Effective training involves a continual process of overload and adaptation. That is, consistent workouts produce a stress (overload) that your body seeks to alleviate by growing stronger and more fit (adaptation). As your physical capacity improves, more is required (i.e. you must run faster, lift heavier weights, spar longer or with greater intensity) to overload your system and affect further positive physiological adaptations. Unless you gradually ask more from your body, your training will yield minimal improvement.
However, if you push too hard, too quickly you risk overtraining or injury. For this reason, "fighting shape" is best attained in a systematic, step-by-step manner. For example, training typically encompasses four distinct stages: (1) base conditioning, (2) intensive preparation, (3) pre-fight restoration and (4) post-fight recovery. Because each fighter has individual needs and limitations, and different types of training equipment at his disposal, below is a general guideline of what each phase entails.
The goal of the base-conditioning phase is to build up the cardiovascular system, lung capacity, and muscular strength and endurance. The bulk of your aerobic conditioning should be performed at 65-80% of your maximum heart rate for periods of 20-60 minutes. This is also the period to focus most intently on addressing and correcting any technical weaknesses you may have, as well as adding new fighting skills. The base conditioning stage can last anywhere from 2-16 weeks, depending on several factors, including your current level of fitness and whether you have a match scheduled in the near future.
Once your base conditioning is established and a fight is scheduled, you'll enter the intensive preparation phase of your training. The purpose of this stage is to prepare you physically, mentally and emotionally for the specific demands of an actual fight. Predominantly anaerobic workouts, performed at 80-95% of your maximum heart rate for 20 minutes or less, become more and more frequent. Sparring becomes increasingly intense, often against fresh opponents rotating in every 2-3 minutes. During these weeks your skill training should focus less on acquiring new technique and more on making the most of your existing strengths. This intensive preparation phase lasts between 4-6 weeks. Training at this intensity for more than six weeks increases the likelihood of overtraining. Less than four weeks in this stage won't allow your body enough time to sufficiently adapt to the rigorous training.
The week before your match training transitions into the pre-fight restoration where the goal phase is to gradually cut back the volume and intensity of training so that your body re-absorbs energy to full-capacity. Don't lift weights during this stage. Instead allow your muscles to fully recover from the rigorous training and replenish glycogen stores. If you compete on Saturday, your last hard sparring session takes place on the previous Monday. Each day that follows reduce the volume and intensity of your workouts by about 20% (in addition to not lifting weights). Tapering down training volume and intensity after several weeks of extremely rigorous workouts will leave you fully energized and mentally eager to fight - both essential components of a peak performance.
The final stage consists of spending 1-2 weeks in a post-fight recovery phase where you are engaged in active rest. Active rest activities are unrelated to fighting, are less structures, allowing for more variety while providing a mental respite from the intense competitive focus. Physically remain active while giving your body a reprieve from the repetitive movements and stresses associated with fighting. It is an essential component in your training cycle and will leave you refreshed and ready to begin another training cycle.