Arugula - Not Just Good for Salad!

Arugula is known for as being a tangy salad green, but it is also a relative of the cruciferous family, which includes radishes, Brussels sprouts, kale, cauliflower and broccoli.   Like these foods, arugula has many highly beneficial nutrients that include anti-cancer compounds and carotenoid anti-oxidants that help eyesight.

These beneficial plant chemicals include flavonoids that improve blood vessel function, increase blood flow, lower blood pressure and lower inflammation. Arugula can also help to counteract the negative effects of heavy metals and helps eliminate pesticides from the body.

Research shows that the trace minerals and antioxidants arugula contains can block the absorption of environmental contaminants suspected of impacting your libido.

Arugula and Nitric Oxide

Arugula contains the highest levels of nitrates of any plant, and nitrates are used to produce nitric oxide (NO) in the body.    NO is a very important signaling molecule that supports healthy endothelial (blood vessal lining) function and protects the mitochondria of the cells. 

  

Arugula contains about 480 milligrams (mg) of nitrates per 100-gram serving compared to 281mg for rhubarb, cilantro at 247, and 110mg for beets.  Spinach also contains high levels as do all green leafy vegetables which is thought to be why their consumption helps prevent heart attacks, stroke and heart disease.

High Nitrate intake boosts NO directly.   NO relaxes and widens blood vessels dramatically increasing blood flow and oxygenation of your tissues.  This increases the body’s ability to carry away waste material and carbon dioxide.  A diet high in nitrates can help prevent and treat high blood pressure in this manner.

Although raw beets are the best-known vegetable for boosting NO, increasing circulation and lowering blood pressure arugula is the real king.

Nitrates, NO and Exercise Capacity and Endurance

Nitrate intake and increased NO in the body has been proven to dramatically increase exercise capacity and endurance, and the drug Viagra functions by boosting NO levels which is the drug treatment for male impotence.  So a healthier heart, lower blood pressure and increased exercise capacity are not the only reasons to increase your intake of Arugula!

How to Optimize the Benefits of Vitamin D Supplementation

Vitamin D is constantly in the news lately and for good reason.    Optimal levels of Vitamin D have been linked to a host of benefits including prevention and treatment of many key diseases ranging from Osteoporosis to improved heart health with reduction in heart attack risk to prevention of many different types of cancer.

The ideal way to get optimal levels of Vitamin D is to let your body create it through Safe Sun Exposure (see previous blog on this subject here:  http://workoutanytime.blogspot.com/2016/08/the-facts-on-safe-sun-exposure-and.html  However this is easier said then done, and too much sun is clearly a strong risk factor for skin cancer!      Enter Vitamin D supplementation.

The amount and form of Vitamin D supplementation has changed substantially based on lots of emerging research.    The form that should be taken is Vitamin D-3 NOT D-2 form and all experts agree on this!     However when it comes to dosage things get much trickier.      The confusion comes because Vitamin D is really a powerful compound and functions as a hormone in the body.    As such it has profound impact on virtually every system in the body.    In addition you can overdose on Vitamin D supplements so more is NOT always better!

Ideally you should order a blood test and test your levels.    The test you want is called a 25(OH)D blood test and is offered by all major labs.   You can either ask your doctor to order this test for you OR you can order an in-home test.   You just prick your finger and put a drop of bloo on the enclosed paper and send back in to the labs.    You can also your own blood test online and go to a lab to have blood drawn in the same way your doctor orders the test.   For more information on testing go here:  https://www.vitamindcouncil.org/testkit/?gclid=Cj0KCQjwh_bLBRDeARIsAH4ZYEPhv0MVkO5_S7USZZ8bwVlt5A3vPWGbBFFIbJiB8Wtva0x-IDH7UmQaAlGkEALw_wcB#

Ideal versus Acceptable Blood Levels of Vitamin D

There is a big difference between what is considered “acceptable” or okay and ideal blood levels.   Here are the classifications of different blood levels of Vitamin D. according to the Vitamin D Council:

0 – 30 ng/ML is very low and considered a deficiency

30 – 39 ng/ML is better but still insufficient for optimal health and disease prevention.

40 – 100 ng/ML is optimal

Above 150 ng/ML is toxic!

The key is to test and if low take a supplement then retest 2 – 3 months after regular vitamin d use because each person is different in how much supplementation they need based on many factors including sun exposure and skin type.     The RDA for Vitamin D for infants is 400iu.    For Children 1 – 13 and adults through age 70 the RDA is 600iu and for those over 70 the RDA is 800iu.

Unfortunately, this is way too low to get many people into the sufficient much less optimal range so testing is really worthwhile.   In many cases people need 4,000 – 10,000 or more iu's per day for at least a month to get where they need to be for optimal health!

Preventing Vitamin D Toxicity through the Co-Administration of Vitamin K-2

Like many vitamins Vitamin D has a co-factor or other vitamin that helps it perform its function better and in a more balanced fashion, and that other vitamin is Vitamin K-2 (not to be confused with K-1 found in many plants).    In an ideal world, you can get all the Vitamin K-1 you need from eating plenty of green, leafy vegetables, and your body can turn it into K-2.   Unfortunately, this conversion is lacking in many people.

More importantly K-2 is not easily toxic and can be taken with Vitamin D.    K-2 is best taken as a supplement as MK-7 version which has been heavily researched and shown to improve bone health and prevent arterial calcification which can potentially occur with too much Vitamin D.     For a more complete understanding behind how K-2 works with Vitamin D and why it is a great idea to take the MK-7 form of K-2 with Vitamin D check out this article from Dr. Mercola:   http://articles.mercola.com/sites/articles/archive/2011/03/26/the-delicate-dance-between-vitamins-d-and-k.aspx

Taking 100 – 200 mcg per day of Vitamin K-2 will help optimize the effects of Vitamin D and minimize risks associated with Vitamin D Supplementation.

The Nordic Hamstring Curl: Best Hamstring Exercise You are Not Doing!

There are many different hamstring exercises including variations of leg curls (seated, prone, and standing) along with several different hip hinge exercises that target the hamstrings (RDL, Single Leg RDL, etc).     These are all great exercises, but none of them can touch the Nordic Hamstring Curl for building eccentric strength and preventing hamstring injury in sprints and sport!

This is a tough exercise so warming up the hamstrings is essential.  Using other hamstring exercises first such as bodyweight hip hinges and light leg curls on a machine prior to this exercise do the trick nicely.   It is also a good idea to do some static stretches for anterior hips and hip flexors to shut them off which helps to allow for maximum hamstring activation.

To perform the Nordic Hamstring Curl you need to find a place to hook your heels under when you are in a double leg tall kneeling position so you will also need padding under your knees.     If you have a workout partner you can have them kneel behind you and hold onto both your legs right above the ankles keeping their arm straight so they can use their bodyweight to apply load as you let your body fall forward like this:   http://willlevy.com/wp-content/uploads/2014/08/Nordic-Curl.jpg .     You can also find something to hook your ankles under like the horizontal bar from a weight machine or barbell like this:   https://i.ytimg.com/vi/f_GdZKdwovA/maxresdefault.jpg  or  this:   https://s-media-cache-ak0.pinimg.com/originals/29/04/34/290434956cdd220cc8d6e0b18948cf3c.jpg or this:  https://www.t-nation.com/img/photos/2013/13-775-04/Nordic-Start.jpg

Keeping your hips flat (straight line from knees through hips and shoulders) – you lower your body down slowly until you can no longer hold your weight then catch yourself in push-up position and push back up:  https://simplifaster.com/articles/wp-content/uploads/sites/5/2017/03/GHR.jpg .       You can also use a band during the exercise which provides progressively more assistance as you go lower towards floor to allow you to potentially perform the full range of the motion and come back up with the assistance of the band.    Then over time you gradually decrease the assistance of the band by user smaller and lighter bands.      This provides a good video of how you can do this by attaching a band overhead and behind you:  https://www.youtube.com/watch?v=LQm9rdzZlRk

There are also numerous machines designed for this exercise including:

http://www.roguefitness.com/floor-glute?prod_id=15905&gclid=Cj0KEQjwnazLBRDxrdGMx-Km4oQBEiQAQJ1q68P3rah0ZwofpsxOA-xSYl5_v9mtTSxSmuG5zIW1KUYaAvPW8P8HAQ

http://www.speedbottraining.com/glute-ham-machine/

http://www.gluteforce.com/

Here is a 6 week progression:

Week                   Sessions/Week                  Sets                       Reps                     Rest

1                                           1                            2                            5                            2 min.

2                                           2                            3                            5                            2 min.

3                                           2                            3                            6                            2 min.

4                                           2                            3                            7                            2 min.

5                                           3                            3                            8                            2 min.

6                                           2                            3                            9                            2 min.

What is the Best Way to Warm-Up?

There is a lot of controversy and conflicting opinions on what you should do for a warm-up for exercise.   One of the reasons is that warm-ups should vary based on the activity you are preparing for and your level of fitness.

As the name implies one of the key goals in warm-up is to literally raise the body temperature and gradually ramp up the cardiovascular system to be prepared for harder efforts.     The length of warm-up should be based on the intensity of the activity.     Low intensity activities like moderate pace walking really require no specific warm-up as you can simply ease into the activity itself as a warm-up.     For activities like competitive athletic events that involve high intensity effort the warm-up should be longer.

In the same way, you have to consider your fitness level because a warm-up for a highly fit individual may be relatively high intensity exercise for a deconditioned person.

For all warm-ups, a 1 – 5-minute period of escalating cardiovascular exercise that raises heart rate and body temperature is advisable.    For high intensity athletic events this should be extended until the athlete breaks a sweat without being fatigued.   

This literal warm-up can be done on a cardiovascular exercise machine or via dynamic bodyweight exercises like squats, lunges, planks, push-ups, etc.    

Once you raise body temperature you can include some dynamic stretching with an emphasis on movements that address key joints and muscles involved in the actual activity you are warming up for.   For example, for tennis warming up the shoulder joint and surrounding muscles is important while for cycling this is less relevant.

 A Proven Warm-up Protocol

Warm-ups for sports participation have been researched and there is one in particular protocol that is proven to reduce injuries by improving muscle strength, balance, and coordination.    This protocol is called the FIFA 11+ Program and involves doing 15 exercises.    For a complete how to guide click here:  https://www.slideshare.net/PedMenCoach/fifa-11-warmup-to-prevent-injuries 

Although this protocol was developed for soccer it can easily be modified to fit just about any competitive sport!

S-Drive/Crank Cycle Tabata Workout

The S-Drive and Crank Cycle can be used together for a fantastic HIIT Training Workout that is very simple to execute and appropriate for all ability levels!

For the S-Drive portion the exercise is sled pushes so take the belt system off and let it hang from the front of the S-Drive.   Use the sled resistance on the left side of the S-Drive to select and control resistance levels.    You can also use the parachute resistance on the right side to fine to the level of resistance.   

You will be doing a total of 8 sets of sled pushes for 20 seconds of work and 10 seconds of rest, and ideally you choose 4 different hand positions for two sets each at low to high levels so that you change the angle of load/push to create a complete lower body workout!

Sled push exercise video:  https://www.youtube.com/watch?v=wupkFtT69C0

For the upper body portion you will do 8 total sets of Crank Cycle all done standing as follows:

Single Arm Left Cranking – done standing in straddle stance with left leg forward and right leg back with right foot on ball of foot on sloped surface of rear portion of Crank Cycle.

Single Arm Right Cranking – reverse of above

Double Arm Forward Together – standing feet parallel

Left and right crank arms 180 offset – standing feet parallel

Then you flip the locking mechanism to turn the crank tower 180 and lock it down. 

    

Repeat all four of the above in the opposite direction.

For a tutorial on how to use the Crank Cycle see:  http://www.matrixlearningcenter.com/how-to-use-krankcycle/

Workout

Set up a timer for two rounds of Tabata – 20 seconds work and 10 seconds rest for 8 repetitions with a one minute break and repeat.

Start on s-drive doing a set of sled pushes

Then immediately go to Crank Cycle for set of single arm cranking as per above.

Repeat this cycle 4 times changing hand position for each set on S-Drive and changing exercise each set on Crank Cycle.

After 8 total intervals (4 on S-Drive and 4 on Crank Cycle) take a one-minute break.    During the break turn the Crank Cycle Tower 180 degrees as per above.

Repeat another 8 total intervals (4 on S-Drive and 4 on Crank Cycle).  

This workout will take 9 total minutes plus a 5-minute warm-up and cool-down for a total of 19 minutes!   You will not believe the results – perform 1 – 3 times per week with your best effort!

Superman Shoulder Press with Flat, Circular Band

Flat circular bands are a simple, but amazing tool that provides a very different loading profile than free weights or machines.   One of the best exercises with a flat, circular band is the Superman Shoulder Press.   It provides loading that matches the shoulder’s strength curve in that the more the band is stretched the heavier the load.  During the shoulder press your leverage, and hence your ability to produce force, increases as you get closer and closer to extension.

To do the Superman Press step inside the band with feet shoulder width apart or wider.   The wider your feet the more the band will stretch and the “heavier” the load that will be produced during the press.   So you are literally standing with both feet on the band which then goes up around the feet (it is circular right?).   Then holding the band with both hands at the same time “clean” the band so you are in a position to press it overhead.   The band will go down from the outside of your hands then down to the feet and also across from one hand to another.    Notice that you can adjust your hand position in or out to make it more comfortable and your hands should be holding the band at shoulder level (top of chest).

Keeping the core muscles tight and engaged press the band up AND out as you extend the arms fully overhead.  By pressing out while you press up you create space in the shoulder capsule and prevent impingement.   Many people who feel pain with a dumbbell or bar overhead press find they can get all the benefits of an overhead pressing movement WITHOUT the pain because of this.

To make the exercise more metabolic add in the lower body by doing a squat from the starting position as you hold the band at your chest level and then do a press from the standing position – basically a band thruster providing a full body exercise that really jacks the heart rate.

The other advantage of the Superman Press is that with bands you can safely move at high speed during the concentric phases to work on power – but always pause at the top and lower slowly to get the other benefit of band training – a great eccentric load!

For a good video of the movement click here:   https://resistancebandtraining.com/exercises/shoulders/shoulder-press/

What does "Grass-Fed" Meat Mean?

If you shop for the food in your family you have probably started to see the term “Grass-Fed” on more and more meat products.   You may have wondered what it means and what significance it has for human health.

To make it more confusing this term is often thrown in with other terms such as “Organic” and “Grass-Finished”.       To understand all this let’s start with talking about Grass as opposed to Grain Fed.     Cows and other Ruminants including cattle, goats, sheep, giraffes, deer, moose, and caribou to name a few have a natural diet based on what they have eaten for hundreds of thousands of years.     Their bodys' and specifically their digestive systems were shaped by evolution to eat green plants!

For thousands of years that is what they did eat, but in modern times cattle farmers learned that feeding a ruminant grains and corn will put weight on them much faster than their ancestral diet of green plants consistently mostly of grasses.      This translates to quicker time to slaughter, lower costs, and higher profits for the farmer!  Grain and corn is the metabolic equivalent of feeding cows a diet of “Twinkies” with all the consequences.      In addition, grain fed cows have a particular taste and Americans in particular have become used to it and partial to it.

Unfortunately, grain fed animals have a very different fatty acid composition than animals fed a grass diet.      Grass-fed cattle contain much higher levels of many beneficial compounds including anti-oxidants, Omega-3 Fatty Acids, Conjugated Linoleic Acid (CLA), Trans-Vaccenic Acid (TVA), Trace Minerals, and vitamins.      

The worst part is that most meat is not just grain fed it is injected with hormones and antibiotics that also speed up weight gain and the corn and grain is very low quality and heavily sprayed with pesticides so you’re eating tons of toxins when you consume meat raised this way!

Omega 3 Fatty Acids are essential fatty acids as our Omega 6 Fatty Acids meaning we must consume them and cannot manufacture them in our bodies.   We need both in a balance.     Unfortunately the American diet is way too high in Omega 6 fatty acids and this has big-time consequences to human health (see this previous blog post to understand the need for lower intake of Omega 6 Fatty Acids and Higher intake of Omega 3 Fatty Acids and how and where to get both - http://workoutanytime.blogspot.com/2016/11/omega-3-fatty-acids-and-health.html )

Anti-Oxidants are crucial for health and grass-fed meat has much higher levels of carotenoids like Beta-Carotene and others.    Carotenoids are fat-soluble meaning they tend to get stored in fats making the fat look yellow.      Yellow fat (like butter from grass-fed cows) is a sign of high nutrient density.    More carotenoids = more antioxidants and more nutrients (plus richer flavor!).  

CLA provides several key benefits including:

Improving weight loss and specifically reduces bodyfat! 

Helps increase lean mass including muscle and bone!

Potent Anti-Cancer Effects

Helps reverse atherosclerosis (hardening of arteries)

Improved digestions

Helps balance inflammation and immune function

Reduces food allergies and sensitivities.

TVA – aka Trans Vaccenic Acid is technically a trans-fatty acid, but unlike man-made transfats which are unquestionably NOT healthy – there are benefits to TVA.    Naturally occurring TVA in grass fed animal products may help lower cholesterol and LDL cholesterol in particular along with lowering triglycerides.  TVA can also be converted to CLA in your body.     Like CLA TVA seems to reduce risk factors associated with heart disease, diabetes, and obesity according to research from the University of Alberta.

Grass-Fed vs Grass Finished

Grass-Fed means that cattle ate nothing but grass and other forage (like hay or silage) for their entire lives.   This means they were never fed grain at any point. 

As the name implies Grass-Finished means the animal was fed grains but was “finished” eating grass before slaughter.    How much time eating grass vs grains and the quality of grains makes a BIG difference.      Just 90 days of grain feeding destroys all the benefits of grass feeding so knowing what the animal ate and for how long is key which is why you ideally buy beef from a farmer you know and trust!    

Alternatively buying meat that is organic AND grass-fed is by far the best option.     Just Organic means the grain fed to the animal was not sprayed with pesticides which is good, but this does not provide the many benefits of feeding the animal a grass diet as described above.

See next Month's Blog for a detailed explanation of the term "Organic" and how to interpret all those differrent lables such as "Certified Organic", "100% Organic", "All Natural", etc.

Do You Really Need to Drink Eight Glasses of Water Each Day?

Everyone knows you need 8 glasses of water each day to stay healthy right?    Wrong!   Of course, drinking water is essential and the best way to get the water you need is by drinking water (not soda, juice, or sports drinks), but it is a misconception that you need to drink 8 glasses per day and that more is always better.    

The National Academy of Sciences recently concluded that most Americans are adequately hydrated.   Direct Quote “The vast majority of healthy people adequately meet their daily hydration needs by letting thirst be their guide.”

Typically, about 80% of your total water intake comes from water and other beverages with about 20% from the food you eat.

Another associated myth is that if you wait until you are thirsty it is too late because you are already dehydrated.   For the vast majority of people your physiological thirst mechanism is triggered before you become dehydrated.

Another myth is that if your urine is yellow or deep yellow you are dehydrated.     This could indicate dehydration but urine color is also strongly affected by other factors including intake of certain vitamins and other chemicals we take in from food and drinks.

Dangers of too much water intake

There is a very real danger from excessive water intake and the number of people affected by this is growing – particularly in sports.   This may all stem from a paper published by the US Military stating that soldier should drink 64 ounces of water per hour in order to improve performance.  It was and still is widely embraced although there is not scientific support for this advice.  Even the American College of Sports Medicine recommends “…drinking ahead of thirst.”   The problem is this can be taken too far and in fact excess water impairs performance and actually can kill someone if it is excessive enough.   It is important to note that data demonstrates mild degrees of dehydration do not impair performance.

Excessive water intake coupled with exercise can result in exercise-associated hyponatremia (EAH).   EAH is also commonly referred to as “Water Intoxication.”   In EAH, the body’s cells, including those in the brain, swell with too much water, which can be fatal.    When the body has too much water relative to its salt level, the salt level in the blood drops too low which leads to significant problems.

The Right Strategy for Water Intake

The easy answer to proper hydration is to pay attention to your thirst and drink accordingly.     This applies to sports drinks as well.   Also it goes without saying that not getting enough water is not advisable.  When you do not drink enough water it puts you at a much higher risk for kidney stones and this is one of the most painful conditions there is!   Dehydration can also negatively impact cognitive function and mood.

Dehydration is more common in children and the elderly, and risks of dehydration get higher as the temperature and humidity rise.   During hot humid weather the body sweats profusely but because of the humidity sweat does not evaporate so cooling is not nearly as effective and the body just keeps sweating without much effect on body temperature.   Dehydration is also much more common in extremely cold temperatures below freezing because the air becomes extremely dry and with each breath moisture is lost.     In addition, in cold temperature the thirst mechanism can fail to kick in.     The end result is that dehydration is a very serious risk in prolonged exposure and exercise in cold environments!

So How Much Water Do You Need?

While you probably do not need 8 glasses of water per day – it probably is not going to hurt you in most cases.    Actual fluid intake and needs will vary from individual to individual depending on their size, activity level, and the amount of water present in the foods they eat each day.

However, the take home message is simple – pay attention to thirst and drink when you are thirsty and try to stick with good ole H20 rather than juice or soda.      It is what your body needs without all the extra calories!

Kneeling High to Low Chop - The Best Core Exercise You are Not Doing!

Core stability is a big buzzword in fitness, and for very good reason.     The ability to keep the core stable is essential for proper movement and prevention of injury.      Stability has three aspects related to the planes of movement:

Sagittal Plane Stability – is the ability to prevent flexion and extension of the core from the low back to the top of the head.

Front Plane Stability – is the ability to prevent lateral flexion of the core from the top of the head to the low back.

Transverse Plan Stability – is the ability to prevent rotation of the core from the top of the head to the low back

Stability is about preventing movement – not creating movement!   All muscles can act as stabilizers, movers, or absorbers, but the muscles of the core spend a lot of time preventing movement in many activities from running to walking to jumping.    This is why exercises like the plank are considered functional because the plank is about using core muscles to prevent movement of the core as opposed to exercises like a crunch which is about creating movement.

To have a strong and stable core it is important to perform stability exercises in all three planes of movement.     The plank and side plank do a great job of challenging muscles to prevent movement in the sagittal and front planes, but that leaves the Transverse Plane.    This is significant because the vast majority of injuries occur in the Transverse Plane with Frontal Plane injuries close behind.

It is also important to note that rotational movement (movement in the transverse plane) is fundamental to human movement in general and the generation of explosive force in many activities from Golf to Tennis to Boxing.

One of the best ways to develop rotational stability in the Transverse Plane is doing high to low anti-rotation chops in a half kneeling position using either resistance bands or cable resistance with a rope handle or pole attached.

Execution

The anchor point of the resistance band/location of the cable handle should be position up high.     Your body should be facing perpendicular to a line from the handle/anchor point straight down and across your body.     You should be in a half kneeling posture down on one knee (the leg closest to the cable/band should flexed with foot flat on the floor and hip and knee bent at 90 degrees.   

The other knee should be down on the floor (use a cushion or mat!) with shin and top of foot along the ground directly behind the knee.   It is important that the knee is directly under the hip.  It is also important that the spine be held straight with a straight line from top of head through the spine and hip to the knee on the ground.    Extend the spine fully and keep your spine fully elongated throughout the exercise.

Reach across the body and place both hands on the resistance band/rope spread apart with hands shoulder width apart.gripping the band/rope.

Keeping the shoulders and hips facing forward the entire time pull the rope/band directly down and across the body and pause in the bottom position making sure there is no movement to in the shoulders or hips while maintaining a fully lengthened spine.   Then slowly return to the starting position.    Form is VERY important in this exercise.

Here are two great instructional videos:

http://www.stack.com/video/3730538400001/elite-performance-with-mike-boyle-increase-core-strength-with-anti-rotation-exercises

http://www.muscleandfitness.com/workouts/abs-and-core-exercises/videos/half-kneeling-stability-chop

Squats and Anatomical Variation Among Individuals

Squatting is one of the fundamental movement patterns everyone should train, but it is very important to understand and consider the effect that individual variations in limb length and anatomical variances can have on exactly how each person can and should squat.

Everyone cannot and should not squat the same way!  Many trainers and individuals try to squat in “perfect” form with feet flat, no heel lift, feet pointing forward, with back upright and straight with butt to the grass but this is not only not possible for some people – it can actually get them hurt!

One of the biggest factors determining how an individual can squat is the relative length of their femur (upper leg bone) relative to their lower leg and upper body length.       In general, the longer the femur  and the shorter the tibia (lower leg) the more a person MUST lean their upper body forward in order to get thighs parallel to floor much less going below parallel.     This puts a TON of stress on the low back and in extreme examples trying to get to parallel is a BIG MISTAKE – swap for another exercise like a lunge or step up – nobody wins when you get hurt exercising!

To gain a really strong understanding of these concepts check out this fantastic article on this subject by Bret Contreras that includes video links to a short, but powerful video presentation on this subject using a stick model: https://bretcontreras.com/how-femur-length-effects-squat-mechanics/  .     Once you see it you will never try to force someone into a fixed squat pattern again without really thinking it through.      Also check out these videos from Tom Purvis which show this clearly in a way that is very easy to comprehend https://www.youtube.com/watch?v=Av3LO2GwpAk and   https://www.youtube.com/watch?v=KGEKRjlZKf8 

In addition to limb length differences there can be dramatic differences in the shape of the acetabulum (the hip socket), the head of the femur (ball of femur) and femoral neck angle.   The end result can mean very different squatting mechanics are required.     Here is a great article showing how these differences manifest themselves in squatting:  https://bretcontreras.com/no-two-hips-are-the-same-how-anatomical-variance-can-affect-your-range-of-motion/