What is the best workout routine for a very busy individual?

Nobody really needs to spend hours at the gym to gain benefits from their workouts. Also spending everyday doing some form of exercise is also not necessary to get strength and fitness.
Anyone looking for an adequate weight training routine to fit around a busy lifestyle and work schedule. In the following paragraphs I will try to give some useful information and a workout routine that will suit this type of individual.
Progressive Training is the quickest way for anyone to build strength and muscles. This type of training focuses on the individual adding additional weight to the bar for each exercise everytime they workout.
Since this type of exercise requires you to progressively lift heavy weight you will only need to focus on doing 3 to 4 set of 6 to 8 reps for each exercise. This greatly cuts down on the amount of time you need to spend on your workout.
Having plenty of rest when doing a heavy workout routine is also important since this is when your body repairs muscle tissue and starts to build some new fibres. This frees up time for you to pursue your busy work schedule or other interests.
Any decent workout routine needs to exercise all the major muscles groups. So compound exercises like Squats, Deadlifts, Bench Press, and Barbell Curls are the ones to include in a weight training routine.
Before starting to do any type of heavy lifting you should do some type of gentle warm up such as spending 20 to 30 minutes on an exercise bike. This type of warm up will get the blood flowing freely around the body as lifting heavy weight from a cold start is not something you should do.
A Solid Workout Routine For A Busy Individual
  • Squats
  • Bench Press
  • Upright Barbell Rows
  • Barbell Curls
  • Deadlifts
3 to 4 sets of 6–8 reps (dependent on current strength and condition) of each exercise
Weekly rotation: 
Week 1: Workout - Mon, Wed, Fri, Sun … Rest - Tue, Thu, Sat
Week 2: Workout - Tue, Thu, Sat … Rest - Mon, Wed, Fri, Sun
Following this schedule of rotating the days you workout will make sure their is a rest day after every workout day. So one week you will be weight training 4 days and the following week you will be training only 3 days.
All the exercises in this weight training routine are compound exercises which target all the major muscles groups of the body. You will only need to do this routine 3 or 4 days a week which should be completed in about an hour.
Since you are looking to add extra weight to the bar for each exercise every time you workout. You will not need to alter the amount of sets or reps you are doing to progress. So this will not increase the amount of time you are weight training.
On commencement of this workout routine you will more than likely need to experiment with the weight you are lifting to see where your maximum is. You want to keep the correct form throughout the exercise to avoid muscle tears or injuries.
Struggling at the beginning to even complete the correct number of sets and reps will not help you in the long run. It's best to complete all the exercises even if you have to start with lighter weight than your body is capable of lifting.
Over the coming days and weeks your body will be adding more muscle and strength to all areas of your body. So progressively adding more weight to the bar will become easier to achieve and not result in you failing to complete a workout routine.
At each workout session you should aim to add between 2 and 5 lbs total to the bar. This will stimulate your body into adding more muscle to give your body the strength to cope with the constant increase in weight when lifting.
You should also backup all this exercise by consuming enough protein through your meals ideally or through protein shakes to help repair and build new muscle tissue. Also on the days you workout you should consume more carbs in your food which gives you the energy to perform the heavy workouts.

Read more here about the science behind gaining muscle quickly