There seems to be two more obvious reasons why physique competitors don't achieve as much definition as they hope to for a show; not applying enough effort, and applying too much of it.
Not applying enough effort is typically due to giving in to food cravings too often and skipping workouts. It should be obvious why this approach doesn't lead to the desired conditioning. The second reason, applying too much effort, is a little more complex.
Overdoing It: An Overachiever's Folly
For starters, there aren't a whole lot of people who test their will power and self-discipline, and make the needed sacrifices in order to compete in a physique contest. The people who do take on the challenge tend to be overachievers.
Overachievers have tendencies to try much harder to achieve success. In most walks of life this can be a good thing, but for physique competition, this can be counter-productive.
A calorie deficit is needed to burn fat. When individuals start dieting and performing cardiovascular exercises while continuing to weight train, they can usually get away with going overboard. They have enough fat stores that the body freely gives them up to provide a source for required energy.
Energy Demands Of A Confused Body
Problems tend to arise as lower levels of body fat are reached though. At this point, competitors have already spent a good deal of time in a mode where their bodies are not getting enough food to support energy demands. Once fat stores start to get a little low, a body says,
And so it takes measures to reduce energy needs and cling on to remaining fat stores. A reduction of energy needs is achieved by slowing the metabolism down. The body goes into a mode where it burns calories at a slower rate in order to get more out of what energy sources it is getting (an indicator of metabolism slowing down is experiencing less frequent bowel movements).
Turning On The Hard Won Muscles
On the other hand, physique competitors probably have an abundance of muscle tissue from all the weight training they've done. Once a body begins to fight to hold onto fat stores from sensing starvation, it becomes more likely that muscle tissue will be broken down to get the energy needed, and this is definitely not what competitors want to have happen.
So applying too much effort is basically doing too much exercise for the amount of energy sources (food) taken in. Consequently, things become more difficult for individuals when they cross the line and enter the over-dieting/over-training stage of contest prep. They will have less energy, feel exhausted much of the time, and their bodies will work against their efforts to try to achieve leaner conditioning.
My Personal Experience: A Prime Example
Case in point, what better to serve as an example than my own experience? I was preparing for my second competition. I was determined to do whatever it took to look the way I envisioned by the time I got on stage. Things were easy at first. I had normal levels of body fat then. My physique was looking pretty sharp at about 4 weeks out, but I didn't have as much hamstring definition as I wanted, and I didn't have striated glutes yet.
Four Week Out Panic
With four weeks to go, I started to panic. I felt time was running out. I started to eat less, and exercise more. I crossed the line and became over-dieted and over-trained. At first, my legs started to feel heavy.
It was an early sign of energy levels getting low. As the days passed and the show drew nearer, I tried harder and harder to get that last little bit of definition. I cut calories even more, and kept increasing the amount of cardio I did. I soon experienced a drastic strength decrease in the gym.
My energy levels became low all the time, but the overachiever in me wanting that added definition marched on and added more cardio in desperation. I was willing to put myself through whatever it took to look the way I wanted to. My metabolism had pretty much slowed to a snail's pace.
I went from about 2-3 bowel movements a day down to 1, and then to every other day, and in the end about once every third day. Now that's a slowed metabolism! I was so over-dieted that I had an insatiable hunger all the time, which made it even harder to adhere to my pre-contest diet.
Contest Day
Occasional cravings are easier to overcome than constant ones. The weight training and cardio I was doing became dreaded, and very difficult to get through. I had no energy and in the end, I got to contest day and was 5 pounds lighter after my 4 weeks of over-dieting and over-training.
There was still no difference in the amount of definition in my hamstrings, and I still didn't have striated glutes. In hindsight, that 5-pound loss was my hard earned muscle!
A Resolution For Next Year
After the contest, I decided that the 4-week period was one of the hardest things I had ever done in my life, and that if I couldn't find an easier way to prepare for a competition, I was going to give the sport up.
The following year I did less cardio, and ate more. I found my energy levels were fine all the way up to contest day. And wouldn't you know it; I showed up with better definition in my hamstrings, and had some striations in my glutes!
Applying too much effort the year before worked against me. I found that contest preparation was easier, and better results were achieved by not trying so hard!
Conclusion
So, if you find your legs start to feel heavy, that your energy becomes low for more than just a short duration here and there, that you have insatiable hunger (even still starving right after a meal!), that your bowel movements become less frequent (slowed metabolism), and that you experience a noticeable decrease in strength, watch out! These are signs of over-dieting and over-training.
Contest prep will be harder, and yield poorer results. Balance those energy resources and expenditures more. Maintain only a slight caloric deficit. Avoid these pitfalls, and preparation will be much easier and more productive. Don't let the overachiever in you lead you astray. Train smarter, not harder.