Another muscle, the rectus femoris, can also limit hip flexion and cause problems in yoga poses. Part of the quadriceps muscle on the front of the thigh, it originates near the ASIS, runs down the center of the thigh, and inserts on the shinbone (tibia) just below the knee. When the rectus femoris contracts and shortens, it not only extends or straightens the knee, it also flexes the hip.
See what I mean? Notice, how I said the “fatigue of failure”. This is because one must interpret their fatigue properly. (1) Some go past failure thinking something magical is going to happen, when only damage will occur. (2) Some feel slight fatigue, aren’t close to failure, and should keep going to enter in the actual sensation that matters: failure. (3) Some are very close to reaching fatigue, but misinterpret the sensation as failure and stop, when they were only moments away from feeling something they never felt before.
Many people eat two or three meals a day and the occasional protein shake (when they remember), and then wonder why they're not putting on weight. To increase muscle mass, you have to have excess energy (calories and protein) in your system - supplied by regular small meals throughout the day. Most people have no idea how many calories they need. Do you? You may find that eating until you're full is not enough, especially if you're eating the wrong sort of calories (i.e. all carbs and no protein!). Protein is the priority followed by carbs then fat, but all are important and play a part in building mass and size.

We’ve broken down the nine exercises into three sets of three. Before you begin each set, set a timer (or workout near a watch with a second hand.) If you are just starting to work out, do each exercise as hard as you can for one minute, followed by the next, until you complete the first set. Then, take a one minute break before moving on to set two, in which the exercises should also be performed for one minute each. 
The good news is that there are plenty of good hip stretches out there that you can do to relieve discomfort, decrease tightness, and increase mobility in your hips. Since your hips are involved in so many of the movements you make (both inside and outside of the gym) stretching them is a great way to keep them feeling good and ready to work for you. Add some of the 12 hip stretches Atkins demos below to the end of your workout, or spend 10 minutes each day just doing a few of them, to improve mobility in your hips.
Reaching failure matters because tension matters. Failure is when the muscle cannot generate anymore force. Which means one applied (worked out) enough tension through the muscle to just want to give up. And guess what? Carrying groceries can do this for some. Why? We are all at different strength levels. So don’t worry about other people and what they can or cannot lift. I say this because FAILURE can be achieved with either light weights or heavy weights.
To avoid hip flexor pain, you should pay more attention to these muscles, Dr. Siegrist explains. When you are seated, your knees are bent and your hip muscles are flexed and often tighten up or become shortened. “Because we spend so much of our time in a seated position with the hip flexed, the hip flexor has the potential to shorten up. Then, when you are in a hurry because you are running to catch a bus or a plane, or you trip and fall, the muscle could become stretched. Here’s this stiff, brittle muscle that all of a sudden gets extended, and you could set yourself up for strain or some hip flexor pain.”
Just like building any other muscle. The slower we go, the longer the rep will take. This time under tension is what builds the muscle. We can use light weight or heavy weight, either way, fatigue is what matters. If slower equals growth then that means going heavy equals growth (because lifting heavy is lifting slow, otherwise you are lifting light) and this is true, BUT, we can create growth with light weight as well. We just have to lift the light weight until it feels heavy so our tempo changes. If we can lift a weight heavy then it’s too light, so either go heavier or keep lifting that light weight until it feels heavy. Going heavy as possible in the start just expedites the process. Heavy is a relative term, so don’t try and compete with others. Measure your own strength. Personally, I enjoy medium weight with medium reps. Just pump them out. If I go heavy heavy, this would mean I would need a weight that I can only rep 3–4x. If I can rep a weight more than 12x without getting tired, then it’s way light. But, like 8 reps, with the last rep being the hardest is how I roll. KEEP READING.
The G-med and G-min perform similar functions, depending on the position of the knee and hip joints. With the knee extended, they abduct the thigh (out to the side away from the opposite leg). When running, they stabilize the leg during the single-support phase. With the hips flexed, they internally rotate the thigh. With the hips extended, they externally rotate the thigh.

How to do it: Begin with one foot firmly planted in front of you with your other leg extended back. Keep balance by putting your weight in the ball of your front foot and the back heel of your back foot. Hold a dumbbell in either hand, arms at your sides. Or, place a resistance band under the foot of your working leg, up, and around the same shoulder. Stand tall and bend your front working leg to approximately 90 degrees, keeping your knee directly over your ankle so it doesn’t over-extend. Return to the start position and repeat. Do both sides.
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