UNDERSTANDING FORCES Written by Rick Danison
UNDERSTANDING FORCES
Written by Rick Danison
Understanding forces
The reference to force in this text is going to focus on force that is not a byproduct of strength that couples with acceleration/velocity, rather how mechanical forces are placed upon the body during certain exercises. As we know training can be very beneficial to anyone’s fitness or athletic goals, but understanding some of the ways in which these exercises negatively affect the body can aid in decision making in programming as well as make it easier for us as professionals to accommodate athletes and work around certain injuries.
Shear forces:
The easiest analogy I can think of to describe shearing force is to think as if you are widdling a piece of wood, or trying to fashion a spear. In essence you are shearing of the top layer of the object in an angular motion. There are certain exercises that may or may not be a part of your program that create these shearing forces. If these exercises are performed correctly we can minimize the negative effects of these forces or keep them under control so to speak. The following are some (not all) popular exercises that produce shear force:
Good Mornings: think about the way this exercise fires up your erectors and low back. This exercise is a staple in nearly every competitive power lifters training program and may be a necessary evil to accomplish a good power squat total. Things to keep in mind; if the athlete has a predisposition to low back injury (heredity, previous injury, anterior pelvic tilt, irregular lordotic curve etc.) If you are using this exercise to create strength in the lumbar erectors and hamstrings it is by no means a terrible exercise, just a little more risky than other exercises.
Adjustments to this exercise: try an RDL, almost the same movement biomechanically, in most instances it allows for a greater load, and cuts the shearing forces down drastically. Still have problems? Try 2 for 1 approach, hit the hamstring curl hard, focus on the eccentric part of the rep, you will get more actual hamstring stimulation according to EMG and nearly no shearing force placed upon the back. We can then couple the curls with a low back variation, 45 degree hypers, prone supermans, glute ham back extension, or even just try glute hams, your body is at a much more disadvantaged position, and the load can never be as high as what an RDL, or Good Morning can be. Load is not always everything (sounds foreign to even say) but fact is overload of muscle/muscles, overcoming stress, working the muscle maximally, and adapting a muscle is the most important aspect. I can train my posterior chain extremely hard by holding a 45 pound plate on a glute ham machine and be fried.
Leg Extension: Similar to the good morning, where the load is placed on the distal end of my extremity in relation to the center point of my lever (knee joint). This load placement dictates a high level of shear force. This too is a very popular exercise, and again is a great exercise, we just have to be careful of previous injury and predispositions before throwing these exercises into our programs. For example, post ACL surgery or acute ACL injuries are probably not good candidates to have on this exercise. The leg extension, actually places more shearing force on the ACL than a squat. Also this exercise places more shearing force on the patellar tendon than a parallel squat.
Adjustments to this exercise; This exercise targets the VMO in a large capacity (huge in promoting knee stability) so an adjustment will be a bit of a downgrade if this is why you are doing this exercise as opposed to simply wanting to address training certain heads of the quadriceps. A good leg press hits the VMO, because a good leg press should be equipped to provide accommodating resistance. In contrast to being stationary, pushing a sled from the backpedal position focusing on rolling from toe to heel and getting full extension at the knee will hit the VMO also. With the leg extension being a popular staple in many programs, I prefer to keep the volume fairly low, 1-2 max sets of 8-10 in my programming, of course focusing on full extension, a good pause and controlled eccentric return.
Compressive forces:
Think of stepping on a tomato. I would venture to say the first exercise that comes to mind is the Back Squat (which I love). The Squat is viewed by many strength and conditioning professionals as the king of all exercises, in part to the fact that you can hit every muscle under the bar in the squat directly or indirectly. The squat elicits the highest GH response from the endocrine system due to the axial loading that is occurring under moderate to heavy loads respectively. Axial Loading comes from any load that puts pressure vertically over the spine, femur, tibia and on down.
I know most of us probably can’t think of a weekly training regimen without squat in there at least once or twice, but sometimes you are gonna have to adjust. Think of it this way. In athletics you are always going to have that athlete who has ridiculously long femurs, by nature often is coupled with tight Achilles. Think of it this way, you may have 8 weeks to get this kid jacked and he/she can’t squat any considerable weight without form breaking down. Is he/she weak? Is he/she not trying hard? No, they are not biomechanically well equipped. In this example of the long femur tight Achilles athlete they are not able to achieve at least a 90 degree joint angle at the knee, which most would simple say they can’t squat deep. Under these terms when the athlete attempts to squat to depth the exercise turns into a mix between a good morning and a Squat, which I like to call a bad afternoon. When the athlete demonstrates this improper technique and inability, you then are compressing a shearing force and compounding the issue further. Perception is reality in athletics, if your team looks jacked then people think your program is on point, regardless of the how genetically gifted the athletes are.
Adjustments to this exercise; other than putting the athlete in the widest sumo stance ever: Be smart and check your ego, there are, believe it or not other ways to get your legs and hips strong. Remember in most given collegiate venues an offseason is generally 6-8 weeks. This genetically predisposed athlete is not equipped to effectively complete the exercise, and the coach as well as the athlete is chasing GAINS in hopes to translate to their respective sport. A common solution could be to again combine exercises to address major targeted muscles of the squat. Simple example to substitute, leg press hard, hit reverse hypers, glute hams, and work your adductors and I’m not sure what you are missing? I can progress up to 20lbs a week on the leg press especially in the first microcycle of the year(offseason). By doing these modifications, when your given offseason has come to fruition you have concrete evidence of substantial strength gains made in the same muscle groups that the squat targets.
Torque/Torsion forces:
Think Torque Wrench, you are using a tool to place load on something in a twisting, or rotational pattern. Think about what happens to your body in an exercise that has near maximal load in a rotational fashion. Examples of this exercise: rotary torso machines, land mine twists(certain variations) not bad piece of equipment but, the most immanent concern is the utilization of the equipment or how the exercise is being coached. The aforementioned exercises could be a great way to hit most if not all of the abdominal muscles involved in rotating the torso, but there has to be particular attention paid to how the athlete performs a rep. You have to have your core set before you initiate the rotation, inhale, “set” your midsection by flexing, move without any jerking and keep the load controlled. If I do not set my core and do a relaxed jerking rep, I am significantly increasing the chances of lumbar spine (disc) Injury. The lumbar spine is not made for mobility; the closer you get to your belt line or butt, the less mobility is intended for the spine, by design. Other examples; Not the most conventional example, but think of how we teach the bench press. Tuck the elbows on the way down, while ripping the bar apart, out of the bottom, stay tight but really flare or flex the lats, and the elbows always flare out away from the ribcage as we press up. So In doing so, I am experiencing compressive forces in the AC joint, torque forces around the GH fossa,capsule, or shoulder girdle, while placing sheering forces around the elbow. The body is a kinetic chain and several considerations need to be applied across a wide scope of individuals.
Conclusion:
Accommodating around your program is not always the easiest thing to do, yet these adaptations may prove to be necessary to achieve optimal results. I personally like and utilize most of these exercises. I will always try the squat and teach the squat intensely for several sessions in a row before fully committing to making adjustments. In the case of high stakes athletics myself among others do not have the ability or justifications to let gains go by the wayside. The bottom line. As professionals, we must all understand the complexity of the human anatomy, how certain exercises coincide with the biomechanical limitations given, and what to do when an exercise is not the best choice for an athlete. If we have too much of an ego and put our exercise selection in front of our athletes physical well-being, we then are doing the athlete a disservice, and potentially leading to injury. The indoctrination of strength and conditioning programs come with a variety of challenges, and being able to recognize risk and reward when it comes to exercise selection and overall programming should stay in the forefront when addressing the training of athletes.
• Rick Danison is in his 11th year at Indiana and his fifth as director of athletic performance/Wilkinson Performance Center.
• Worked with over 100 All-Americans, eight national champions, 17 Big Ten champions (1 team), 15 NFL draftees (6 in the first 3 rounds),12 Big Ten record holders, 10 NCAA record holders, five Big Ten Athletes of the Year, four National Athletes of the Year, two Regional Athletes of the Year, an Olympic gold and bronze medalist, and a Bowerman award winner.
• A former all-conference football player and team captain at Ohio Northern University, where he earned a B.A. in exercise physiology, health and physical education.
• Served as a strength and conditioning assistant with the Cincinnati Bengals from 2008-09.
• In 2009, Danison worked as an NFL Combine performance specialist with Ignition Athletic Performance Group. The program was ranked among the Top 10 Combine training programs in the country.
• Completed his graduate work in exercise science and coaching education from Ohio University.
• Rick and his wife, Michelle, reside in Spencer with their daughter, Kynnlee (9) and son, Coy (7).