To gain weight in the form of muscle you will need to eat more calories than you
burn off each day. If you choose to do cardio, low-intensity cardio is the way to
go. This will keep the fat off and to maintain general fitness whilst minimizing the effect on gains.
As someone earlier mentioned, do cardio after weights. That's what i do but i take it easy on the cardio. Since your aim is to build muscle and gain weight then you should keep cardio to no more than 3 times a week. Make sure to consume plenty of calories to make up for the cardio.
As for working and rests. Definitely take day/s off to recover because you don't
grow in the gym! You grow while you are in deep sleep, which is the time when your body will produce growth anabolic hormones for muscle growth.
Before you workout eat carbs and protein. Because when you workout you will be tearing muscle fibers and depleting your muscles of it's glycogen supplies. To
refuel after working out you should consume SIMPLE carbs and some protein. Also a protein shake comes in really hand after your workout.
IF you don't have access to a gym or weights. Then there really isn't much you are going to gain out of body-weight exercises (as others have mentioned) as your muscles will 'adapt' to your body-weight. Though you could add a load of textbooks in a backpack and perform pushups with them lol.
You should eat every 3 hours-4 hours. Go for 5 meals a day.
Make sure there is some kind of protein in each meal. Tuna is a cheap source of
protein and eggs are too.
NOTE:make sure to eat the yolk because it has vitamins which are always good for you, some eat the egg white only because it has no fat content in it which i think is silly because you are missing out on vitamins/minerals.
If you haven't tried kangaroo meat, try it. It is a very very good source of protein as others have mentioned.
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To the people who have access to a gym:
You guys probably already know the stuff i'm about to write about here but i'm going to include this in my post for others who might pick up something new.
There is the full-body workout routine and there is the split-routine.The split
routine is a weekly routine where you work out your different muscle groups over different days of the week. The advantages to the split routine is that you won't be spending an average of 2 hours in the gym; also you will be able to maximise your gains more efficiently if you allow a specific muscle or muscle groups to rest.
There are two popular ways of training utilising the split routine: push/pull split
routine OR the upper/lower body split routine.
Day 1: Push (chest, triceps, shoulders)
Day 2: Rest
Day 3: Pull (back, biceps,forearms)
Day 4: Rest
Day 5: Push [legs] (glutes, hams, quads)
Day 6: Rest
Day 7: Rest
Ab workouts can be done on days 1,3,5
The above workout routine would be suitable for beginners.
For the hard-gainers the routine can be intensified with the below routine.
Day 1: Push (chest, triceps, shoulders, legs)
Day 2: Pull (back, biceps, forearms)
Day 3: Rest
Day 4: Push (chest, triceps, shoulders, legs)
Day 5: Pull (back, biceps, forearms)
Day 6: Rest
Day 7: Rest
This allows for just enough time for your muscle groups to recover while training
them twice a week.
Compound exercises are an excellent way to build muscle mass these include: bench presses, dead-lifts, squats. Though it can be extended to other exercises such as: standing (more difficult than the seated military press) military presses, pull-ups (if you can't perform a pull up, use weight-assistance OR alternatively use the lat pull-downs cable machine), bent-over rows, dips etc
Anymore questions please post. I apologise in advance if there is anything i haven't made clear.