Lee Saxby's Wisdom of Coaching Blog

The Zombie Diet


Torpor is a state of decreased physiological activity in an animal, usually by a reduced body temperature and metabolic rate. Torpor enables animals to survive periods of reduced food availability. A torpor bout can refer to the period of time a hibernator spends at low body temperature, lasting days to weeks, or it can refer to a period of low body temperature and metabolism lasting less than 24 hours, as in “daily torpor”.

From Wikipedia, the free encyclopedia

Human beings are homeotherms. Maintaining a consistent body temperature of between 36 to 38 degrees is a homeostatic requirement for optimal enzyme function and metabolic health (fig 1). Poikilotherms will have four to ten enzyme systems that operate at different temperatures but because their metabolism is variable and generally below that of homeothermic animals, maintaining a large brain is generally beyond poikilotherm animals. The metabolism of poikilotherms favors strategies such as ambush hunting rather than stalking-sprinting or persistence-endurance type hunting with it’s high movement cost. As they do not use their metabolisms to heat or cool themselves, total energy requirement over time is low and for the same body weight, poikilotherms need only 5 to 10% of the energy of homeotherms.



A consistently low-morning-body temperature is associated with ageing and chronic stress and is a symptom of overtraining syndrome (OTS) in endurance athletes (fig 2).


Aside from unintelligent training behaviour (see BTR training zones), the biggest influence on ‘homeothermic ability’ is eating behaviour and nutrition. The low–carbohydrate diets and ‘intermittent fasts’ that are gaining popularity amongst the ‘barefoot running’ and ‘natural movement’ communities create stressful levels of gluconeogenesis that reduce the liver’s ability to convert circulating levels of inactive-thyroid hormone (T4) to the active form (T3). The amount of circulating T3 in the body is the biggest influence on cellular metabolism and heat production (thermogenesis). The low levels produced by the liver during fasting and low-carbohydrate dieting are responsible for the reduced Basal Metabolic Rate (BMR) observed in each phase of yo-yo dieting.

A low-carbohydrate diet invariably implies a high fat intake and/or high protein intake which, in western society, invariably implies a high PUFA (polyunsaturated fat) intake (fig 3) due to modern-industrialised-agricultural methods. The ‘essentiality’ of PUFAS (both omega 6 and omega 3) is open to debate but the physico-chemical realities of the autoxidation rates and free radical production of highly unsaturated oils at mammalian body temperatures is not (fig 4).



When the metabolic ‘insult’ of excessive lipoprotein oxidation (rancidity) due to high PUFA intake is added to the metabolic ‘injury’ of excessive gluconeogenesis created by low-carb dieting and fasting, the normally-stable homeothermic ability of mammalian physiology becomes unstable, and body temperatures can drop dramatically in response to environmental temperatures, leading to torpor and hibernation (fig 5).



BTR Considers the combination of low-carbohydrate intake, intermittent fasting and high PUFA intake is the perfect diet plan for Zombies (fig 6).



Barnes BO, Galton L (1976)  Hypo-thyroidism: The Unsuspected Illness

Meerson FZ (1983) Adaptation, Stress and Prophylaxis

Mackenzie MA et al (1991) Poikilothermia in Man: pathophysiology and clinical implications. Medicine (baltimore)

Kreher JB, Schwartz JB (2012) Overtraining Syndrome: A practical Guide. Sports Health

Frank CL (1992) The Influence of Dietary fatty Acids on Hibernation by Golden-mantled Ground Squirrels. Physiological Zoology

Cramer DL, Brown JB (1943) The Component Fatty Acids of Human Depot Fat. Journal of Biological Chemistry

Geiser F (1990) Influence of polyunsaturated and saturated dietray lipids on adipose tissue, brain and mitochondrial membrane fatty acid Composition of a mammalian hibernator. Biochimica et Biophysica Acta

Carey HV et al (2003) Mammalian Hibernation: Cellular and Molecular Responses to Depressed Metabolism and Low Tempertaure. Physiol rev

Ayre KJ, Hulbert AJ (1997) Dietary fatty acid profile affects endurance in rats. Lipids

Hulbert AJ et al (2010) Membrane fatty acid composition and longevity of mammals and birds. Research Online

Hulbert AJ  et al (2005) Dietary fats and membrane function: implications for metabolism and disease. Research Online

Zombie sleep patterns

‘Tis sleep that knits up ravell’d sleeve of care, the death of each day’s life, sore labours bath, balm of hurt minds, great nature’s second course, chief nourisher in life’s feast’

Macbeth, William Shakespeare

Def. a zombie runner is a runner with a de-energised brain (see our earlier post Zombie Runners).

Each species requires a different amount of sleep each day to maintain good health (fig 1).  On average, a young-adult human requires 8 hours a day that gradually declines to 6.5 hours a day when elderly. The inability to go to sleep (insomnia) and/or remain asleep (dyssomnia) are classic signs of stress and ‘over-training’.


There are many possible biological, psychological and social reasons for disturbed sleep patterns, but one cause that is frequently over looked in runners is deficient-night-time-liver-glycogen levels. The period of time we are asleep is known as an ‘over-night fast’ which in young, healthy adults occurs in two distinct phases (fig 2):



Stage 1: Glucose for the brain is provided almost exclusively by the breakdown of liver glycogen (depending on the timing of the last carbohydrate meal)

Stage 2:  As liver glycogen depletes, cortisol begins to rise, breaking down proteins (amino acids) in muscle (and thymus-lymphatic tissue) to maintain blood glucose via gluconeogenesis. In the healthy-well-fed liver, glycogen stores are never fully depleted, and the additional glucose provided by gluconeogenesis is enough to ensure a peaceful, undisturbed 8 hours of sleep (fig 3a). If liver glycogen stores are not fully replenished before attempting to sleep, either due to illness or unintelligent eating and training behaviour, the liver glycogen stores will be inadequate to maintain blood glucose through the night, causing an early and exaggerated cortisol response and increased gluconeogenesis. If blood glucose falls below homeostatic requirements of the brain, an ‘emergency’ adrenalin response occurs to ‘squeeze’ some extra glucose into the blood from the glycogen stores in the liver.

This rapid rise in adrenalin creates a classic ‘fight-or-flight’ stress response of increased arousal (increased cardiac output and respiration) which makes sleep impossible until the circulating adrenalin has returned to normal (fig 3b).


The ability to sleep for 7-8 hours each night is a homeostatic requirement for homo sapiens, and sleep disturbances are a reliable indication of Over Training Syndrome (OTS) and chronic stress. A basic understanding of the liver’s role as the ‘glucostatic’ organ, and how to restore and support it’s function, is essential knowledge for anyone involved in training athletes, and is considered an essential part of the BTR bioenergetics education.


Cannon. W. (1932) The Wisdom of the body

Frayn K N. (1996) Metabolic Regulation: A human perspective

Armstrong L.E., VanHeest J.L (2002). The Unknown mechanism of the Overtraining Syndrome. Sports Med

Scheer et al (2010) Impact of the human circadian system, exercise, and their Interaction on cardiovascular function. PNAS

Macauley et al (2015) Diurnal variation in skeletal muscle and liver glycogen in humans with normal health and type 2 diabetes. Clinical science.

Zombie Runners


“The third or chronic form of general fatigue is found in men during a course of training in which the amount of endurance required daily is more than can be regained during the periods of rest. In this condition the temperature becomes subnormal, the weight goes down, the skin looks pale and flabby, the muscles lose their elasticity, the eye becomes dull and listless, interest in exercise ceases, every effort becomes a burden, and the patient sits without ambition or the power to rouse himself from his lethargy”

Exercise in Education and Medicine by Robert Tait McKenzie, B. A., M. D (1909)

zombie-runner-fig1The human brain is three times the size of an ape’s relative to body size (fig 1). It accounts for 20-25% of an adult’s resting oxygen and energy use, and 60-70% of total-body-glucose metabolism. This makes the human brain the most ‘expensive’ metabolic tissue found within all known species, and one of the most vulnerable to metabolic ‘stress’, especially during it’s growth and development (fig 2).

Despite it’s reliance on a constant supply of glucose, the brain stores only a tiny amount locally as glycogen*, so relies on the ‘glucostatic’ function of the liver (80-90% of circulating glucose comes from the liver) to maintain an adequate glucose supply. Brain function is compromised when blood glucose falls below (hypoglycemia), or exceeds (hyperglycemia), the normal physiological range (70-110 mg/dl). Consequently, humans have evolved a number of metabolic ‘emergency’ strategies to ensure the survival of the brain, often to the detriment of the rest of the body.


The progression of ‘Over Training Syndrome’, due to unintelligent-endurance training (see BTR Training Zones), shares many features with the progression of glucose starvation (fig 3). The ‘raiding’ of vital-structural and immune-system proteins, combined with the attempt to metabolise inferior ‘energy’ substrates (lactate, amino acids, and fatty acids), creates the physiological and psychological symptoms of Hysteria, Neurasthenia, Hypochondriasis, Malingering, Pyschoneurosis, Depression, Chronic Fatigue Syndrome (CFS), Myalgic Encephalopathy (ME), Post-Viral Fatigue Syndrome (PVFS), Under Performance Syndrome (UPS) and Over Training Syndrome (OTS).

These labels are historically and culturally dependent, but would appear to boil down to one thing; a de-energised brain.


* For every 1 gram of glycogen stored, 3 grams of water is stored with it so for the brain to store 100g of glycogen (the amount stored in the liver) it would weigh an additional 400g. The extra weight (and volume) would completely change the morphology and function of the human body.


Ruderman NB, Aoki TT, Cahill GF. (1976) Gluconeogenesis and its disorders in man. In Gluconeogenesis: Its Regulation in Mammalian Species.

SC Kalhan and IÁ Kilic (1999) Carbohydrate as nutrient in the infant and child: range of acceptable intake. European Journal of Clinical Nutrition.

Taylor RE (2001) Death of neurasthenia and it’s psychological reincarnation. British Journal of Psychiatry.

Lewin R. (1984) Human Evolution: An illustrated Introduction.

Muhammad Z. Shrayyef and John E. Gerich (2010) Normal Glucose Homeostasis: in Principles of Diabetes mellitus. L. Porestky (ed)

The bioenergetics of running

“Three things are needed to build and maintain a living system: material, information (pattern), and energy. There is no life without energy”

Albert Szent-Györygi The Living State (1972)

runner-pic1‘It has always been my view that a knowledge of physiology and biochemistry makes exercise more interesting for a runner. The current running boom (for some almost an addiction, but if so the only healthy addiction I know) makes necessary for the intelligent runner to know more  about his body, how hard he should train, when he should yield to fatigue and what should be his diet and what are the limiting factors of his performance…’ Sir Roger Bannister MD.

The BTR bioenergetics education has been designed in the same spirit as the BTR biomechanics education; with the intention of providing a small island of coaching wisdom in a ‘boggy’ area notoriously flooded with information i.e. training and diet.

‘The Runner’ by Eric Newsholme and Tony Leech was the starting point in the creation of BTR’s ‘bioenergetics’ and although first published in 1983 the knowledge contained within this small book and it’s 150 pages is still very relevant today (as the preface from Sir Roger Bannister above indicates). Here are a few examples of the simple Figures used and BTR’s interpretation of them.


Running A Marathon:

runner-pic2A healthy-human body contains enough stored glucose (glycogen) to provide energy for approximately 90 mins of running. Consequently, the body must use an alternative fuel source to provide energy for runs of longer duration. The substrate of choice is fatty acids. (*Gluconeogenesis from structural proteins is an ‘expensive’ option that the body will try to avoid whenever possible)

The ‘Wall’:

runner-pic3Up to the 17th-18th mile, the average runner has been oxidising both fatty acids and glucose. The muscle glycogen stores are now depleted, and fatty-acid oxidation cannot provide ATP at the rate required to maintain the desired muscle action and running speed, consequently the pace drops and the pain increases.

Fatty acids; A vicious cycle:

runner-pic4Using fatty acids as as a fuel is a ‘survival’ strategy designed to conserve enough liver glycogen to prevent hypoglycemia and maintain brain function. The glucose-sparing effect of fatty acid oxidation observed in well-trained distance runners is also consistently observed in shock, starvation, heart failure and diabetes and is known as the ‘Randle cycle’.

Rehabilitating the Human Foot – part 1

A fundamental principle of the BTR ‘Bulletproof’ running system is that the benefits of changing running technique are directly related to the function of the human foot.

The human foot not only plays an important mechanical role in locomotion (providing stability and elasticity) it also plays a vital sensory role. Both these functions are compromised through poor footwear choices.

Anatomically Intelligent Footwear can be effective in rehabilitating feet back to a Natural (see GOOD in the BTR Good, Bad, Ugly series) state, only if:

  1. the footwear is correctly sized to allow for “expansion” of the foot when loaded, as the diagrams below show
  2. when socks are worn, they are not tight
  3. the wearer has significant time on feet (standing, walking, running) each day.




The Good, The Bad, The Ugly PART 3: Feet

‘The human foot is a masterpiece of engineering

Leonardo Da Vinci

Natural foot function is literally the foundation of efficient, injury-free running and identifying potential structural or ‘hardware’ problems is an essential part of the BTR system (form determines function) and the ability to recognise basic foot ‘shapes’ (foot morphology) is a good place to start.


BTR-foot-goodDef. the foot-shaped foot. Also known as the ‘natural’ foot as it is the foot shape observed in unshod populations and new-born babies (read Myth of the Hereditary Bunion post). Also referred to as a ‘flexible-flat foot’ in the podiatric literature.

Even rarer than ‘good’ running technique in modern-industrialised societies due to the established paradigm of footwear design and the incredible ‘plasticity’ of the human foot.

Based on simple physics; a ‘good’ foot provides a wide, stable platform for all functional-human movements including; standing, squatting, lifting, walking and running. The ultimate goal of the BTR “bulletproof’ running system is to match a ‘good’ foot with ‘good’ running technique (matching the hardware with the compatible software)


BTR-foot-badDef. the flat foot. The ‘bogeyman’ of podiatric science and the pathology driving the insole/orthotics industry. Contrary to podiatric dogma; a ‘true’ flat foot (arch flat against the floor whilst standing) is actually quite rare within the healthy, pedestrian population (people that are still able to walk and run).

Anecdotal observations (n= > 1000) within the BTR coaching community suggest that over 90% of runners diagnosed as having ‘flat feet’ and using corrective insoles actually present ‘ugly feet’ with high-rigid arches and weak, over-pronated ankles.

Either there is an epidemic of cretinism amongst the podiatric profession or the prescribed orthotics/insoles are creating an epidemic of ‘ugly’ feet.


BTR-foot-uglyDef. the shoe-shaped foot. Also known as a ‘normal’ foot as it is the most common foot morphology in modern, shod populations.

The ‘ugly’ foot is not only compromised in ‘form’ but also in ‘function’, it’s structural instability (and lack of elasticity) is probably the primary reason for the ‘mysterious’ epidemic of chronic-running injuries prevalent in modern society.

BTR coaches are trained to identify this foot morphology and can explain to would-be ‘natural’ or ‘barefoot’ runners with ‘ugly’ feet why the risks of removing or reducing the amount of shoe far outweigh the perceived benefits. This foot has adapted to many years of wearing anatomically-inappropriate footwear and consequently cannot function adequately without it.

The Good, The Bad, The Ugly PART 2: Squatting

“A ship is safe in harbor, but that’s not what ships are for”

William Shedd

real-squatIf there is one exercise that runners should become obsessed about, it is the deep squat. It is no coincidence that the naturally-resilient-running populations discussed in PART 1 not only have ‘foot-shaped feet’ but also regularly adopt a deep-squatting posture as a ‘rest position’ for all sorts of daily activities. These people are not super human but have simply  maintained the squat position that all humans use until 3-5 years old, before the culture of chairs and sitting began to take over. (see The Human Sea Squirt)


BTR-SQUAT-GOODDef. The habitual-squatting position of homo sapiens.

This position should not be considered an ‘athletic’ position, but rather a fundamental human movement akin to standing and walking. The ability to adopt the ‘good’ deep-squat position indicates healthy ankle, knee and hip function and has many benefits for runners, including the development and maintenance of full range of motion (ROM) in the joints required for ‘good’ running technique. The ‘good’ deep squat is a fundamental motor skill milestone for BTR, and mastering this skill is an essential part of the ‘Bulletproof Runner’ protocol.


BTR-SQUAT-BADDef. The habitual squatting position of homo sedentarius, endorsed by chartered physiotherapists and certified personal trainers worldwide as the ‘safest’ way to squat.

The ‘bad’ squat appears ‘safe’ due to the limited range of motion required at the ankle, knee and hip to perform this movement, but when these limitations (known as ‘sagittal blocks’) manifest in dynamic-human movements such as jumping, walking and running, the body compensates with unnatural movement strategies and destructive loading patterns e.g. over pronation and over striding (see overstriding).


BTR-SQUAT_UGLYDef. The habitual-squatting position of homo neanderthalensis and ‘cross-fitters’.

The ‘ugly’ deep squat is the equivalent of the ‘ugly’ running style (see good bad ugly part 1) in that it is performed and coached with good intentions, but probably causes as many problems for runners as the ‘bad’ squat. The limited range of movement (ROM) at the ankle joint (observe the knee position relative to ankle position in the diagram left) means that compensatory movement must occur in the lumbo-pelvic region in order to adopt a deep-squatting position. The compromised alignment of the ‘ugly’ deep squat places the pelvis and lower back in an extremely-vulnerable position where the addition of extra weight and/or higher velocities (weightlifting and plyometric routines) will invariably add a ‘bad back’ to your list of ‘running injuries’.

The Good, The Bad, The Ugly PART 1: Running Technique

‘God, grant me the serenity to accept the things I should not change,

The courage to change the things I can,

And the wisdom to know the difference’

The Serenity Prayer – Coaches Anonymous


There are three main characters that appear in almost all running technique stories; the good, the bad and the ugly.

The ‘good’

BTR-running-GOODRarely seen outside the developing world, except in BBC documentaries and televised athletic events, this runner is Mother Nature’s poster boy (or girl) for natural function.

The defining characteristics of an upright posture, relaxed rhythm and animal-like elasticity are found in the best of natural runners such as the Tarahumara, the Bushmen and the East Africans and contribute to their legendary speed, endurance and resilience against injury. In fact, this running style is probably the signature movement pattern for homo sapiens, and it would be logical to assume that the benefits associated with adopting it should outweigh any inherent risks.

Unfortunately, as all BTR coaches know most ‘beautiful hypotheses’ are ruined by ugly facts and in this case the ugly fact is the modern shoe-shaped foot.


The ‘bad’

BTR-running-BADInstantly recognisable to coaches and runners alike by their heel-striking, slumped posture and overstriding-shuffling gait.

This much maligned character is held responsible for virtually all running-related evils in the world and most running technique and natural movement coaches have sworn a solemn oath to eradicate this breed from the face of the earth. BUT like all complex, supposedly-evil characters, they often display redeeming features (brutal dictators who are kind to animals etc) which should be taken into account. The ‘bad’ runner can often display a skillful-pendulum type running style that is efficient and enables them to cover a lot of miles without injury (in fact, this is the most common running technique adopted by ‘good’ ultramarathon runners).

There is a lot of wisdom in the old adage ‘if it ain’t broken, don’t fix it’ which definitely applies to this character and as all BTR coaches know the ‘risk-to-benefit’ ratio of changing running technique should always be in the forefront of your mind.

The ‘ugly’

BTR-running-UGLYSince the heady days of the ‘barefoot revolution’ which began in 2010, this character has been showing its ugly face at coaching venues around the world and ruining the simple and elegant ‘good’ vs ‘bad’ story being delivered.

This character epitomizes the ‘self-educated’ runner who has read everything in the blogosphere and in the running tabloids re: ‘good’ running technique and ‘knows’ they are running correctly. In my experience, these runners are just as broken as ‘bad’ runners and are particularly prone to chronic-lower-limb injuries such as achilles tendonitis and plantar fasciitis. The skill of running resides in the sub-conscious mind and ‘over-thinking’ creates tense, rigid and over-exaggerated movement patterns and a brave new world of pain and dysfunction.

What you ‘think’ you’re doing and what you are ‘actually’ doing are often poles apart, and this is where a running coach with a trained, experienced eye armed with a video camera of at least 60fps becomes the ultimate ‘beauty therapist’ for runners.

The Myth of the Hereditary Bunion

“They fuck you up, your mum and dad.
They may not mean to, but they do.
They fill you with the faults they had
And add some extra, just for you.”

This Be The Verse by Philip Larkin


A frequent comment from coaching clients (usually women) is that they have hallux valgus (bunions) because their parents and grandparents have them i.e. it is inherited.

It’s easy to see why somebody would say that with confusing statements like this from the American College of Foot and Ankle Surgeons website:

Causes – Bunions are most often caused by an inherited faulty mechanical structure of the foot. It is not the bunion itself that is inherited, but certain foot types that make a person prone to developing a bunion. 

This statement could be rewritten as:

Causes – Bunions are most often caused by the habitual routine of forcing an inherited wide forefoot into a narrow shoe. It is not the bunion itself that is inherited, but certain foot types that make a person prone to developing a bunion.

Here are some of the many papers linking inappropriate footwear with foot deformities:

“Examine the feet of young children before they have been crippled by shoes. Observe how distinct and separate each toe is: no one crowding its neighbor, the great and lesser toes in line with their metatarsals, and the inner border of the foot a straight line. The long axis of the great toe prolonged backward will, in the normal foot, (he means natural) strike about the center of the heel. That this condition would continue throughout life in an unhampered foot is proved by the shape of adult feet among barefooted races.” Hoffman (1905).

Sim-Fook and Hodgson (1958) examined Chinese in Hong Kong and found hallux valgus in 1.9% of the barefoot and in 30% of the shoe-wearers. Their investigation was prompted by statements that foot deformities are hereditary and develop in people who have never worn shoes. Their conclusions:

“The foot in its natural unrestricted form is mobile and flexible without any of the static complaints often encountered. When the foot foot becomes restricted by the wearing of stockings and shoes, its natural form become altered and static deformities develop.

I.B. Shine (1965) was a medical officer to the island of St. Helena who made a survey of the incidence of hallux valgus amongst the islander’s shoe-wearers and also those who were habitually barefoot.

“This study shows that hallux deviation greater than 15 degrees was present in 2% of the barefoot, and in 16% of the men and 48% of the women who had worn shoes for 60 years. As the rise in incidence is linear, and as it cannot be attributed to age, social class, occupation, or exercise habits, it is likely that the increase is a direct effect of wearing shoes.

Kato & Watanabe (1981) showed that the decline of the traditional Japanese “geta” clog and increased wearing of western style leather shoes in the 1960’s and 1970’s, correlated to increased reporting of hallux valgus.

“Until recent years, hallux valgus did not exist in Japan. Changing customs and styles of footwear during the past ten years have led to an increasing number of patients with the classic hallux valgus deformity. These are not mild deformities, but are painful and require surgical correction. The ratio of the width to the length of the foot is similar in both sexes and was measured in children up to the age of 14. Coincidentally, at about that time students may freely wear any type of fashionable shoe. We conclude, therefore, that the hallux valgus deformities we are now seeing with greater frequency are caused, at least in part, by the change in footwear.”

Returning to the comments of my coaching clients. Given the weight of evidence for the effect of footwear on foot shape, it is more likely that footwear choices are inherited and that the lifelong habit of wearing inappropriate footwear within a family leads to both parents and their offspring suffering from the same structural deformities.

It’s time for parents to adopt BTR’s Anatomically Intelligent Footwear criteria when choosing footwear for their little ones and to break the cycle of Philip Larkin’s poem.


Hoffman, P. 1905. Conclusions drawn from a comparative study of the feet of barefooted and shoe-wearing peoples. The Journal of Bone and Joint Surgery, 3, 105-136.

Lam Sim-Fook and Hodgson, A. R. 1958.  A comparison of foot forms among the non-shoe and shoe-wearing Chinese Population. 7. Bone 7t Surg., 40A, 1058.

Shine, I. B. 1965. Incidence of hallux valgus in a partially shoe-wearing community. British Medical Journal, 1, 1648-1650.

Kato, T. and Watanabe, S. 1981. The etiology of hallux valgus in Japan. Clinical Orthopedics and Related Research, 157, 78-81.

‘Overstriding’ and the effects of changing stride frequency

“Science is the attempt to make the chaotic diversity of our sense experience correspond to a logically uniform system of thought.”

Albert Einstein

‘Overstriding’ (foot position on initial-ground contact too far forward relative to the runner’s general centre of mass) is widely accepted within the sports medicine community as a risk factor for running injury and poor performance. The established coaching solution is to increase stride frequency using a metronome to a cadence of 180bpm. The latest research by Dan Lieberman and his team at Harvard attempts to qualify ‘overstriding’ and quantify the effect of changing stride frequency on impact peaks and running economy.

The results of this study have huge implications for running-technique coaches. Our summary of Dan Lieberman’s paper can be found HERE.

BTR’s take home message for coaches:

1. overstriding at the hip



  • Caused by excessive hip flexion
  • Increases as cadence decreases
  • Creates increased braking force
  • Increased joint torques at ankle, knee, hip and sacroiliac joint
btr-chair-slouch BTR considers the primary cause of this type of ‘overstriding’ to be chairs and habitual seated postures.

2. Overstriding at the knee



  • Caused by excessive knee extension
  • Creates increased GRF impact peaks
  • Consequently disproportionate Increase of joint torques at knee = increased risk of knee injury




BTR considers the primary cause of this type of ‘overstriding’ to be cushioned shoes.

Read our pendulums & springs post.

3. economy: stride rate v. overstriding

The metabolic cost of ‘swing phase’ is primarily due to Maximum Hip Flexion Moment (MHFM) i.e. the muscle activity required to overcome momentum and create the ‘swing’.



The metabolic cost of an ‘overstride’ is due to the braking impulse that decelerates the body during the first half of stance i.e. the muscle activity required to counteract gravity and Ground Reaction Force (GRF) (Read our extensor paradox pt2 post).

Dan’s study found that 170 seems to be the average energetic optimum when running at a speed of 3.0ms on a treadmill


BTR considers the ‘sweet spot’ to be a stride frequency of 170-185 in SKILFUL runners. The stride frequency varies within this range due to speed, body weight, age and terrain.


Lieberman, D.E., Warrener, A.G., Wang, J. and Castillo, E.R. (2015). Effects of stride frequency and foot position at landing on braking force, hip torque, impact peak force and the metabolic cost of running in humans. Journal of Experimental Biology, 218, 3406-3414

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