This article reviews another group of dangerous exercises, which at the same time may be the most effective. It is the technique (speed, range and trajectory) that decides about the safety, as well as individual conditions (such as proportions of the limbs, the existence of contractures) and used load. Each exercise can be harmful as well as beneficial for increasing strength and muscle mass.
You should definitely read:Physical destruction: Exercises that will wreck your body - Part 1
Exercise: leg extensions on a machine
This artificial movement imposes large load on the knee joint. Rectification is an example of an exercises belonging to the group of an open kinematic chain. Contrary to the common belief, overload to the knee while straightening legs when sitting on a machine is greater than during the full barbell squat (ATG = ass to grass). Why? In a study of 1996 it was shown that during straightening legs while sitting the load on the anterior cruciate ligament occurred in a wide range of movement (from 40 degree to full extension of the leg). The compressive force acting on the knee joint during the straightening of the legs while sitting was 4598 +/- 2546 N (the highest at about 90 degrees bend).
For the sake of comparison: the greatest strain on the joints of the knee during the squat occurs at 91 degree flexion of the knee (where according to most "experts" a barbell squat should end) - and is 6139 +/- 1708 N. If you limit the range of motion in the squat exercise in the finish = when the load of the knee is the largest, then the protective effect of ligaments (ACL, PCL, MCL, LCL) is the smallest. Conclusion? If your mobility allows it, you do not have contractures, your back is straight, you have the proper proportions of the trunk and lower limbs, you don't have damaged knees - perform full squats. Evidence? Cross-sectional studies conducted on thousands of powerlifters and weightlifters where minimal traumatism related to the performance of the back squat was demonstrated (including "Injuries and overuse syndromes in powerlifting" of 2011 and "Retrospective injury epidemiology of one hundred they Oceania competitive power lifters: the effects of age, body mass, competitive standard, and gender "- 2006). Among others it has been proved that knee injuries were the rarest injuries in professional powerlifters (9%). Damage to the shoulder (36%), the lower part of the spine (24%) and the elbow (11%) dominated in the study. It should be added that powerlifters often operate with workloads over three times their body weight in squats (a competitor weighs 100 kgs - he squats with 300 kgs) and more than twice the weight in the bench press (100 kg athlete pressed 200-250 kg). Elite athletes are able to lift even more than 400 kgs in the deadlift and over 400 kgs in the squat. If with such gigantic weights there is no "explosion of knee," what risk is there for an amateur performing squat with a weight less than twice his body weight?
In addition, we know that squats stimulate the growth of a number of additional muscles (back of the thighs, buttocks, abdomen: rectus and deep layers, spine extensors), and legs straightening is an isolated exercise of minimal impact. As for the increase in thigh muscle, straightening legs on a machine is also a bad choice: limited range of motion makes the key muscles remain untrained (for example VMO or vastus medialis). The same applies to the performance of non-full range squats.
Conclusions? If you want to have poor thigh muscles, continue with partial squats and using machines for leg extensions.
Exercise: dumbbell flies
A very good exercise that stretches the muscles of the chest, but... provided that you limit the tempo, applied weight and range of motion. Often do I see young people struggling with too heavy weights and using the maximum range of motion. This is a highway to a chest injury (tear, strain), overstrain of the elbow and the shoulder joint. Flies do not have to replace or simulate a bench press, there has to be a ballistic movement. The pace should be very slow, and the weight under total control. You can not perform flies? Focus on other exercises.
Exercise: the neck (guillotine) press
A similar kind of pressing associates with a huge risk for you shoulder joints. It forces local overload due to the unnatural movement. If you are determined to perform "guillotine", remember it can lead to long-term injury. The name itself indicates that if as a result of fatigue the barbell lands on your neck, it can end up being very sad for you. Do you want to expand your upper chest? Do not try to leave the barbell on your neck while lying on a horizontal bench only use different types of bench press and incline flies: head up (preferably with dumbbells). It is a safe alternative.
Exercise: very wide grip bench press
Too wide grip is a reliable way to excessive load on the shoulder joint (rotator cuff). Add it to your lack of slightly risen sternum, no flexed shoulders and you have a recipe for problems with shoulders. Wide grip allows for greater work of the chest, reducing the role of the triceps... but the cost may be too high. Leave such ideas to people who like to break records on the bench.
Safe modification: narrower, intermediate grip for the bench press. If you care about the development of chest muscles, and you have a very strong shoulders and triceps, these muscles might limit you (it is known from research that they take most of the work on the critical point of the bench press, in the concentric phase). This is particularly important during the horizontal bench press. I suggest abandoning the barbell in the bench press, and instead using dumbbells for upper incline (head up flies), dumbbells on the horizontal bench and variations of dips (wider, which minimizes the work of triceps).
Exercise: too narrow grip in bench press (hands very close)
Many people think that this is a recipe for the larger triceps. They couldn't be more wrong: it increases the pressure on the wrist joints, in addition if you keep your elbows close to the body - it's also the elbow joint that suffers. Safe width of the narrow grip bench press is roughly shoulder width apart. The same applies to push-ups (in different versions).
For many people, this exercise will lead to the pain in the sternum area, overload of the elbow and shoulder joints. If for some reason you can not perform dips, look for other exercises. This is is one of the best exercises that builds strength and muscle mass of the chest, triceps and shoulders. Which muscle groups work depends on your technique: greater inclination puts the emphasis on the pectoral muscles, the vertical position: on the triceps. Also a very wide handrails allow to work on the pectoral muscles, and narrow: your triceps.
Sources: Am J Sports Med. 1996 Jul-Aug;24(4):518-27. “A comparison of tibiofemoral joint forces and electromyographic activity during open and closed kinetic chain exercises”. Wilk KE1, Escamilla RF, Fleisig GS, Barrentine SW, Andrews JR, Boyd ML. 2. Int J Sports Med. 2011 Sep;32(9):703-11. doi: 10.1055/s-0031-1277207. Epub 2011 May 17. “Injuries and overuse syndromes in powerlifting”. 3. Am J Sports Med. 2002 Mar-Apr;30(2):248-56. “Injury incidence and prevalence among elite weight and power lifters.” 4. Retrospective injury epidemiology of one hundred one competitive Oceania power lifters: the effects of age, body mass, competitive standard, and gender” – 2006