If you have been training with weights consistently and at high intensity for a while without a planned reduction in your training volume, adequate rest and nutrition, then you are holding back your ability to adapt to the training stimulus. This can mean an inability to hold onto lean mass, storage of unwanted fat and increased risk of the common cold or flu.
You can flog a dead horse until the cows come home, but unless you’re recovering, it doesn’t mean sh*t. Often the difference between a successful athlete and a non-successful athlete is how well they can recover and stay 
healthy. A mentor of mine once said, “training is like medicine, you need the right application and dose.” Too much or too little won’t give you the desired outcomes. Getting the dose of training along with appropriate recovery strategies is the recipe for success.
The whole premise of training is to adapt to the stimulus that you are exposing yourself to. When you lift weights or go for a run, you are exposing yourself to stress and your body will respond accordingly. E.g. Cardio training will help capillarization, ↑ stroke volume, ↑ mitochondrial density and resistance training will ↑ muscle cross-sectional area, ↑ strength/power output etc. (3, 4) Contrary to what most people think, the results come from how well you rest after the exposure to training.
Nutrition, sleep and taking care of mental health are paramount to adequate recovery with no exceptions. (4) Your body is an organism that requires all of those elements to thrive and when you throw a stressor like training into the mix, they become a whole lot more important.
If you have been training with a coach or a trainer for longer than 12-weeks and haven’t heard the term “de-load”, you should be VERY worried. Either the 
trainer doesn’t know the importance of the reasons to de-load or they think you haven’t been working consistent or hard enough to warrant a de-load into your training program.
What is a de-load? I’ll give you a clue, you can’t do it in the iTunes store. Basically a de-load is a short planned period of recovery to allow your body to adapt from the accumulated fatigue. Generally it’s not a complete rest with no training, it’s just a week with some modifications to ensure continued improvement. This is where the magic happens and the results come from. If you are interested, see the Nerd Section at the end of the article for detailed information.
Recently I experienced the positive effects of an unplanned de-load in my own training block. After switching to high volume type training and moving away from strength as my primary focus, my squat had a significant drop in strength much to my disappointment, whilst training with my coach. However the next time I hit my squat I felt like a million bucks and my strength was back. I reported back to my coach that I was superman and managed to get my strength back despite the high volume training. After chatting with him we worked out that with my schedule change that I hadn’t squatted for 10 days, hence the unplanned de-load and the increase in strength. Regardless if the goal is strength, power, muscle growth or even reduction in body fat, don’t be a chump and think you don’t need the rest.
3 ways to de-load to get better results
Reduce kgs lifted. E.g. Can lift the same reps/sets but with a lower weight (10-15% reduction)
Reduce the volume (reps x sets). E.g. Stay at the same weights (intensity) but reduce the volume through either sets and reps. This method works best for strength and power athletes
Supplement different exercises in place of others. Please note this method is harder to quantify and regulate, be careful you don’t over train. Monitoring strength can be a good way to regulate.
Note all the above methods can be applied to other styles of training, not just resistance. E.g. can be applied to cardio, if you’re monitoring the volume (km).
There are certain personality types that don’t deal well with the concept of rest and despite telling them that rest days are part of the actual program to benefit their results, they will not listen and train anyway. This generally happens with people who are either overly ambitious (and ill-informed), addictive type personalities or have a bad relationship with food. A good coach will be able to identify this and use strategies that can ensure adequate recoveries through education and programing.
Next time when you have your planned rest, don’t feel guilty and remember that you are moving closer to your goals by allowing your training to adapt. The keys to effective rest are quality sleep, adequate nutrition, hydration, mindfulness practices, rehab or prehab training, ice baths and massage.
Recover well!
Adam
[optinform]
Nerd Section:
The aim of training programs is to elicit appropriate responses in both physical and psychological to the imposed stressors. The longer the athlete/person is exposed to these stressors without change, the body will experience performance plateaus or even reduced performance. In some cases, increased risk of injury, illness and other symptoms of overtraining will be experienced. To offset this and to have continued improvement, a long term planned program with variations in specificity, intensity, and volume within the overall program. This long termed type of program design is called periodization. (1)
Photo credit Wikipedia
With correct periodization strategies, the outcomes can be explained by the General Adaption Syndrome, also referred to as supercompensation. (5) It is a four-step process. Step 1 is the application of training and the body’s reaction to the training stress. Step 2 is the recovery phase or active rest. This phase will result in the energy stores and performance returning to baseline (homeostasis). Step 3 is the supercompensation phase, with a positive reaction from the stressor gaining an improvement. Step 4 is the loss of the supercompensation effect, when there is a decline straight after the peak. (2)
References:
- Baechle TR, and Earle RW. Essentials of strength training and conditioning. Human kinetics Champaign, IL, 2008.
- Gambetta V. Athletic development. Champaign: Human Kinetics Publishing 2007.
- Pesta D, Hoppel F, Macek C, Messner H, Faulhaber M, Kobel C, Parson W, Burtscher M, Schocke M, and Gnaiger E. Similar qualitative and quantitative changes of mitochondrial respiration following strength and endurance training in normoxia and hypoxia in sedentary humans. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 301: R1078-R1087, 2011.
- Powers SK. Exercise physiology : theory and application to fitness and performance. New York: McGraw-Hill, 2012, p. xv, 587, [536] p.
- Selye H. Stress and the general adaptation syndrome. British medical journal 1: 1383, 1950.