The real problems begin, however, in poses requiring full extension (straightening) of the hip joint. These poses include backbends such as Setu Bandha Sarvangasana (Bridge Pose) and Urdhva Dhanurasana (Upward-Facing Bow Pose), where both hips are extended, and standing poses like Virabhadrasana I (Warrior Pose I) and Virabhadrasana III (Warrior Pose III), in which the legs open forward and backward (front leg hip flexed, back leg hip extended). In all these poses, tight hip flexors can cause painful compression in the lower back, a fairly common problem in backbends.
Longer rest periods are more ideal for making progressive tension overload happen, and shorter rest periods are more ideal for generating metabolic fatigue. So, if you’re doing an exercise that is better suited for progressive overload (i.e. primary compound exercises), you’re going to want to rest longer between sets to maximize strength output. And if you’re doing an exercise that is better suited for metabolic fatigue (i.e. isolation exercises), you’re going to want to rest less between sets to make that happen. And if you’re doing an exercise that is suited equally for a combination of the two (i.e. secondary compound exercises), you’re usually going to want a moderate rest period somewhere in between.
Objective: Are you getting stronger? Increasing either weight or reps? If you're measuring individual markers on a daily basis like vertical jump, grip strength, or resting heart rate then what sort of trends are you noticing in these variables? If they're staying the same while your strength is increasing, then you're recovering well. If they're decreasing and you find yourself weaker over time then you're not recovering well.
Most problems with the hip flexors, however, don't originate in a lack of strength but in a lack of flexibility. To understand how these muscles lose their flexibility, imagine someone with a broken arm, her bent elbow encased in a plaster cast. When the cast is removed after six or eight weeks, the soft tissues around the elbow (muscles, tendons, ligaments, and even skin) will have shortened, and the elbow won't straighten out. It will take patient stretching over several weeks to restore the range of motion. Similarly, if the hip is constantly kept in a flexed position—like sitting—for hours every day, day after day, the hip flexors will shorten and shrink, limiting your ability to fully extend (straighten) the hip.
Secure a flat resistance band just above your ankles and stand with your feet at about hip width, keeping feet forward. Keeping your weight in your heels, step your right foot laterally, maintaining the tension in the band. Keep the band taut as you step your left foot slightly to the right. Continue stepping sideways to your right for about 5 steps. Then step to your left to return to the starting position. Repeat three times.
In addition to the HIIT sessions, it’s always a good idea to go for a 30–60-minute walk as many days per week as you can. I recommend getting a minimum of 10,000 steps every day. Use a phone app to track them. If you’re into jogging, swimming, hiking, or some other form of long-duration, fairly low-intensity cardio, that is fine to do as well, and as often as you like.
It has been argued that purposely overtraining for a brief period can be beneficial. One article published by Muscle & Fitness magazine stated that you can "Overtrain for Big Gains". It suggested that if one is planning a restful holiday and does not wish to inhibit their bodybuilding lifestyle too much, they should overtrain before taking the holiday, so the body can recuperate and grow during the prolonged rest period. Overtraining can be used advantageously, as when a bodybuilder is purposely overtrained for a brief period of time to super compensate during a regeneration phase. These are known as "shock micro-cycles" and were a key training technique used by Soviet athletes.