Wow so much I wanted to reply to but it would have taken way too long. A few highlights though.
Most injuries that have to do with weight lifting are what are called overuse injuries. The can come from machines, free weights, or doing any repetitive motion too many times. I would say improper use of equipment causes more injuries than it being a specific type of equipment being responsible. Careless form with free weights, or improper set ups on machines that hold you into their movement patterns would probably come out equal.
Having a hard on for one movement pattern and doing it way to frequently also sets the stage for injury. Hence why you believe that pushing exercises cause more injury. People fugging love to bench press!!!!! Just as much of a point people naturally tend to have a major imbalance of pushing exercises to pulling movements in their programs. Most people do not work out what they can not see as often. I am in this category too. I love a good push workout! They are so fun and honestly you can push yourself as hard as possible and still not feel run down after a push workout because the muscles are smaller. Try a crushing back workout like that and you are fugging done for the day. SO MUCH MORE MUSCLE BEING WORKED ON PULLING MOVEMENTS!!!!
So add the fact the front side of the body/ push group is typically trained at a 2:1 ratio compared to back and that also explains why you would see more overuse injuries in push groups. However that does not mean that back training is safer because there appear to be less injuries. It just means the back / pull groups are being trained less, so there are less training related injuries.
As far as older people lifting heavy goes. There are too many variables with that however I will say this. Heavy is relative to each person, and the rep range being worked in. Someone working in the 15 rep range can lift heavy for that rep range. In other words they can be at or near the point of failure at 15 reps. That is a HEAVY set of 15. You know it is heavy because it feels that way. Heavy is relative so if it feels heavy. IT IS!!! Now say you took the weight he did for the heavy set of 15 and had him do a set of 5 it would be a very light set of 5.
However I can tell you that a body builder type routine where you are doing 25+ sets lifting 75-85% 1RM in the 6-15 rep range is far more abusive to your connective tissue than a typical strength based program using 85-95% for 3-10 sets in the 3-5 rep range. The difference in volume and stress on the joints there is MASSIVE!!!!!
As an example my max on Deadlifts from the meet was 606. So lets look at the massive difference in volume here using rep numbers in the middle of the rep range and weights from the middle of the range for intensity. This is just what one set of deadlifts in those ranges would compare volume wise.
Hypertrophy Range 80% = 485x10 = 4850 lbs volume in 1 set
Strength Range 90% = 545x4 = 2181 lbs volume in 1 set.
Which do you think your connective tissue could recover from better. Keep in mind the deeper the hole you dig, the more it requires to fill it.
Now keep in mind the Hypertrophy aka "light" weight training also does multiple sets of multiple exercises ending up around 20-40 sets by the end, and the typical strength program will have from 6-15 sometimes up to 20 sets for a given body part and that the accessories are not done to failure, and we are talking about easily doubling the total volume with a hypertrophy based workout where most of the sets are performed very heavy for their rep ranges. So that is a lot more stress on the connective tissue. It is digging a deeper hole.
The bottom line is that with age volume, and frequency have to be adjusted to allow for recovery ability. To keep strength training in the picture some of the volume has to come down in the accessories to have a healthy balance. To push the volume, you want to do less strength focused work to have a healthy balance. Heavy lifting unless having true traumatic injuries is excellent for you and stimulates your connective tissue.
My joints have been healthier the last 2 years where I have been focusing on strength, and using accessories to get some of the volume for growth but the accessories are never pushed to failure, and typically don't go over an RPE8 on them.
By the way the reason older people need more time to recover is that we produce less collagen. It is typically not the muscle healing that is a problem for us. Instead it is a slower recovery process in the connective tissue due to less collagen. This is why older guys on HGH do very well the HGH increases the collagen. It is the natural drop in GH that causes the drop in collagen production. So there is an extremely logical reason why frequency has to be adjusted for older guys working in the upper ends of their strength curves.
Getting older doesn't mean you can't lift heavy anymore. It means if you want to that you need to be smarter about it. However believing that a hypertrophy based workout will limit injury is also wrong unless you are just going through the motions and doing pump work. It is best to rotate the goals around a bit. Only buckling down on one facet or the other when you have a goal that requires that level of specificity.
Also the mention that push exercises might cause more injury due to the reversal of direction at the bottom of the movement being compared to throwing something up and decellerating it when you catch it is a great theory but only holds water for someone who is actually throwing the barbell and catching it. There are no sheer forces, or violent changes of direction in controlled lifting. You can perform a rep like that intentionally yes but that is sloppy lifting. Now you can use the stretch reflex to get more oomph an explosiveness out of the bottom. However that is often done by advanced trainees, and most new guys don't understand or no how to perform that properly unless shown. Either way though a controlled press is never going to produce the drop and catch level of impact referred to. Even during explosive reps like say doing 135 on bench as fast as possible, you still have to decellerate it at the top to stop it. Then it should be lowered under control.
Now on to the Form Nazis - here is the most important thing you need to know about form. STAY TIGHT! That is it. Thats the end of the form lecture!
No really, natural movement is not linear or perfect. There are some definite no-nos out there for certain exercises. However there are entirely too many variables in the human skeletal anatomy to say this is the optimal form for everyone. Also if you only ever train in perfect angles you tend to injure yourself in regular life when you have to suddenly be explosive, or strong in a position your body is not used to doing so with. The bottom line is when you lift you need to stay tight everywhere. You should be engaged completely and if you are then you are not likely to get injured.
Again let me reiterate this especially for anyone who learned a lot in the 90's or early 2000's when EVERYONE WAS A FORM NAZI! That was when all the PT Certs started telling people to only bench to 3-4 inches of the chest, or don't protract your scapula at the top of a pull up or pull down. All kind of things limiting compound movements trying to isolate certain muscles, effectively negating the purpose of doing compound movements in the first place. It all just went haywire and so many people are still stuck on that information. However the reality of it is that setting up properly, getting tight and staying tight are the most important parts of what people call "form". If you stay tight then you are protecting everything as much as possible.
You need to train in and be strong in all angles and directions. You should train with odd objects, and sometimes even intentionally offset weights. You want to remain injury free you need to make sure you are strong everywhere, every angle and every direction.
As far as training to failure and keeping form, that is not possible. If you train to concentric failure you will indeed lose form. Failing on the final rep is breaking form. It was not done to complete ROM and that is not proper form unless partials were intended for the last rep.
I am sure there was more but I love the fact there is so much thought being put into things in here.