Training with other people all the time. Do you thrive on attention and praise in order to push through a workout? Sometimes you just need to go it alone to build the mental fortitude required to perform at a higher level. I mean Rocky Balboa trained alone most of the time and he seemed pretty talented so that has to be a sign it will work for you too. Gonna fly now...
Moving on to the other end of the spectrum, there’s the chance that other athletes can push you too hard, too often. Peer pressure kicks in and although your instinct says “that’s enough,” you go beyond your safe limitations and become injured. Save it for the competition. That’s where it is nice to have a coach to tell you when to shut it down.
Skipping the warm-up. Warm your muscles up slowly and they will perform better. A gradual warm-up can improve performance. Research indicates muscle fiber exposure to lactic acid just before intense exercise allows the fibers to tolerate even more lactic acid production. The physiology of the muscle fiber can function better at a higher temperature too (up to a point of course).
According to a 2012 literature review in BioMed Central Medicine, a proper warm-up containing “stretching, strengthening, balance exercises, sports-specific agility drills and landing techniques” can be effective for preventing injury. This is unfortunately more involved than many athletes envision when thinking about a warm-up routine and they shy away from it as a result.
At the least, warming-up should be a whole body routine that emphasizes full joint mobility, a gradual increase in heart rate, directional changes, and most importantly, rock music. The warm-up period, especially just before a competition, can be a powerful psychological motivator.
Ignoring joint mobility and flexibility. Some people have really poor mobility. I don’t mean, can you bend over and touch your toes? I mean will your hip flex to a full 120 degrees to allow you to squat all the way down at Crossfit? Do your ankles have the full range of motion necessary to prevent your arch from collapsing while running? Limits in mobility set by a single joint or muscle can impact movement further away than you might realize (ie. ankle movement can change hip movement).
The type of exercise you expect to participate in should dictate what motions you need to improve. If there are specific known limitations, they should be addressed in order to decrease stress on adjacent tissues and regions. Mobility limitation is the reason that the Crossfit “Mobility WOD” exercises exist. The point is that you have to take care of your body with a little routine supplemental work in order to enjoy your regular sport safely and improve performance.