Author: skikinetics

Inventor of a science and associated technologies that leverage human performance in specialized activities such as skiing, skating and cycling. Nominated in 1995 for the Gold Medal in the categories of Applied Science & Engineering in the British Columbia Science Awards for discovering and articulating the process and the conditions under which the human lower limbs and balance system can negotiate a balance solution through the stack of equipment that resides between the sole of the foot of a skier and the snow surface.

WHY TRYING TO COPY HIRSCHER AND SHIFFRIN’S MOVES DOESN’T WORK – PART 2

In previous posts I discussed the two studies (1, 2) done by the University of Ottawa in 1998 that analyzed pressure under the feet of elite alpine ski instructors

The pressure data from the study that used 6 elite alpine ski instructors found maximal (peak) force ranged from a high of 1454 Newtons to a low of 522 Newtons. The graph below compares the peak force seen in pressure data captured from the 4 competitive skaters in their own skates from my last post to the highest and lowest peak force seen in pressure data captured from the 6 elite alpine ski instructors used in the 1998 University of Ottawa study.

In consideration of the fact that the researchers commented that force-time histories revealed that forces of up to 3 times body weight can be attained during high performance recreational skiing it is interesting that the peak force of one of the 6 elite alpine ski instructors in the study was less than the lowest peak force of one of the 4 competitive skaters in the 2012 University of Ottawa study while the highest peak force of one of the 6 elite alpine ski instructors in the 1998 study was almost twice the highest peak force of one of the 4 competitive skaters in the 2012 University of Ottawa study.

A significant challenge in attempting to conduct foot pressure studies with alpine skiers is the variability of the slope and environmental and piste conditions. Test conditions and variables, especially ice, can be tightly controlled in the conditioned environment of an indoor skating rink.

Although the studies did not provide pressure data that compared peak and average pressures for different ski instructors, the peak forces from one study reached up to 30 newtons per square centimetre.

In the spring of 2012 I was asked to modify a number of pairs of the same brand and model of a hockey skate for use in a study that would compare metrics derived from pressure data captured from a competitive skater’s own skates to the same metrics from data acquired  from skates I had modified. I saw this as an opportunity to document the effect of modifications made to hockey skates based on the principles of neurobiomechanics described in my patents and this blog. When I speculated that the metrics derived from the pressure data might show improvements as high as 10% (i.e. 110%) I was told that the study was unlikely to result in more than a single digit improvement of approximately 2% or 3%.

I modified the pairs of skates in the shop in the garage of my home near Vancouver. The modifications were general in nature and made without the benefit of data on the feet of the test subjects. No modifications were made after I shipped the hockey skates to the University of Ottawa. I was not involved in the design of the study protocol or the actual study. I was hopeful that the study would produce meaningful results because it would have implications that could be extrapolated to alpine skiing.

The graph below shows the highest peak force in Newtons recorded for each of the 4 competitive skaters in their own hockey skates (blue = OS) and in the hockey skates that I modified (red = NS). The improvement was immediate with little or no run in period in which to adapt. The percentage improvement for each skater is shown at the top of each bar.

The mean (i.e. average) improvement was approximately 190%. The only factor that improvements of this magnitude could be attributed to is improved dynamic stability resulting from an improved functional environment in the skate for the foot and leg of the user.

……. to be continued in Part 3.


  1.  ANALYSIS OF THE DISTRIBUTION OF PRESSURES UNDER THE FEET OF ELITE ALPINE SKI INSTRUCTORS – Dany Lafontaine, M.Sc.1,2,3, Mario Lamontagne, Ph.D., Daniel Dupuis, M.Sc.1,2, Binta Diallo, B.Sc.: Faculty of Health Sciences1, School of Human Kinetics, Department of Cellular and Molecular Medicine, Anatomy program, University of Ottawa, Ottawa, Ontario, Canada.
  2. ANALYSIS OF THE DISTRIBUTION OF PRESSURE UNDER THE FEET OF ELITE ALPINE SKI INSTRUCTORS – Dany Lafontaine, Mario Lamontagne, Daniel Dupuis, Binta Diallo, University of Ottawa, Ottawa, Ontario, Canada

WHY TRYING TO COPY HIRSCHER AND SHIFFRIN’S MOVES DOESN’T WORK

There appears to be a widely held perception within the ski industry, even among coaches and trainers at the World Cup level, that skiing like Hirscher and Shiffrin is simply a matter of observing and then copying their movements. There also appears to be a widely held perception that strength training and training on BOSU balls, wobble boards, slack lines and thick foam pads will transfer to improved balance on skis.

In a recent article, Nailing the Coffin Shut on Instability Training Ideas (1.), trainer, Bob Alejo, cites 59 papers on the topic of instability training in support of his position that not only are the assumptions about instability training improving balance in a specific activity incorrect, instability training may actually have a negative effect on performance.

As far back as 1980, I had found that an immediate improvement in skier performance after ski boot modifications was a reliable indicator that the modifications were positive. Sometimes this was evident in the first few turns. I had also found that equipment modifications or equipment changes that had a negative effect did not become obvious right away. I didn’t understand the reason for the immediate and sometimes dramatic improvement in skier performance following ski boot modifications. But I suspected it had something to do with improved skier balance.

By 1990, I had hypothesized that elite skiers are able to create a dynamically stable foundation under their outside ski and foot in a turn to balance on by rotating the edged ski against resistance from the sidecut and that this has the effect of extending ground reaction force from the snow out under the body of the ski. But even after the Birdcage studies of 1991 validated my theory, I still didn’t fully understand the reason for the dramatic improvement in skier performance in the Birdcage tests or following modifications made to conventional ski boots. Strain gauges fit to the Birdcage showed forces and the sequence of loading. But the strain gauges could not measure the magnitude of the forces.

It was Dr Emily Splichal’s (2.) that answered my question when she said;

It doesn’t matter how physically strong you are. Without a foundation of stability, you are weak. With a foundation of stability, you are stronger and faster than anyone.

In his article, Nailing the Coffin Shut on Instability Training Ideas (1.), Alejo supports Dr. Splichal’s position:

The predominant theme of the training data analysis under unstable conditions is the striking reduction in force and, subsequently, power. It would be of no surprise then that the speed of motion, as well as the range of motion, were negatively affected under unstable conditions, as cited in the literature.

Reduced Force Outputs Result in Less Power

Essentially, even though both groups improved in some instances, the stable surfaces group outperformed the unstable group in all categories. So much so that it led the authors to conclude that the results of their study affirmed—what was a criticism then and now is fact—that unstable training does not allow for enough loading to create strength and data.

Simply put, athletes can handle heavier weight under stable conditions versus unstable conditions.

Dynamic Stability is critical for a skier or skater to assume a strong position from which to generate force while maintaining control and initiate precise movement from. A key marker of dynamic stability in ice skating and skiing is the magnitude of impulse force, especially peak force.

Impulse

Impulse is a large force applied for a short duration of time. Peak force is the highest force applied during an impulse force.

If superior dynamic stability is the reason for the dominance of racers like Hirscher and Shiffrin then pressure data obtained during skiing should show higher impulse and peak forces than generated their competition. While the technology to measure these forces is readily available I don’t have access to this data even if it does exist. So I’ll use data generated from hockey skate study I was involved in 2012 that compared data captured from competitive skaters performing in their own skates to skates I had modified using principles from my patents and modifications described in this blog.

The first step was to capture baseline data from the test subjects own ice skates (OS). The bar graph below shows the peak force in Newtons applied by each of the four test subjects. Peak force has a very short duration.

Subjects 1 and 3 applied a peak force of approximately 800 Newtons. A pound is 4.45 Newtons. So 800 Newtons is approximately 180 lbs.

Test subjects #1 and #3 are almost identical. But test subject #1 has a very slim edge over test subject #3.

Test subject #2 is 3rd in ranking while test subject #4 is last.

Assuming this was a study of competitive skier test subject #1 appears to have a stability advantage over the other skiers. This would translate into quicker more precise turns (hairpin turns) and less time on their edges.

In my next post I will show what happened when the same test subjects used the skates I prepared.


  1. Nailing the Coffin Shut on Instability Training Ideas – https://simplifaster.com/articles/instability-training/

 

THE HIRSCHER/SHIFFRIN HAIRPIN TURN EXPLAINED

The topics of interest in recent views of my blog combined with comments on online forums on ski technique where nebulous terms such as pressure and tipping are an integral part of the narrative, have highlighted the need for a uniform frame of reference as a basis for meaningful discussions of ski technique as well as for the analysis and accurate identification of factors that explain the superior technique of racers like Marcel Hirscher and Mikaela Shiffrin. Simply trying to emulate the moves of the great skiers without re-creating the equipment factors that enable superior performance is not a productive exercise.

I touched on some of the factors that enable Marcel Hirscher and Mikaela Shiffrin to dominate their competition in my posts WHY SHIFFRIN AND HIRSCHER ARE DOMINATING (1.) and WHY HIRSCHER AND SHIFFRIN CAN CROSS THE LINE (2.). Over the coming weeks, I will post on the factors that I believe explain the ability of Hirscher and Shiffrin to make rapid, abbreviated hairpin turns even on the steep pitches of a course using what I call the problem-solving matrix jigsaw puzzle format. In contrast to the linear step-by-step progression problem-solving format, the matrix jigsaw puzzle format lays out information relevant to a situation in a grid format much like a jigsaw puzzle.  Known factors are assembled where there is a fit with the interfaces and arranged in relation to other components until a solution begins to emerge much like a coherent picture begins to emerge in a jigsaw puzzle as the pieces are correctly assembled. As the picture becomes more clear, tentative connections between the known segments are hypothesized to try and extrapolate the big picture. As the process progresses, less certain or flawed information is discarded and replaced with more certain information

A lot of critical information on the neurobiomechanics and even the mechanics and physics of skiing is either missing, misapplied or misunderstood in the narrative of ski equipment and technique.

Biomechanics of Sports Shoes

A valuable reference on neurobiomechanics and the future of sports shoes is the technical text, Biomechanics of Sports Shoes by Benno M. Nigg. Used in conjunction with the chapter on the Ski Boot in the medical text, The Shoe in Sport, valuable insights can be gleaned on the mechanics, neurobiomechanics and physics of skiing.

Nigg’s book can be ordered at NiggShoeBook@kin.ucalgary.ca. The following chapters in particular contain information relevant to skiing:

3. Functional Biomechanics of the Lower Extremities (pp 79 to 123) – contains essential information on the human ankle joint complex, tibial rotation movement coupling and foot torsion.

4. Sensory System of the Lower Extremities (pp 243 to 253) – contains essential information on the sensory system responsible for balance and precise movement, both of which are key to effective skiing.

In order to advance skiing as a science, a mutual objective must be getting the right answer as opposed to a need to be right.

The wisdom of Albert Einstein is appropriate.

A man should look for what is, and not for what he thinks should be.

To raise new questions, new possibilities, to regard old problems from a new angle, requires creative imagination and marks real advance in science.

We cannot solve our problems with the same thinking we used when we created them.

If you can’t explain it simply, you don’t understand it well enough.

In my next post, I will start laying out the functional principles that I currently believe explain the factors that enable the superior performance of racers like Marcel Hirscher and Mikaela Shiffrin and their ability to rapidly redirect their line and maximally accelerate by making rapid, abbreviated, hairpin turns.


  1. https://wp.me/p3vZhu-2q3
  2. https://wp.me/p3vZhu-2qo

TIGHTLY FIT SKI BOOTS COMPROMISE SKIER BALANCE AND CONTROL

In reviewing recent articles on ski boot fitting I encountered the same perfect fit of the boot with the shape of the foot and leg and ski boots must be tightly buckled for good balance and control narrative fabricated decades ago to justify the interference with the actions of the joints of the ankle and leg created by the rigid plastic shell ski boot.

When the first rigid shell plastic ski boots were introduced, the field of biomechanics, as it exists today, was in its infancy. Even until recently, the human foot was modelled as a rigid block which was consistent with the shoe last theory and the theory that the perfect fit of ski boots with the foot and leg of the user is the best option for skiing. Further support for the support and immobilize theory came from the vilification of pronation arising out of the misapplication of Root’s Neutral theory (1.)

By the time the authoritative medical text, The Shoe in Sport, was published in 1987, the knowledge of the biomechanics of the human foot had progressed to the point where tight-fitting ski boots and loading the ankle joint were recognized as unphysiologic.

Few forms of athletics place as high demands on the footwear used in their performance as alpine skiing. It (the ski boot) functions as a connecting link between the binding and the body and performs a series of difficult complex tasks. (2.)

Investigations by Pfeiffer have shown that the foot maintains some spontaneous mobility in the ski boot. Thus the total immobilization by foam injection or compression by tight buckles are unphysiologic.(2.)

Many alpine skiers have insufficient mobility in their knees and ankle. The range of motion, particularly in the ankles, is much too small.(2.)

From a technical (skiing) point of view, the ski boot must represent an interface between the human body and the ski. This implies first of all an exchange of steering function, i.e., the skier must be able to steer as well as possible, but must also have a direct (neural) feedback from the ski and from the ground (snow). In this way, the skier can adapt to the requirements of the skiing surface and snow conditions. These conditions can be met if the height, stiffness, angle and functions (rotational axes, ankle joint (AJ)/shaft) of the shaft are adapted, as well as possible to the individual skier. (3.)

The articles on ski boots in the Shoe in Sport identified the objectives I was seeking in my efforts to design a ski boot based on principles of what is now referred to as neurobiomechanics. By the time I had formulated my hypothetical model of the mechanics, biomechanics and physics of skiing in 1991 I understood the need to restrain the foot in contact with the base of a ski boot and maintain the position of the foot’s key mechanical points in relation to the ski while accommodating the aspects of neurobiomechanical function of the foot and leg required for skiing. This was the underlying theme of the US patent that I wrote in February of 1992.

Existing footwear does not provide for the dynamic nature of the architecture of the foot by providing a fit system with dynamic and predictable qualities to substantially match those of the foot and lower leg. – US patent No. 5,265,350: MacPhail

On June 2, 2013 I published the post TIGHT FEET, LOOSE BOOTS – LOOSE FEET, TIGHT BOOTS (4.) in which I describe how attempts to secure the foot to a ski in a manner that interferes with the physiologic mechanisms that fascially tension and stiffen the structures of the foot that render it dynamically rigid actually reduce the integrity of the joint system of the lower limbs and hips resulting in a looser connection with the ski.

Studies done in recent years confirm the role of the active state of the architecture and physiology of the foot to postural control and balance.

These findings show that rather than serving as a rigid base of support, the foot is compliant, in an active state, and sensitive to minute deformations. In conclusion, the architecture and physiology of the foot appear to contribute to the task of bipedal postural control with great sensitivity. (5.)

The science of neurobiomechanics and the understanding of the mechanisms of balance and the role of the sensory system in human movement is accelerating. The time is long overdue for skiing to abandon it’s outdated concepts and align it’s thinking with the current state of knowledge.


  1. IS ‘SUBTALAR NEUTRAL’ SKIINGS’ HOUSE OF CARDS? – https://wp.me/p3vZhu-2mn
  2. Ski-Specific Injuries and Overload Problems – Orthopedic Design of the Ski Boot –  Dr. med. H.W. Bar, Orthopedics-Sportsmedicine, member of GOTS, Murnau, West Germany
  3. Biomechanical Considerations of the Ski Boot (Alpine) – Dr. E. Stussi,  Member of GOTS – Chief of Biomechanical Laboratory ETH, Zurich, Switzerland
  4. https://wp.me/p3vZhu-2K
  5. Foot anatomy specialization for postural sensation and control

SKIER BALANCE: IT’S ABOUT BALANCING OPPOSING TORQUES

The subject of my 4th post published on May 14, 2013 was the role of torques in skier balance. That this was one of my most important yet least viewed posts at 109 views suggests that the role of torques in skier balance is a concept foreign to skiers especially the authorities in the ski industry. This post is a revised version supplemented with information results from a recent study on balance control strategies.


While everyone recognizes the importance of good balance in skiing, I have yet to find an definition of what is meant by good balance, let alone a description of the neurobiomechanical conditions under which a skier is in balance during actual ski maneuvers. In order to engage in a meaningful discussion of balance, one needs to be able to describe all the forces acting on the skier, especially the opposing forces acting between the soles of the feet of the skier and the snow surface (ergo – applied and ground or snow reaction forces). Without knowing the forces involved, especially torques, any discussion of balance is pure conjecture. In 1991,  I formulated a hypothetical model that described these forces.  I designed a device with biomedical engineer to capture pressure data from the 3-dimensional forces (torques) applied by the foot and leg of the skier to the internal surfaces of the boot during actual ski maneuvers.

Test subjects ranged from Olympic and World Cup champions to novice skiers. By selectively introducing constraints that interfered with the neurobiomechanics of balance even a World Cup or Olympic champion calibre skier could be reduced to the level of a struggling beginner. Alternatively configuring the research device to accommodate the neurobiomechanical associated with skiing enabled novice skiers to use  balance processes similar to those of Olympic champions. To the best of my knowledge, no one had ever done a study of this nature before and no one has ever done a similar study since.

When analyzed, the data captured using the device called into question just about everything that is accepted as fact in skiing. This study was never published. For the first time I will present the data and describe the implications in future posts. We called the device shown in the photo the Birdcage. It was fully instrumented with 17 sensors strategically placed on a 3 dimensional grid.

Birdcage

The Birdcage instrumentation package was configured to detect coordinated neuromuscularly generated multiplane torques that oppose and maintain dynamic balance against external torques acting across the running surface of the inside edge of the outside ski in contact with the source of GRF (i.e. the snow).

  1. plantarflexion-dorsiflexion
  2. inversion-eversion
  3. external/internal vertical axial tibial rotation

Ankle torques are applied to the 3 points of the tripod arch of the foot (heel, ball of big toe, ball of little toe) and can manifest as hindfoot to rearfoot torsion or twisting wherein the forefoot rotates against the rearfoot.

A recent study (1.) on the role of torques in unperturbed (static) balance and perturbed (dynamic) balance found:

During perturbed and unperturbed balance in standing, the most prevalent control strategy was an ankle strategy, which was employed for more than 90% of the time in balance.

In both postures (unperturbed and perturbed) these strategies may be described as a single segment inverted pendulum control strategy, where the multi-segment system is controlled by torque about the most inferior joint with compensatory torques about all superior joints acting in the same direction to maintain a fixed orientation between superiorsegments.

The alignment of opposing forces shown in typical force representations in discussions of ski technique is the result of the neuromuscular system effecting dynamic balance of tri-planar torques in the ankle-hip system.

NOTE: Balance does not involve knee strategies. The knee is an intermediate joint between the ankle abd hip and is controlled by ankle/hip balance synergies.

The ankle strategy is limited by the foot’s ability to exert torque in contact with the support surface, whereas the hip strategy is limited by surface friction and the ability to produce horizontal force against the support surface.

Ankle balance strategies involve what are called joint kinematics; 3 dimensional movement in space of the joint system of the ankle complex. Contrary to the widely held belief that loading the ankle in a ski boot with the intent of immobilizing the joint system will improve skier balance, impeding the joint kinematics of the ankle will disrupt or even prevent the most prevalent control strategy which is employed for more than 90% of the time in balance. In addition, this will also disrupt or even prevent the CNS from employing multi-segment balance strategies.

Regardless of which strategy is employed by the central nervous system (CNS), motion and torque about both the ankle and hip is inevitable, as accelerations of one segment will result in accelerations imposed on other segments that must be either resisted or assisted by the appropriate musculature. Ultimately, an attempt at an ankle strategy will require compensatory hip torque acting in the same direction as ankle torque to resist the load imposed on it by the acceleration of the legs. Conversely, an attempt at a hip strategy will require complementary ankle torque acting in the opposite direction to hip torque to achieve the required anti-phase rotation of the upper and lower body.

Balance is Sensory Dependent

As a final blow to skier balance supporting the arch of the foot and loading the ankle impairs and limits the transfer of vibrations from the ski to the small nerve sensory system in the balls of the feet that are activated by pressure and skin stretch resulting in a GIGO (garbage in, garbage out) adverse effect on balance.

Spectral analysis of joint kinematics during longer duration trials reveal that balance can be described as a multi-link pendulum with ankle and hip strategies viewed as ‘simultaneous coexisting excitable modes’, both always present, but one which may predominate depending upon the characteristics of the available sensory information, task or perturbation.


  1. Balance control strategies during perturbed and unperturbed balance in standing and handstand: Glen M. Blenkinsop, Matthew T. G. Pain and Michael J. Hiley – School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK – Royal Society Open Science

SCHEDULE OF POSTS

The link below will take you to a page with a link to a PDF of all 298 posts I have made since my first post of May 11, 2013.

https://wp.me/P3vZhu-2sM

The schedule lists posts in the order of newest (Jul 10, 2018) to oldest (May 11, 2013). The image below shows what the schedule looks like. The date and time of the post and the views and likes are listed below the title of each post.

 

The top 10 posts to date are shown in the graphic below.

I am in the process of reviewing and analyzing post subjects based on ranking with the objective of better directing my efforts to my readers. If there are any subjects you would like addressed please post them in the comments section.

 

WHAT’S YOUR PQ? [PERFORMANCE QUOTIENT]

After my disastrous experience in 1977 with the mythical Perfect Fit with Crazy Canuck, Dave Murray (.1); one that transformed Mur from a World Cup racer to a struggling beginner, my work on ski boots became focussed on removing instead of adding material and making room to allow a skier’s foot to assume its natural configuration in the shell of the ski boot. As I improved the accommodation of a skiers’ neurobiomechanical functional requirements in the ski boot, skier performance improved in lockstep. I was merely reducing the structures of the boot that interfered with performance to enable a skier/racer to use the performance they already had.

Fit: The Antithesis of Human Function

Fit, by it’s definition of joining or causing to join together two or more elements so as to form a whole, is the antithesis (def: the direct opposite) of enabling the function of the human foot and lower limbs as one of the most dynamic organs in the human body. Fitting a ski boot to the foot and leg of a skier, especially a racer, equates with imposing a disability on them (2.). Although I didn’t realize it until I read The Shoe in Sport and learned of the barefoot studies done at the Human Performance Laboratory at the University of Calgary, my work on ski boots had transitioned from Fitting (disabling), by adding materials to liners to fill voids between the foot and leg and shell wall, to UnFitting (abling) by removing materials from liners and expanding and grinding boot shells so as to accommodate the neurobiomechanical functional requirements of the foot and leg of a skier.

But the big breakthrough for me came when Steve Podborksi won the 1981-81 World Cup Downhill title using the dorsal constraint system (Dorthotic) I developed and later patented. The Lange boot shells the device was used in had the least constraint of any ski boot I had ever worked with. The instantaneous quantum leap in Steve’s performance compared to the same shell using a conventional liner raised the question of how could a skier’s maximum performance be achieved and was there a way to compare to a skier’s performance in different ski boot/liner configurations to an optimal reference standard?

A reliable indicator that my un-fitting was trending in the right direction was that skiers consistently found that skiing became easier. For racers, coaches would typically report that the racer was skiing better. Improved race results served as further confirmation of my efforts. But these indicators were subjective. I wanted a way to not just measure performance with quantifiable metrics generated from data specific to the activity, I wanted to be able to compare the same metrics to a reference or baseline standard that represented the optimal performance of a skier or racer at a given moment in time. Without a way to measure and compare performance there is no way of knowing how a ski boot is affecting a skier or racer and especially no way of knowing how close they are to skiing at their maximum level of performance. I wanted to develop a skier Performance Quotient or PQ.

Definition of Quotient

  • Mathematics: – a result obtained by dividing one quantity by another.
  • a degree or amount of a specified quality or characteristic.

A skier Performance Quotient would capture baseline metrics from a skier’s performance in a ski boot that provides the optimal functional environment for the foot and lower limbs to the skier’s peformance in different ski boots including a skier’s current ski boot. The ski boot that provides the optimal functional environment for the foot and lower limbs would be designated as 100%. If the same metrics captured in a different ski boot were 78% of the reference standard, the skier’s PQ in the ski boot would represent a PQ of 78% against a possible 100% or 78/100.

Raising the bar of skier/racer function with body work and/or conditioning will raise the PQ. But it cannot close the PQ gap created by the performance limitations of the interference with neurobiomechanical function caused by their ski boot. Nor can trying harder or training more intensely overcome the limitations of a ski boot. Assuming 2 ski racers of equal athletic ability and mental strength, the racer with the ski boot that enables a higher PQ will dominate in competition. The only way to improve a skier’s PQ when it is less than 100% is to improve the functional environment of the ski boot.

In current ski boot design process, manufacturing and aesthetic considerations override skier functional requirements. An innovative approach to the design of the ski boot is needed. This is the subject of my next post.


  1. IN THE BEGINNING: HOW I GOT STARTED IN SKI BOOT MODIFICATIONS, May 12, 2013 – https://wp.me/p3vZhu-y
  2. LESS REALLY IS MORE, May 13, 2013 – https://wp.me/p3vZhu-N