What Equals a Fast Athlete, and What is "Fast"?

Thoughts from an article that I recently read…

The most commonly used bench mark and testing method for athletic speed is often the 40 yard sprint time. However, that test is not entirely specific when it comes to many athletic situations beyond actual short distance track athletes. In most situations, and with most sports, the athletes will not be called upon to perform an all-out, maximal sprint for 40 yards. Most often the athlete will need to change direction quickly, react quickly, and have a powerful and fast first step. Measuring this ability is not effectively predicted with just a 40 yard sprint time. Let’s look further into first step/reactivity and all-out speed. This discussion will be taken from a study in which 26 male rugby athletes were tested in various ways to ascertain strength and power attributes. These findings were then correlated with speed attributes.

This study used 4 different methods to assess strength and power, and used those data points to find the correlation to athletic speed. Basically, the study sought to find what attributes of an athlete equal a “fast” athlete.

The first was a series of speed tests. The tests included: First Step Speed/reactivity (5m sprint time), Acceleration (10m sprint time), and Max Speed (30m sprint time). These tests were assessed using a standard sprint timing light system.

The second test was that of maximal strength and was assessed using the 3RM back squat. The participant used a plate-loaded barbell, in the high-bar position, and performed a basic squat. Beforehand, the subject completed a basic warm up which included static stretching, and was then given as many attempts as needed to get to a maximal number; increasing in 5kg increments each time.

Thirdly, Power and Reactivity was tested utilizing 3 different jump methods. All of the jumps were performed on a Kinematic Measurement System (KMS/ Electronic contact mat). The first jump method was the Squat Jump. A bar of standard weight was placed on the test subjects back in the high-bar position while the athlete was standing on the contact mat. The subject was asked to jump as high as possible with the weight upon his back. The second jump method was the Counter Movement Jump. The subject stood on the contact mat with hands on the hips. The subject then jumped as high as possible without letting the hands leave the hips. The third jump method was the Drop Jump. The participant was asked to step off of a 40cm box onto the contact mat and explosively and quickly jump as high as possible upon landing on the mat.

The fourth and final assessment used a Biodex machine and measured the isokinetic leg strength of the participants. The procedure involved a warm up which again included static stretching. The subjects were then put through a series of assessments on the machine to determine isokinetic torque measurements of knee flexors and extensors.
Upon conclusion of the testing, the sample group was split into the 13 fastest (had fastest 5m sprint times) and 13 slowest (had slowest 5m sprint times). From this point, the numbers from the various tests were compiled and then correlated with each other to assess the causality of the faster and slower athletes.

Right off the bat it was obvious that the Biodex test had very low correlation to speed. This is largely due to the fact that the Biodex is measuring flexion and extension strength at the knee. Most of the running strength comes from the hip region.

The maximal strength test (3RM squat) did not correlate with the jump assessments or the speed assessments, however it did correlate well with the isokinetic measurements; namely, the hamstring/knee flexor strength findings (Biodex). This is not surprising because both of these tests are indicators of hamstring strength; they test the same attribute. Hence, they should correlate to a degree. But the fact that they correlate with each other serves no purpose for what we’re looking for here… It did not correlate with speed.

Ultimately it was found that the strongest correlates to sprint performance were the 3 jump tests. Therefore, they strongly correlated with all 3 of the sprint tests (5m, 10, 30m tests). It should be noted that these were the only tests that correlated with ALL the speed assessments. From start speed (5m sprint), to carrying speed (30m sprint), they had relevance.

What I found most interesting was that the 5m sprint/reactivity test was NOT a close correlate to 30m full speed times. This would indicate that start speed or “first step speed” is an athletic attribute in itself. It cannot be put in the same category as all out speed. To explain further, many people think that a quick person is one that can perform a 40 yard dash quickly. However, this is not an indicator of that athlete’s overall speed. While the athlete with absolute speed may cover 40 yards quicker, the quick stepping athlete can feasibly react to an event quicker, initiate counter-movement sooner, or out maneuver more effectively. This finding is, in my opinion, one of the most important of this study.

The author set out to show the importance of not only more specificity in speed testing, but to also show the significance of first step/reactivity speed in field and court sports (hence the use of field athletes like rugby players). The author was successful in proving that it is a standalone attribute with great significance. What’s the point? Studies of this sort can provide better insight to the field of athletic Strength and Conditioning. A fast field or court athlete does not have to be, nor should he be, trained and tested as a short distance sprinter; as is often the misconception.

(I want to clarify, however, I'm not postulating that squats or hamstring development are pointless for speed development. Remember that heavy back-squats develop the central nervervous system, and the study did find that jumps correlated well with reactivity (as they are in themselves a reactive movement). Squats can increase rate-force production by improving the efficiency of central nervous system firing. Squats can definitely increase jump strength. Though this study did not find a heavy correlation between squat strength and running speed, I do firmly believe that they serve a role in creating a faster athlete by helping the athlete build a strong central nervous system base. )

• Cronin, J. B., & Hansen, K. T. (2005). Strength and power predictor of sports speed. Informally published manuscript, New Zealand Institute of Sport and Recreation Research, Auckland, New Zealand.

Here watch this....

I would like to say that it surprises me at some of the things that are posted on media outlets about performing exercises, but lately nothing surprises me. I was watching a video the other day and was quite amused and appalled at the exercise being performed and the "coach" giving encouragement for the improper technique while weight is loaded on the bar. The aforementioned exercise is a power pull, at least that is what the title states. Scary took the words right out of my mouth when he said it looked like a weighted jumping jack.

In the video the athlete sets up with the shoulders in front of the bar, his weight is not shifted to his heels, and the back is not set. The athlete then proceeds to dip his shoulders on the start and jerk the bar off the ground, pull the bar as high as he can then lean into the weight to give the illusion that the bar is traveling higher. As the athlete pulls he splits his feet as doing a jumping jack and then moves them back in same motion to drop the weight. Three reps are performed and with each rep the technique breaks down even more, if that is even possible.

What really gets under my skin, besides the fact that this was actually put online, is that technique was obviously not a priority. From the set up to the execution of the exercise, not once was there a cue to remind the athlete of technique, "get that pull, get that pull" is the only thing said to the athlete. No technique and no reiteration of proper form.

All I see here is an athlete that will more than likely be on the road to a having an injury. It might not happen right away but if he stays with how he is performing this exercise, than it will be inevitable that at some point something will happen. Technique needs to be stressed and the intensity lowered. It really is that simple, if an athlete can't perform a lift properly than lower the weight and have him perform the exercise until proper form is achieved. The "coach" needs to see that and not worry about posting a video on something just to put something online.

So to sum it up, technique technique technique...plain and simple. If proper technique is not taught and coached consistently and continuously before the bar is loaded and then, during the progression, you are setting your athlete up for eventual injury.

Getting the Most From Your Time/Training

Recently, I have been switching up my normal training habits with great success. My standard training protocol was to perform one main lift. It may have been squat, bench, deadlift, or hang cleans. That was followed by an assistance exercise that related to the main lift for the day. For example, on squat days I would follow up with good mornings and some back work. This was mainly due to not having a solid hour where I could do my workout. The training was interrupted by work-related tasks, either a coach needed me to do something, or I had 30 minutes before one of my teams came in and I knew I wouldn't have time to do everything I know I should do. The last 6 weeks I have made some changes that have helped my time management and my training go much better. Here is a list of changes I have made:

Begin with a thorough warm-up and speed training

I have been short changing my workouts by not doing a good warm-up. But now, in the limited time I have, I make sure I do a good warm-up. This is a dynamic warm-up that encompasses the entire body. It gets my heart rate up and addresses imbalances in the body and increases joint mobility. If anything, I know this has made me feel better on a consistent basis. After my warm-up, I do short sprints or agility work to really get my nervous system fired up and it helps my mind prepare for the task at hand.

Perform core lift with an activation exercise

I have been doing squats coupled with box jumps, bench press with med ball throws, and hang cleans with depth jumps. This allows me to work in a lower volume set/rep scheme and maximize the effectiveness of the lift. The heavy weight of the core lift recruits more motor units. Then immediately going to a plyometric/ballistic movement in relatively the same pattern, increases speed of contraction. After one set, I have recruited a large number of motor units and increased the rate at which they are recruited. After four sets, I have tapped deeper into my musculoskeletal system and nervous system than if I were to have done straight sets of just the core exercise. In the end, the stimulus I have put my body through has resulted in more Type II fiber work, increased efficiency of the nervous system, and a more sport-applicable task has occurred, increasing transference of training.

Usually at this point in my training, I have run out of time and must end the current session. That is fine though, because I have addressed imbalances in my body, increased joint mobility, and performed weight-bearing exercises that increase GH and Testosterone production, bone density, and some level of conditioning by pairing exercises, doing sprints, and performing a continuous movement warm-up. I now have two options: do my accessory work at the end of the day or the following day. This mainly depends on how much time I have left in the day and what tomorrow looks like. Either way, these are the other changes I have made that helped.

Unilateral strength effort movements related to the core exercise

These exercises address the weaknesses in the kinetic chain, increase joint stability, and emphasize target muscle groups to assist the core lift. I begin the next training session with these lifts because they get my heart rate elevated again and increases number of motor units recruited, which will make the most out of my high volume assistance work that I will be doing after the unilateral SE work. For example, following squats I do lateral lunges, cleans: single-leg RDLs, and bench press: single-arm dumbbell rows. The lateral lunges help me to concentrate on pushing me knees apart as I squat, as well as increasing the number of planes that I train in, which helps knee and hip health, while also training to be more athletic. The back training with bench works the antagonistic muscle group to increase stabilization of the shoulder joint during pressing movements, and strengthens posture muscles related to all lifts.

High volume single-joint assistance work

I finish the training session with high-rep sets of exercises that relate to the core lift. For example, squats: TKEs, cleans: power-shrugs or heavy glute bridges, and bench: tricep extension of some sort. I know power-shrugs are not single joint exercises, but I do them to train in the same movement pattern as the clean and focus on hip extension (and I love shrugs). With bench press, I do tricep extensions. I usually prefer bands because they can be manipulated to train in different planes and body positions you cannot do with free-weights. From time to time I do close grip bench or plate presses. Again, not a single-joint movement, but the prime mover in the exercise is the triceps.

The final thing I have changed in my training for the better is weighted or stabilizing core (abs) work. The exercises I have been performing recently with much success are : wrestler's twist, Paloff press, and walking planks. They all involve the shoulders, which is good for me because I have a winged left scapula I am trying to fix. The wrestler's twist involves placing a barbell with one end in a corner and weight on the other end. While grabbing the weighted end, violently rip the weight from one hip to the other in an arcing motion, as if trying to body-slam someone. I perform the Paloff press in a squat stance with bands attached to a bar, perpendicular to the plane I am pressing in. As I press the band away from the body, the trunk must resist rotation. The walking planks begin on your hands in a push up position. Slowly walk the feet backwards until your body is in a straight line, and your nose is as close to the ground as it can go, without the body completely collapsing.

One thing I highly emphasize, but did not address as a change, is multi-planar movements. I have been doing this all along, which is why it is not a change. Make sure you are pressing and pulling in all planes, as well as lunging/squatting/jumping in all planes as well. It creates a better athlete, but also a better body because we were meant to move, not just look pretty and lift heavy weight.

Cybernetic Periodization

I was reading a Mike Robertson blog the other day about Cybernetic Periodization and made me think about how I could apply this to my workouts or a group of athletes.  Cybernetic Periodization is not something in the terminator; it’s a termed coined by Mel Siff author of “Supertraining” and I will attempt to explain in detail in this post. 

When designing a regular workout plan for your busy inconsistent schedule it’s hard to stick to the numbers and designated days of the week. What I mean by this is your CNS in a perfect world would reset every 72 hours like clockwork with a perfect periodized routine and adequate recovery.  With a lack of recovery, deficient amount of caloric intake, and High CNS and Muscle Skeletal fatigue prior to your next workout, limits you to be fully prepared for your perfect program.   My solution to this problem would be following a Cybernetic Periodization schedule. 

So what is Cybernetic Periodization?  It basically is training on how you feel for day of your prescribed workout. This is when auto regulate your training routine through relative programming.  The basic format for the workout stays the same with high/low/med/low/high with a selection of exercises based on the amount of motor units recruited.  What will change in the routine is the volume, intensity, and exercise selection based on the RPE for the day.  RPE stands for Rate of Perceived Exertion, which means how much effort am I able to put into the workout for the day.  The RPE scale should range from 1-10; 1 being the worst feeling and 10 feeling great.  Then you take this scale and determine your variables from all the qualities in the chart below.  The first two qualities to look at are your volume and intensity ranges, which I refer to the prelipin table.  Within the prelipin table you have a relative intensity range of 10% to follow and a total volume range within that intensity range.  So if you are working at 80% intensity and your RPE for the day is a 5 your volume selection for the day would be in the middle of what is recommended.  This is based off your core lift for the day.

Example:

RPE	Exercise	Intensity	Volume
1-10	Back Squat	80%	10-20

Following the primary mover for the day you select 2 to 4 accessory exercises that compliment the core lift.  This is where you would get your high volume from for your training and keep the intensity low.  When it comes to an Olympic Movement, Squat, Deadlift, or Single Response Plyometrics the exercise can only be trained every 72 hours.  So the question is, “What do I do in between those days?”  Bench, OH Press, Cardio/Tempo Runs, Upper Pulls.  If you feel that you have hit the wall don’t hesitate to take a recovery day with some regeneration work mixed in.  This program should be followed on a 7-9 day cycle, coming back to the primary exercise.

Example:

	Core Exercise	Accessory 1	Accessory 2	Accessory 3	Accessory 4
Day 1	Clean	Jerk	Deadlift	Shrugs	Leg Curls
Day 2	Bench Press	Bent Over Rows	Incline Press	Pull Ups	Triceps
Day 3	Tempo Run/Regeneration
Day 4	Squat	Box Jumps	Step Ups	Leg Ext.	Glut/Bridge
Day 5	OH Press	Upright Rows	Seated Rows	Push Ups	Biceps
Day 6	Tempo Run
Day 7	Recovery/Regeneration

	Core Exercise	Accessory 1		Accessory 2			Accessory 3		Accessory 4
Day 1	Clean	Jerk		Deadlift			Shrugs		Leg Curls
Day 2	Bench Press	Bent Over Rows		Incline Press			Pull Ups		Triceps
Day 3	Tempo Run/ Regeneration
Day 4	Squat	Box Jumps		Step Ups			Leg Ext.		Glut/Bridge
Day 5	OH Press	Upright Rows		Seated Rows			Push Ups		Biceps
Day 6	Tempo Run/ Regeneration
Day 7	Deadlift		SL Movement		Pull Up	DB Press		3 Way Delt
Day 8	Medicine Ball Circuit
Day 9	Tempo Run/Regenerate

So when it come to auto regulating your workouts, you must be able to push the envelope on days your feel great while going at the higher end of your relative intensity and volume range, and  back off on days you feel down.  You soon will see that you are able to get more out of your workouts and see better results in the gym. 

P.S. Don’t forget these fundamental principles when following a Cybernetic Periodized Program.

·         Volume Range

·         Intensity Range

·         Exercise Range

·         Exercise Selection

·         Training Frequency

Why I Don't Go to the Rec Center

1. This guy. (see picture above)
2. Bad Technique - it makes me want to vomit because of how it looks, and what is about to happen to that joint.
3. Bench and Bi's - the one time I went to the Rec, the first 7 guys I saw walk in there did either bench or bicep work as soon as they walked in.
4. Wife Beaters/Cut-Offs - every frat boy wears a wife beater or cut-off to workout. Don't wear one unless you bench at least 1.5 times your body weight or can squat at least twice your body weight. PS - nobody cares about your skinny arms.
5. Skinny Legs - DO A FREAKING SQUAT FOR ONCE IN YOUR LIFE!
6. Screaming with Light Weight on the Bar - enough said.
7. Spotting on Accessory Lifts - if you can't lift it, put it down.
8. No You Can't Work In, You Are Weak! - I'm not going to slow my session down to take weight off so you can get back to flexing your calves in the mirror.
9. Gloves - put the lotion away and get some man-hands. Your hands may be soft, but I'll still kick your butt and steal your girlfriend.
10. Curls in the Squat Rack - its called a "Squat Rack" for a reason. Figure it out.
11. "Trainers" telling me I'm doing something wrong - DO YOU KNOW WHO I AM?! Before you say anything, prepare to shut up. Don't get me started.
12. No I will not help you rub tanning lotion on.
13. Who wears hair gel to workout?
14. If you have skinny legs, do something about it, other than wear sweat pants.
15. You don't need a pre-workout shake to do that weak workout.
16. I'm not working out. I'm training.
17. No I'm not on Steroids.
18. No I will not write you a program.
19. Squatting past parallel will not hurt my knees.
20. People taking 10 minutes between sets to parade around and look at girls.
21. Stop flexing, you are about to pull something.

The Youth Sport Conundrum

As a coach and parent I always have people assume that I’m going to push my daughter to participate in sports. Although I won’t allow her to be the next XBOX or Wii junkie, nothing could really be further from the truth. Personally I’m really not a fan of most youth sports for a number of reasons, some of which I will expound on below as most of these are rarely emphasized.

Physical Development- A tremendous amount of physical development can be gained as a result of participating in sports. It should be the goal of the coach to properly progress and develop the athlete in a way that will benefit the athlete for current participation as well as encouraging life-long fitness.

Psychological Development- Too often, athletic participation is looked at as having a negative affect on an athlete’s psychological development. However, when a coach provides the proper learning environment it is a great way to teach someone how to compete and how to accept the outcomes of their participation, whether it is winning or losing. Promoting the benefits of the athletic experience rather than just winning or losing is the most important issue that should be stressed because winning should be a by-product of the experience and losing should be viewed as a way to address change, learn and personal growth.

Social Development- Sports provide coaches the opportunity to teach honesty, self respect, sportsmanship, acceptance of winning and or losing as well as accountability for one’s actions. All of these must be addressed in sports to allow for the overall development of the participant as an athlete and as a person.
Relationships- The coach-athlete relationship must be professional and one of a mentor at all times with both parties understanding that there are limits to this relationship. It is extremely important that the coach exhibits a professional relationship at all times and with all who may be present before, during and after an athletic performance. The coach should respect officials as well as opponents players and coaches.

Ethics-Because of their role as a coach and the influence that they have over those that they come in contact with, anyone who is a coach is a role model for athletes and represents all those in the profession. A coach must strive to represent the profession as well as possible through their behavior, dress and relationships that they have with others. It is extremely important to realize the influence, authority and responsibility that a coach has on others and therefore, their personal life should also be held to high standards. A coach also has the responsibility to maintain safe practice and competitive environments by making sure equipment is safe, properly fit and legally maintained.

Professional Development-To be a successful coach one must strive to attain the highest amount of knowledge possible. This is extremely important for the growth and development of not only the coach but also the athletes as you can better educate them on why they are performing something. With a broad knowledge base, a coach will have a better understanding of the demands, techniques and skills of the activity that they are coaching/training. This in turn will help in the development of more appropriate/sound programs for the athletes.

I think if more coaches and parents would stress these six items they would provide a much more beneficial environment for their child and teams they are associated with. Who knows, it may even help prevent some of the parent/coach/official fights that have been documented in youth sports. There might not be as many 12 year olds getting OPTIONAL Tommy John’s surgery so they can try to fulfill their parents hope of him being the next big league phenomenon. You might see a drop in the number of youths that get burnt out and stop playing sports all together. Here’s a link to Dr. Chris Stankovich’s that youth sports coaches and parents might want to check out. http://blog.drstankovich.com/blog/tag/youth-sports/

Fighting The Fear....

The fear of getting back on the playing surface after sustaining a serious injury can be a daunting task. As a former Division 1 Collegiate baseball player that sustained a major knee injury that required two surgeries and 16 months of rehabilitative strength training just to get back to practicing again, I understand the demons faced just to get back onto the field.

Overcoming those demons were the toughest part of getting back on the field. The thought of my injury lingered in my head. The simple act of running to first (which was how my injury occurred), was a mountain that I had to get over. For the longest time I would slow down when approaching the bag and it really took a toll on me. My strength was back to where it should be, but the fear of my injury really hindered me from being the player I was before it occurred. It took a little time, but I eventually came to grips with the fact that if I ever wanted to play baseball again I would have to face those demons and push through the mental block. Once I did, my "game" came back and I was out there having fun playing the sport that I love without fear.

For athletes today that have sustained a major injury, it might not be as easy as just regaining the strength and conditioning to get you back on the field. If you do have the mental issue of getting back out there you will have to find the will to persevere.

Fight that fear and get back to playing the sport that you love!

The other night I was having some trouble sleeping because of the amount of things I had running through my mind. These thoughts varied anywhere from work (programming/planning my sports, our football road trip the next day and my interns handling their responsibilities for me when I was gone) to thinking about my little girl and her upcoming soccer game that I was going to miss. It was at this time, about 1:30 a.m., I started to think about perspective and the role it plays in both our personal and professional lives.

The world is filled with a wide variety of very interesting individuals whose outlook on everything is as extreme as their personalities. However, the perspective that people have in their personal and professional lives will help determine how successful they are in both. Too often people allow what is or has happened in one aspect of their lives to affect the other, be it positive or negative. The problem with this is that people allow themselves to go from one end of the emotional spectrum to the other with very little time spent in the middle where they can be the most productive and therefore successful.

When people are dissatisfied with their job they will often do just enough for them to get by and not get fired, if you’ve ever seen Office Space you’ll know exactly what I’m talking about. This is true with both athletes and coaches. The problem with this type of attitude is that it has a snowball effect on both their personal and professional lives as they will often get passed over for promotions, raises, other jobs, playing time and other accolades related to your team.

Similar to life, sports are filled with obstacles and the perspective that one has will determine their success more times than talent or athletic ability. If you are a coach, what are you doing to improve? Are you reading something every day that pertains to your work? Are you continuing your education, be it through certification, advanced degree or clinics and seminars? Are you being the best you can for your family, community, co-workers and athletes? As an athlete what are you doing to make your team and coincidently yourself better? Are you doing the small things like watching film, getting treatment, going to class, lifting and whatever your coaches ask of you? Realize that your attitude is contagious but is yours worth catching?

Bones: Responses to Training

Bones provide the structure onto which soft tissue is built, they provide protection for internal organs, as well as provide a system of levers that allow for movement by way of muscular contraction. Much like muscles, bones undergo changes and improvements when a training stimulus is introduced, namely: impact and weight bearing exercises.

Though there are many functions and mechanisms taking place within the bones, I want to focus on the two main things that are happening within the bones when training occurs. First is bone hypertrophy due to training, and second is bone density improvement due to training.

The periosteum, a soft membrane covering the outside of bones, is responsible for building new outer layers of bone onto the existing bone. It essentially builds concentric layers of new bone, and this building is more rapid when the bones are being regularly stressed by way of impact or weight bearing exercises. It should be noted, however, that bone hypertrophy is very minuscule even when training is introduced.

The second and most prominent mechanism of bone response to training is density improvements. There are two types of specialized cells within the bones: Osteoblasts and Osteoclasts. Osteoblasts are responsible for building new bone while Osteoclasts reabsorb bone tissue. When introduced to impact and/or weight bearing training, Osteoblast activity increases while Osteoclast activity decreases. This increased activity results in greater bone density. Conversely, when an individual is sedentary, the opposite occurs. Osteoclast activity increases while Osteoblast activity decreases, effectively causing bone wasting.

Why is this important? Who doesn't want stronger bones!? This is especially important for the performance athlete within impact/contact sports. Having greater bone densities makes the athlete less prone to bone breaks and stress fractures. Even the non-contact or non-weight bearing athlete, such as cross country runners, can benefit (Cross country runners can often suffer from stress fractures that occur due to the continuous and repetitive striking of the ground during long distance runs). Having these improved bone densities also helps the average individual avoid bone wasting which can lead to osteoporosis and stress fractures.

Moral of the story: Lift heavy, run, jump, and get active!

The Latest Jag Power Quarterly

 

https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid=1J0xwUC0qLXqOYHrDLO7KhZdNArYcHajwuv-8hw94GzSjGf6FmNxZouGMKy_n&hl=en

Biomechanical Analysis of the Back Squat

Purpose

The purpose of the back squat is to increase strength in the hip and knee joints. The muscle groups involved are the plantar flexors (soleous and gastroc), knee extensors (quadriceps), hip extensors (glutes and hamstrings), and the trunk extensors (erector spinae).

Variations

There are two main variations of the barbell back squat, Olympic (high bar placement) and powerlifting (low bar placement). The Olympic, or high bar, squat requires a narrow stance, bar placed on top of the trapezius muscles, and forces a forward shin angle, emphasizing the quadriceps. The powerlifting, or low bar, squat has a wide stance, the bar resting across the back over the rhomboids and rear deltoids, which emphasizes the hips and low back. Below are pictures showing joint angles and bar placement:

Olympic (High Bar)

Powerlifting (Low Bar)

Below are a summary of the differences in the two types of back squat:

High Bar

• Greater knee flexion increases work done by knee extensors (quadriceps)
• Decreases trunk extensors (erector spinae) and hip extensors (hamstring) work

Low Bar

• Greater hip flexion increases work done by trunk extensors (erector spinae) and hip extensors (hamstrings)

Technique

For Both

• Tight core
• Tight upper back
• Unlock the hips before knees
• Chest erect

For Low Bar

• Sit back so that hips are at 45 degree angle at "bottom" postion (thigh parallel to ground)
• Shins are perpendicular to the ground

For High Bar

• Sit straight down over heels
• Shins slightly forward with knees no further forward than toes
• Hips are lower than knees in the "bottom" position

Common Mistakes

• Knees fold in (valgus stress)
• Upper back separates (poor upper back strength and trunk extensor strength)
• Not squatting to, or below parallel, shows signs of poor glute and hamstring strength

Application

High Bar Squat

• Good for quad and core development
• Applicable for sprinters (drive phase)

Low Bar Squat

• Good for eccentric loading of the hamstrings and low back development
• Important for football and other contact sports
• Many sports start in similar to "bottom" position of low bar squat