90 degree's only. Too much pressure on the shoulder capsule beyond this. Now if the load is light enough and you can keep your scapula together than you are okay but if you are benching and the weight goes beyond 90 degree's and your shoulder blades can't retracts all the pressure is on the anterior part of the shoulder.
Now with this said I call on Paul Chek (IMO the expert). Here is what he says.
Paul Chek
Why all the fuss over a big bench-press? What does the sheer amount of weight that someone can push whilst lying flat on their back have to do with anything? If you’re sitting with a bunch of guys and someone strong walks in, it’s common to hear "I wonder what he can bench?" Or when discussing sport, the same question comes up, "How much can so-and-so bench?" When I go to a party and meet people, you can be as sure as the presence of beer that someone will ask, "What can you bench?" It is always great fun to see their reaction when I tell them "Not much, but I can run 30 meters flat out with Malu Mainu’u on my back!"
The bench press exercise was never intended to be a benchmark of man (or woman!) hood. It is an exercise for improving the size and/or strength of the chest, anterior deltoids and triceps, nothing else. In fact, the star player on any team is rarely the one with the biggest bench press! Unfortunately, over-emphasis on the bench press often coupled with poor technique has led to a high incidence of shoulder injuries in both athletes and non-athletes. Additionally many people are not anatomically designed to perform the exercise as it is generally taught in most strength training texts, Personal Trainer certification courses and by many strength coaches.
THE PROBLEM WITH TRADITIONAL TECHNIQUE
The bar is lowered until it touches the chest and then pressed back up to the start position. Everyone is expected to lower the bar to the chest; anything less is considered poor form, sub-standard, and even wimpy by fellow lifters. However, to perform the exercise under such guidelines requires a greater range of motion (ROM) than is found in the shoulder joint of most people - particularly male athletes. Why is it so important to work within the ROM of your shoulder joint? Some simple anatomy will help to explain this.
The movement-restricting factor during a bench press is not the muscles of the shoulder; it is the special connective tissue casing around the shoulder joint called the "joint capsule." This highly specialized structure is anatomically designed to not only allow just the right amount of motion to prevent joint damage, but also contains thousands of specialized nerve endings called "proprioceptors." Proprioceptors are special nerve endings that communicate with the brain to inform it of joint position and speed of movement, as well as pressure, tension and pain in and around the joint. Loading the shoulder and forcing it beyond the functional ROM limit will stretch the shoulder joint capsule. In most people this will occur by letting the bench-press bar travel until it touches the chest.
Additionally, because the bench press is performed on a flat weight lifting bench, normal movement of the shoulder blades (scapulae) is disrupted. This demands that more movement must occur in the shoulder joint itself. As the bar is loaded with heavier and heavier weights, the shoulder blades are pressed into the bench harder and harder, further disrupting the normal mechanics of the shoulder girdle joints and overloading the shoulder.
HOW FAR SHOULD YOU LET THE BAR TRAVEL WHEN PERFORMING A BENCH PRESS?
To protect the shoulder joint capsule from being stretched out or injured the exerciser must determine how far to safely lower the bar. It is essential that each person determine optimal bench press range of motion for his or her own shoulders, as each person is different.
The Bench Press Range of Motion Test
Step 1 - Passive Range of Motion:
Place your arm in the bench press position and allow your arm to lower to its passive end range of motion. This is the position where the arm naturally stops without being forced. At this point you have determined the exact point at which the shoulder joint capsule becomes the primary restraint to shoulder ROM.
Step 2 - Optimal Bottom Position:
Once you have identified the end position of passive shoulder range of motion with the Bench Press Range of Motion Test, lift the arm 2-3cm to find your optimal bottom position for the bench press exercise. This creates a small buffer zone (10º - 15º) which will protect the joint capsule from overload when the weights get heavy or when you get tired.
Although many will argue that you must train through the "full range of motion" to be strong for sport, this concept is unfounded. It is well known among Physiotherapists and exercise scientists that there is approximately a 15º +/- carry-over of strength developed at any specific joint angle with strength training. i.e. if you train the shoulder from 15º to 75º, the strength gained will carryover from 0º to 90º. This is how sports medicine doctors improve strength in an injured shoulder or knee without actually ever moving the joint through the painful ROM.
What’s so important about training within your given ROM?
What most trainers, athletes and coaches don’t seem to respect is the fact that training beyond the shoulder’s passive barrier with heavy loads will stretch the shoulder joint capsule. Once stretched, the joint capsule can no longer stabilize the shoulder joint with common arm movements such as swimming, hitting a volley ball or netball, holding power tools over head or even swinging a hammer. If these arm movements are repeated without the stability provided by a functional shoulder joint capsule, an impingement syndrome develops, resulting in inflammation and pain in the shoulder joint. Bursitis and rotator cuff tendonitis commonly develop secondarily. Because the shoulder joint capsule provides critical information about arm position, those with a loose joint capsule often lose their ability to accurately sense joint position. This will result in a loss of accuracy in sports requiring precision placement of the arm.
In any sport, your arm rarely ever reaches a loaded end point in the same position twice in the same game or event. Because the loads in sport are both brief in duration and seldom as high as those encountered during a bench press session, the shoulder joint capsule can recover from intermittent exposure to end range loading. For those with insufficient range of motion to perform the traditional Bench Press, going to the gym and lowering heavy loads to your chest with slow speeds of movement, 30-100 repetitions or more per week is like repeatedly crashing your car into a brick wall at slow speeds just to prepare for the one day you may actually have an accident!
WHAT DO I DO IF MY SHOULDERS ARE TRASHED AND I STILL WANT TO BENCH PRESS?
If you have painful shoulders when bench pressing you may not need to stop. To safely return to bench pressing, follow these guidelines:
Spend 4-8 weeks performing a rotator cuff conditioning program. For more information on rotator cuff training I recommend the book Seven Minute Rotator Cuff Solution by Horrigan and Robinson.
Begin your return to the bench press from the floor, not a bench. The floor creates a range of motion barrier, protecting your shoulder joint capsules and tendons from excessive stretch.
Always start with dumbbells. Dumbbells allow your body the needed freedom of motion to find a new bench press pathway that does not stress the injured tissues.
Once you have performed 3-4 weeks of floor bench press, progress from the floor to a slightly deflated 55-65cm Swiss Ball (Figure 5). The Swiss Ball will allow a slightly greater range of motion than the floor and will increase stabilizer activation. A C.H.E.K certified intern can teach you how to perform many Swiss Ball bench press variations.
After 3-4 weeks on a deflated Swiss Ball, progressively inflate your Swiss Ball. The firm ball will allow slightly more shoulder joint motion as well as increased shoulder blade motion.
Having performed the above steps, use the test described in Figure 2 to assure that you don’t exceed your shoulders safe bench press range of motion. Progress both volume and intensity slowly. If your shoulder(s) begin to show signs of discomfort with the traditional bench press, revert back to the previous steps in the progression and avoid the traditional bench press all together!
References
Chek, P. Strong 'N' Stable: Swiss Ball Weight Training, videocassette series. San Diego, CA: Lenny Magill Productions/Paul Chek Seminars, 1997.
Chek, P. Gym Instructor Series: Vol. 2 Pushing & Pressing Exercises, videocassette. San Diego, CA: Paul Chek Seminars, 1997.
Hartmann, J. & Tunnemann, H. Fitness & Strength Training for All Sports. Toronto, ON: Sports Books Publisher, 1995.
Horrigan, J. & Robinson, J. The 7-Minute Rotator Cuff Solution. Los Angeles, CA: Health for Life, 1991.
