When it comes to training, there will be little variables that will hold you back. These variables can be broken down into weaknesses, internal (example: being sick), and external (example: weather changes). Though you cannot always control being sick or how the weather will affect your training (lower recovery/cold weather making warm-up longer and joints stiff), you can make sure that all muscles all up to point. When it comes to the most under trained muscle that effects majority of your lifts, strengthening the forearm can greatly improve not only arm mass, but also muscle recruitment of the arm (which leads to greater muscle recruitment throughout the body, because the chain will only be as strong as it's weakest link). When you think of training the forearms what do you think? I am sure most of you think of those grip trainers. Though many have used those with success, I am more concerned with the mass benefits of the exercises I list below (exercises that challenge the grip but work tremendous amounts of muscle). These exercises you can use in any given split if planned accordingly.
1. Farmer Walks
The number one exercise that myself and many others agree on, is the farmer walk. This exercise can be done with a trap bar (also called a hex bar), heavy dumbbells, or farmer walk handles. I would recommend either getting "fat grips", farmer walk handles, welded handles that are wide, or roll a towel over the handles to make sure you are working your grip more than you are tearing up your hands. You can feel badass with torn hands, but being able to farmer walk over twice your body weight is even cooler. I would suggest to mix up days of working distance, and days of working weight/intensity. This will keep your grip being worked without stalling quick. These can be done on lower body days, full body days, back days, hell even upper body days if you plan it right.
2. Double Overhand Deadlift
The second, and least talked about exercise to develop a solid grip is the double overhand deadlift. Recently, I witness every deadlifter using straps. This is due to the is understanding of their purpose. Top level lifters use straps not because they have weak grip, but because deadlifting 800lbs+ does massive amounts of damage to the hand (almost guaranteed being torn each time) to where they save that risk for competitions, rather than tearing their hand every time. Majority of lifters using straps, or the reverse grip actually have not developed a heavy enough deadlift max to utilize either method. Reverse grip still works your hands, but the locked positions decreases the amount of work required. If you are a bodybuilder, recreational lifter, or novice lifter, I would suggest to ditch the straps. Any powerlifter or strength specific athlete, I would suggest only using straps during your heaviest sets. Not only deadlifts, I would recommend any one who does not compete competitively (even those who compete) to do all your exercises without straps besides your top sets (or heaviest sets) of your deadlift work.
3. The Pull-Up Bar
The third best grip exercise (or exercises), yet most individuals never use, would be pullups/slow leg raises/dead hangs. What, pullups, leg raises, and dead hangs? Yes! Pullups initially have you grab the bar in order to perform the exercise, but between the forearms actiavtion at the hand and the forearm activation due to the bicep flexion, the forearms get worked harder than many comprehend. Leg raises and dead hangs may not have the bicep flexion that pullups have, but the tension is just as great. When I say leg raises, I mean actual gymnastic leg raises where you control the negatives for a few seconds and either pause at the middle or go "toes to bar". During the controlled leg raises, the core gets worked hard, but you will most likely feel the forearms working just as hard (if not harder). The time under tension for the leg raises have increased due to being ACTUAL leg raises. Now take away the bicep flexion, and the action of raising your legs. You are now left with the dead hang. The beauty of the dead hang is.....anyone can do it. Even if it is just one minute, thirty seconds, hell, even five seconds. The forearms will recieve benefit to the time under tension. The second reason why dead hangs are listed is because since they are not set weights, no ego is involved, rather, no comprehension of how difficcult the exercise should be is present. This means you can opush your limits without knowing. Maybe you would do farmer walks with 150lbs for 30 seconds. Well, without knowing it, you could have done 200+ pounds for a few minutes. This gives you the freedom to not only judge by the day, but be free of standards and make your own.
4. Plate Pinch Curls
The last exercise I have used in my arsenal of grip strengthening tools would be plate pinch raises/curls. Yes, another multitasking exercise, I know. Though seen as a circus act, plate pinching gives you "pinching strength" which will work the forearms differently than your "crushing strength" developed by the other exercises. Not only will the forearms get added work from pinching two plates together while executing general exercises, but the extra forearm tension in return will activate better muscle recruitment in your shoulders and biceps. This harder the beginning of the chain contracts, the harder the rest of it can contract.
Notice how there isn't any forearm curls or fancy gripper machine exercises? These are real exercises for real results! Give these exercises a go and I promise you you will not only develop a solid grip, but you will have bigger forearms, a bigger back, a bigger neck, and a tougher appearance....hell, I am not to blame for the extra chest hair you grow when adding these exercises, so use at your own risk.