Sunday, October 25, 2015

Maybe You Didn't Exercise Hard Enough?

Picture by Irving Henson from The Pit
I've got some friends who really love eating and some of them have been complaining to me that exercise just doesn't seem to work for them. Despite exercising regularly they seem to be packing on the pounds still.

Maybe you didn't exercise hard enough? That was the first thing that came to mind when they asked for my thoughts on that matter. Granted, I know not everyone responds the same way to a certain exercise program. Turns out I may be right when I recently came across the following article.

Researchers studied 121 sedentary and obese adults who exercised five times a week over a duration of 24 weeks.

The subjects were split into three groups. A low intensity, low duration group who did moderate walking (31.2 minutes of exercise at 50 percent VO2 max). The second group exercised at low intensity but longer duration (57.9 minutes of exercise at 50 percent VO2 max). The final group did a higher intensity, longer duration of brisk walking (39.7 minutes at 75 percent VO2 max).

After four weeks there were "non-responders" across all three groups. Non responders were those whose fitness levels did not improve.

The number of "non-responders" decreased as the weeks passed although they remained in the low intensity groups. There was however, no "non'-responders" in the high intensity group, meaning everyone in that group got fitter.

The researchers suggested that there will not be any "non-responders" as long as they exercised hard enough for long enough.

Hard enough in this study basically involved brisk walking, meaning you may need to do more if you're younger and fitter.


Ross R, de Lannoy L and Stotz PJ (2015). Separate Effects Of Intensity And Amount Of Exercise On Interindividual Cardiorespiratory Fitness Response. Mayo Clinic Proceedings. pii: S0025-6196(15)00640-0. DOI: 10.1016/j.mayocp.2015.07.024.

Walk this way! (Picture by Irving Henson from The Pit

Friday, October 16, 2015

What About Energy Return In Your Running Shoes?

How many of you recognize this shoe? Reebok ERS 5000- from 1988
Runners, don't you want running shoes that not only protect your feet but give you energy as you go?
It seems that many shoe companies are joining the energy return movement again. Why did I say again?

Well, looking at the picture above, how many of you will know what I'm talking about if I mention "ERS"? To be specific, the Reebok ERS or energy return system technology Reebok came up with in 1988 to compete with the Nike Air technology. That was way back in 1988!

Let me sidetrack a little. The ERS comprises of a series of cylinders made from Dupont Hytrel placed in the midsole of the shoe to act as springs. This was meant to help propel the runner forward after foot strike or so Reebok claims. (Note - ERS was phased out when Reebok invented Hexalite their next technology). Come talk to me if you wanna discuss shoe technology from the 80's and 90's.
The Adidas Boost
In the present day, there's Adidas claiming its Boost midsole material will "keep every step charged with an endless supply of light, fast energy." Puma's IGNITE foam says "Energy in. More energy out." Saucony tells you its new Everun foam will give you "increased energy return" and a "lively underfoot sensation."

When a running shoe cushions well, it also lowers the responsive response of that shoe (since it has to absorb the force). A responsive shoe means firmness in that shoe and that firmness allows you to transfer the force from your stride into running faster.

And cushioning and responsiveness are mutually exclusive. Either you have a shoe that is soft and cushions your landing by dissipating that energy or a shoe that allows your to put your energy directly into propulsion.

These new energy return shoes try to combine the two properties. They absorb more than the previous traditional foam used in running shoes and then store that energy that was absorbed to return the foam to original shape quickly producing a responsive feel as they push back on the bottom of your foot during push off.

Despite what the ads say, no material can actually produce energy that can propel your next running step. No foam can actually do that. The basic law of physics states that no system creates or destroys energy. Energy can only be transformed. If anything, what energy that is returned tends to be generated by your own stride in the first place.

Even if the foam did bounce back harder than it was compressed, it is unlikely it can propel you in any meaningful way. This is because running involves forces generated by your muscles, joints, tendons and bones along with gravity and friction. In order to get that "energy return", the energy has to be returned at the right time, frequency and right location (Nigg, 2010). It just doesn't happen so easily.

The running shoe industry has yet to get all these variables working together, regardless whether the rebound is from foam, tubes, springs or mechanical trampolines used by Newton, Spira or any other brand currently.

Moreover, the current energy return foam is fairly heavy. Weight has a large impact on running shoes. Previous studies show that for every 100 grams (or 3.5 ounces) added to your foot, energy cost is increased by one percent. This is also why you want to use racing flats when you race as a lighter shoe allows your foot to turnover faster and thus leading to faster race times.

If you have tried some of these newer "energy return" shoes though, you just might be sold on them. They actually feel fantastic when you first try them on. One of my patients who's tried it said his feet felt like a million dollars. But like I always say, it's the legs (and running technique) that makes you fast not the shoes.

Previous studies have shown that your own muscles and tendons and a good running technique will reduce overall impact forces better than the midsole of your running shoe can. What is important in the cushioning of the shoe is spreading the load across your foot. This may explain why those who switched to minimalist/ barefoot running type shoes had no more knee or hip pain but ended up with stress fractures on their metatarsals (or foot bones) instead. This of course lead to a huge outcry against such minimalist/ barefoot running type shoes.

So, now you know that getting energy return or propulsion is not so straight forward and not something you should expect from a shoe. Not yet anyway.


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

Nigg BM (2010). Biomechanics Of Sports Shoes. Calgary, Alta. : University of Calgary, c2010.

Sunday, October 11, 2015

How To Prevent Age Related Running Speed Loss

Now that's a strong calf
It's a sad fact but true. As a runner, you get slower as you age. This is partly due to the weakening of muscles around your ankles and calves according to a recently published article.

The article looked at a whole range of variables across a wide range of runners. The runners studied ranged from age 23 to 59 years old. The runners were filmed running at their normal pace on a treadmill with a high speed video camera.

The older runners in the study maintained the same stride frequency as the younger runners (about 83 strides/ minute). The one glaring difference was that they had a much shorter stride length, which the authors felt reduced their running speed.

Stride length and running speed decreased by about 20 percent from age 20 to 59. Ankle power also dropped by almost 48 percent during the same time frame leading the researchers to conclude that runners could probably maintain their running speed by increasing their calf muscle strength and power.

The authors suggested that strengthening the gastrocnemius and soleus muscles (which make up the calf muscles) will benefit runners. They suggested using a combination of slow reps but with heavy weight workouts and faster but using lower weight power workouts to strengthen the calf and to stave off the slowdown.

The authors were also impressed that the runners managed to maintain their weight through the decades and suggested that long term running could be an effective way to maintain weight without medication.

Personally, I feel that if you ran with good technique, you won't need to strengthen your calves. Look at the Kenyans and the Ethiopians that win all the big races all over the world, have they got big strong calves?


DeVita P, Fellin RE et al (2015). The Relationships Between Age And Running Biomechanics. Med Sci Sports Ex. Epub. DOI: 10.1249/MSS.0000000000000744.

Here's another look - thanks to Vinny for the pictures

Friday, October 2, 2015

Don't Try Anything New On Race Day

Elid Kipchorge and his shoes
I was away on holiday this past week after teaching the Kinesio Taping Level 1-2 course over the week end and did not have regular internet access at where I was.

Having just returned, am catching up on all my mail and news and I came across the results from the recently concluded 2015 Berlin marathon.

Eliud Kipchorge ran and won in a personal best time of 2:04:01 hours in a pair of prototype shoes that malfunctioned!!

According to reports, Kipchorge started having problems with his prototype Nike Air Streak 6 barely just a kilometre into the race. He bravely ran on even after the insoles popped out at the 20 kilometre mark forcing him to run the remaining 22 kilometres with flapping insoles.

Look in your own running shoes and you will find a insole (or sock liner) which is usually easily removed and can be replaced by your own custom orthotic if needed.  They are normally fairly secure and I've never seen them come off during a run (or a race for that matter). Racing flats usually have flatter and thinner inserts that are often glued down and not easily removed.

He ended up with blisters on his left foot and a cut on his big toe with lots of blood.

Remembering he was a sponsored athlete, he added with good PR skills "We have talked with technicians and even the highest authority of the (Nike) company. They are resourceful people. Remember, in life, challenges must be present and I urge my fans to run to Nike stores and grab this version immediately when it's out".

Ethiopian running legend Haile Gebrselassie joked tongue-in-cheek that Nike shoes would never be better than his preferred brand of Adidas. Maybe that's why Gabrselassie joked about it, as Kipchorge was previously sponsored by Adidas.

As you've often heard from me, don't try anything new on race day. I've learnt the hard way before too. Now that's a different post.

Talking about the Nike Air Streaks, I owned a pair of the first version way back in 1997. You can see it below.
The original Air Streak