Thank you for posting here on RacerX VT! Like most exercises, the key is correct form and a controlled ego. Certain ranges of motion take joints, tendons and ligaments beyond the scope of their purpose which leads to injuries. Another issue is trying to take a "safe exercise" and move too much weight. What many individuals don't realize is that lifting heavy weight is only part of the strength curve, slowing down the weight WITH momentum is where things become dangerous as well.
When it comes to cleans and deep squats, there are other ways to accomplish the same results with less risk of injury. What exercises are "ideal" is a result of establishing some baseline assessments to determine which muscle groups are strong and which are weak. Ironically, most athletes lift muscle groups that they are already strong at and avoid exercises that they hate (aka-not strong at!).
If you want to test the strength between your quads and hamstrings, try these two exercises:
Air squats - no weight (http://www.youtube.com/watch?v=SvUxcBYH ... plpp_video
Hamstring press on fit ball - (http://www.youtube.com/watch?v=5f-2PmchHFo
Complete as many reps as you can in 30 seconds-rest 30 seconds and repeat for a total of three (3) sets. Document how many reps you completed within each set.
Compare the total number of reps between your squats (Quad-front of the legs) and hamstring press (hamstrings-back of the leg)
The closer the total number of reps the better "balance" you have between the front and back of the legs.
You asked the question about should you do these exercises? Think about your question this way, do the exercises that I am performing in the gym improve my body position and skill set on the track. It is as simple as that. If your riding coach is asking you to get into the correct attack position and you don't have the strength or flexibility to maintain the attack position for an extended period of time, you know what you need to be doing in the gym to improve your speed and endurance on the track.
If you have any questions or need anything clarified, please don't hesitate to post back here on RacerX VT.