"Why am I not getting stronger?" Probably because you're breaking the rules. Follow these eight rules and save yourself years of frustration and weakness.
Consistency is the name of the game, and the lifter who trains week in and week out will experience steady gains in strength and muscularity over time.
The lifter who trains twice a week for 52 weeks of the year will see better long-term results than the lifter who trains five times per week for just 20 weeks out of the year. You can't hit the gym "every once in a while" and expect to see progress, just like you can't train sporadically throughout the year with any real results. Short-term blasts can be effective under certain conditions, but consistency rules.
Training hard is good. Training smart is good. Combine the two approaches and you've got the best of both worlds.
You do need to train hard, but you don't have to kill yourself every session. Push yourself in each workout, but it's incredibly important to listen to what your body's telling you that day and make adjustments if needed. You also need to experiment to figure out what works best, and what doesn't work, for you. Even though some "meathead" powerlifters and bodybuilders might appear to train haphazardly, many are actually incredibly intelligent and/or intuitive when it comes to sound training principles.
You need to do the big lifts to stimulate muscle growth throughout the body, but you may also need to specialize on muscle groups to fix weak points.
If a muscle never gets activated, it won't grow. To make a muscle grow, it must be stimulated on a regular basis. The deadlift stimulates a lot of muscles throughout the body. The forearms, traps, lats, scapular retractors, spinal extensors, glutes and hamstrings, even the core and quad muscles get activated during heavy deadlifts. This helps explain why deads are such a great exercise. However, if all you did was deadlift, your pecs, delts, and biceps wouldn't come close to reaching their full hypertrophy potential. Make sure your programs regularly incorporate enough exercises that combine to thoroughly hit the entire body.
And here's a common sense alert: If you want maximum muscle mass in a particular bodypart, then make sure you get strong at the exercise that elicits the highest activation in that muscle. For example, hip thrusts elicit the highest glute activation, so even if you're squatting and deadlifting every week, it's worth adding them into the mix if maximum glute size is the goal. Similarly, if rear delt hypertrophy is the goal, military presses won't cut it. You'll need to add in some targeted rear delt work.
Progressive overload is the most important aspect in the strength game. If you embark on a strength training regimen and fail to get stronger, you won't gain much muscle. You must use heavier loads and perform more reps over time.
Bodybuilders may not always train heavy in terms of a percentage of their 1RM, but most successful bodybuilders did focus at least a few years in the beginning of their training life on building strength in the basic lifts. Strength forms the foundation for improvements in other areas such as power production. You have to be able to do something at a moderate speed before you can do it rapidly. For strength-endurance, you have to be able to do something once before you can do it repeatedly. So, plain old simple strength can't be ignored.
As you get more experienced in the gym, you should see dramatic strength progress compared to your beginning level in a squat variation, a deadlift variation, some kind of upper body press, and an upper body pull. And if you want to be your absolute best at anything, be it squats, deadlifts, bench press, power cleans, or even Turkish get-ups, then you need to perform the lifts consistently to groove the neuromuscular patterns and maximize motor learning. Failing to do so will leave unachieved progress on the table.
Failing to take the basic warm-up seriously will eventually and unavoidably end in disaster.
You can't just saunter into the weight room, load a bar with a bunch of plates and grind out a big one-rep max. Even if you do manage to squeeze out that one ugly rep, your injury risk is sky-high. Depending on their condition and injury history, some folks might need 20-30 minutes of general warming up and mobility work to feel ready to train, while others may only need 5 minutes. But everyone must get the blood flowing and the joints and muscles prepared for lifting heavy loads.
Some more simple lifts, such as the hip thrust and row variations, don't require much of a specific warm-up. Once you're generally warm and have completed the sets in your first exercise, you don't need to warm-up for subsequent movements for the same muscle groups. Beginners who ignore the warm-up will learn the hard way to take this component of the training session more seriously.
Form is important, but there is a time and place for using a little momentum and loosening up a bit to go heavier.
Walk into any weight room and you'll typically see people at one end of the technique spectrum or the other. Some lifters are very strict, sometimes too strict as they never use appreciable loads due to their commitment to robotic technique. On the other hand, you find lifters who'd see better progress if they significantly reduced the weight and stopped relying on momentum and generous spotters to complete each rep.
There's certainly some wiggle room in terms of acceptable and efficient form. It's even been shown that slight momentum can increase torque requirements and muscle activation. Your form will also breakdown a bit if/when you test your max at strategic points in the year. A true one-rep max never looks textbook-perfect. If it does, you could've gone heavier.
However, most of the time you do need to be very strict with your exercise form, and you need to learn the right type of form for your body on various lifts. This is especially important for bigger exercises like squats and deadlifts where the risk of injury is inherently higher than, say, dumbbell curls. Failure to pay attention to technique will result in pain and injury, which will stop progress in its tracks.
The best training program in the world is no match for a crappy diet. Your hard work in the gym can absolutely be rendered pointless if you're slacking in the nutrition department.
If you want to build a good physique and perform optimally, then you must take nutrition seriously. You need to take in the right amount of calories and the right blend of macronutrients for your goals and physiology. You don't have to be perfect 24/7, but eating a bunch of crap day in and day out won't let you reach your potential and will prevent you from seeing strength and hypertrophy gains.
Strategically supplementing with protein powder and essential fatty acids is very helpful for improving recovery and setting the body up for growth. I'm a big fan of Metabolic Drive® Low Carb as well as Flameout®.
If you aren't sleeping well or you're mentally stressed out around the clock, your physiology will be working against you.
Some folks need more sleep than others and some can perform well with less, but you should still care about your sleep (quantity and quality) and prioritize it. Make a genuine effort to be consistent with your sleep schedule if you're serious about getting results. Failure to do so will hinder your pursuit of strength and hypertrophy.
Regarding stress, your goal shouldn't be to eliminate it altogether, but rather to optimize it. It's good to be challenged in life, but there's a fine line between eustress (positive stress, like a good workout) and distress (negative stress, like 65 hours a week at a job surrounded by toxic co-workers). Aim to stay in eustress most of the time for maximum results. Step back and analyze your life choices and habits. This is an area in which many lifters can make adjustments that lead to immediate results.