The latter group attempting such training must get the go ahead from your medical professional. For those of us who just want to be healthier, don't do HIIT sessions excessively since previous studies and formal recommendations suggest 3 intense sessions in a week as maximum. Otherwise, injuries may come knocking on your doors too. 

The researchers managed to assess blood glucose profiles in world class endurance athletes and found that they, too had impaired glucose control when compared with a matched control group. So for athletes who want to be stronger, faster quicker, do allow ample time for recovery between training sessions.


Flockhart M, Nilsson LC, Tais S et al (2021). Excessive Exercise Training Causes Mitochondrial Functional Impairment And Decreases Glucose Tolerance In Healthy Volunteers. Cell Metab. DOI: 10.1016/jcmet.2021.02.017

Sunday, March 21, 2021

Reliable Predictors Of Running Injuries

You need a new pair of running shoes so you decide to go to a specialist running store to choose a pair that's suitable for you. The store manager at the specialist running store tells you to hop onto their in store treadmill and 'analyzes' your running gait.

He then proceeds to critique your running gait and its biomechanical implications. And suggests the most expensive running shoe (in the store) for you so you do not get injured. Is that a common scenario that happens?

Contrary to several long held beliefs, most biomechanical and structural factors are not reliable factors at predicting running injuries

Researchers studied 300 runners who have been injury-free for the past six months and found several more reliable factors (rather than biomechanical and structural factors) in predicting who would be more likely to get injured.

The runners' demographics, physiology, biomechanics, psychosocial issues and training were documented. Their hamstrings, quadriceps muscle strength, knee, ankle flexibility, arch height of their feet were tested. 

A gait analysis studied how their feet, knees and hips distribute forces while running

Any runner who reported an injury were followed up at six and twelve months later. After the first year, the researchers emailed the injured runners a biweekly questionnaire asking them what injuries they sustained in the past two weeks.

Those that were injured went to a doctor and physiotherapist who were part of the study for treatment.

Results of their study after the two year follow up indicate that female runners sustain injuries at a higher rate than male runners. Stiffness in the knee joint, which were more common in runners weighing more than 80 kg significantly increases the chances of an overuse running injury. 

The runners who were injured also reported significantly worse mental health related to their quality of life and more negative emotions compared to the non injured runners.

Most biomechanical, structural factors like arch height, overpronation, flexibility, Q-angle  (see picture above), lower limb strength, weekly mileage, footwear and previous injury are not reliable factors for overuse running injuries.

The researchers recommended that caution should be used when trying to alter what were commonly thought risk factors such as excessive pronation, poor flexibility, weekly mileage etc unless a runner has extreme values.

It appears from this study that the importance of biomechanics and anatomical structures assumed by doctors, physiotherapists, personal trainers and other clinicians are not as high risk as assumed. 

I feel that this does not mean they are not important. It is still important to consider the individual patient/ runner when assessing their condition. 

We still need to be aware of each patient's individual structural and biomechanical anomalies, but not to the point where we nitpick every discrepancy in strength, joint angle, foot position and range of motion.      


Messier SP, Martin DF, Shannon L et al (2018). A 2-Year Prospective Cohort Study Of Overuse Running Injuries: The Runners Injury Longitudinal Study (TRAILS). AJSM. 46(9): 2211-2221. DOI: 10.1177/0363546518773755

Sunday, March 14, 2021

Is It Better To Bend Your Back Or Knees When Picking Something Off The Ground?

Thanks to Tasneem and Joakim for the photo
I can't find any similar statistics in the local Singapore context, but more than 40% of employees in European countries suffer from work related musculoskeletal disorders (WMSD) yearly. This results in 3-6% absence from work, affecting 2.5% of the gross domestic product across Europe. 52% of injuries are attributed to overloading during lifting tasks, of which 65% affect the lower back.

When picking up something off the floor, we generally use two standard lifting techniques, the stoop or squat technique, which have been well described in many articles. The squatting technique is usually advised when lifting heavy objects since this technique is thought to result in lowering intervertebral disc (IVD) compression and shear forces compared to the stoop technique. 

Squat (a) versus Stoop (b)
Stoop lifting is usually restricted to lifting light objects since it is thought that stoop lifting causes higher IVD compression and shear forces compared to the squat.

However, there is no agreement or sound evidence for lifting ergonomic guidelines (or good lifting techniques). Hence the following study to investigate if squat or stoop lifting imposes more load on the person lifting.

Different weights were tested for both lifting techniques using a full body musculoskeletal model, 3D marker and ground reaction forces. They were used to calculate joint angles, forces and power. Muscle activity of nine different muscles were also measured to calculate effort.

Ready for the results? For all lifting conditions and both techniques, the highest joint forces during lifting and lowering were at the L5S1 spine levels, followed by the hip and knee. The hip joint generated the most power while lifting for both techniques.

Squat lifting was mainly executed by additional work on the knee extensors (Quadriceps), shoulder and elbow, potentially explaining similar prevalence of WMSD in the shoulder, elbow to LBP in people who do frequent lifting. 

The authors concluded that based on their findings, squat lifting is not favored over stoop lifting (this is in contrast to current recommendations) although forces were slightly higher in the L5,S1, hip and knee during the stoop technique. This is also supported by Van Dieen et al (1999) who concluded that there is no evidence to suggest squat over stoop lifting after reviewing 27 studies.

Now, many of you reading this may already not agree with what the authors concluded. There are so many variables that can change the results. How low the object is will influence the load on the back, making comparisons with other studies difficult. 

Even a small adjustment like turning the knees out (not controlled in this study) while squatting already reduces back loading. Likewise, healthy volunteers in this study will likely have different lifting dynamics compared to real blue collar/ laborers since the latter would have efficient strategies for all the lifting done over the years. Lifting in the research setting may not totally replicate real world situations.

Weight (10kg in this study) and dimensions of the load lifted will definitely affect the lifting technique as well since the box (length 36 cm, width 14 cm and height 21 cm) used in this study was relatively small. 

For those of you who do not have low back pain, this post may possibly challenge or even change the way you lift a box off the ground or while picking a pen that you've dropped. You have always been told that when you're picking up something or lifting that you should bend your knees, keep your back straight before you lift. That is supposed to be good form or good ergonomics.

Well, especially for those of you who are pain free, you can say to anyone who insist you bend your knees and not your back while lifting that it is not totally true. 


Van Der Have A, Van Rossom S and Jonkers I (2019). Squat Lifting Imposes Higher Peak Joint And Muscle Loading Compared to Stoop Lifting. Ap Sci 9(18): 3794. DOI: 10.3390/app9183794

Van Dieen JH, Hoozemans MJM and Toussaint HM (1999). Stoop Or Squat: A Review Of Biomechanical Studies On Lifting Technique. Clin Biomech. 14: 686-696

Thank you for reading this long article. If you're interested, another study by Mawston et al, (2021) pictured above and referenced below found that during a maximal lift in pain free individuals, a flexed lumbar spine (picture C) is more efficient and stronger as opposed to a straight spine! So much for having a 'good' posture while weight training. Perhaps that shall be another post.

Mawston G, Holder L, O' Sullivan P et al (2021). Flexed Lumbar Spine Postures Are Associated With Greater Strength And Efficiency Than Lordotic Postures During A Maximal Lift In Pain-free Individuals. Gait and Posture. DOI: 10.1016/j.gaitpost.2021.02.029

Sunday, March 7, 2021

No Need To Stretch Or Foam Roll Your ITB?

You are a runner and you haven't been able to run more than 2 km before a sharp pain in your outer knee reduces your run to a hobble. Resting, icing and changing your running shoes made no difference. The sports doctor you saw just diagnosed you with the dreaded Iliotibial Band Syndrome (ITBS). He tells you that you need to stretch your Iliotibial band (ITB) and use a foam roller.

Sounds familiar? Well, this latest published paper on the ITB by Paul Giesler (2020) challenges common treatment approaches of stretching and massaging the ITB. Basically, he says that you do not want to stretch or foam roll your ITB.

I've written about the ITB before in a few different posts. Except for Daniel Liberman and Carolyn Eng's study, most other articles seem to suggest that the ITB causes pain via a 'friction syndrome'. This is thought to be due to the ITB rubbing to and fro over Gerdy's tubercle on the outer shin bone while running due to hip weakness. 

Treatment is normally targeted at stretching the ITB (to reduce friction). Doctors will often suggest a steroid injection to reduce 'inflammation' (in the bursa) on the outer knee.  Giesler (2020) however,  suggested that ITB pathology is more likely to involve compression of sensitive structures beneath the ITB rather than friction.

also know as Iliotibial tract (ITT)
Since the ITB is a really broad, strong and complex structure with many attachments (picture above) along the hip, thigh and around the knee, it can provide stability for both the hip and knee. Like I wrote before, the ITB is actually thought to function like our Achilles tendon. To store and release energy like a spring. Therefore you cannot and would not want to stretch a spring. A coiled spring can release energy much better than a spring that is stretched out.

From Carolyn Eng's running simulation 
Hence the need to treat the cause of the problem rather than just treating the pain over the outer knee. Hip strength and control thus thought to be key in causing ITBS, especially weakness in hip increased hip adduction (dropping of the hip inwards) during loading. 

Runner on L has increased hip adduction
In runners/ patients with excessive hip adduction while running, progressive rehab and addressing potential causes should be adapted for individual runners, especially while running downhill and during longer runs. I've written on this topic specifically, you can read that article here.

So treatment should be to calm the symptoms (knee pain) and treat the cause. We don't get you to stretch your ITB or use the foam roller in our clinics, come see us if you want to run pain free.

The Paul Geisler (2020) article is free, click on the link under references if you want to read it.


Bramah C, Preece SJ Nimh G et al (2018). Is There A Pathological Gait Associated With Common Soft Tissue Running Injuries? AJSM. 46(12): 3023-3031. DOI: 10.1177/0363546518793657

Eng CM, Arnold AS, Liberman DE et al (2015). The Capacity Of The Human Iliotibal Band To Store Elastic Energy During Running. J Biomech. pii: S0021-9290 (15) 00354-1. DOI:10.1016/j.jbiomech.2015.06.017.

Geisler PR (2020). Iliotibial Band Pathology: Synthesizing The Available Evidence For Clinical Progress. J Ath Trg. DOI: 10.4085/JAT0548-19