Neither picture is a no-rep however one is more efficient than the other and both can be used in different scenarios.
The picture on the left is in a better position (depicted by the triangle/lines) for more efficiency and higher reps. This position might be harder if a person has tight hamstrings, lower back, and shoulders. Some points of performance that would help this position: - push your shoulders and body away from the bar (think push back)
- keep feet together
- big arch/hollow in the kip
- limited range of motion? Drive knees then kick feet
- this position can also allow for straighter leg kips allowing you to breathe and/or bent knee kips allowing you to get faster reps.
The picture on the right is not in a good position for efficiency, however when performing strict toes to bar this might be optimal. When moving slow, controlled, and without a kip you are now forced to contract your trunk more but raising the height of your hips. Getting the shoulders back is much harder hence rolling the truck is how we get the toes to the bar. Strict T2B and strict movements in general are easily overlooked but great tools for strength and technical development! Use this tool in training but never in a game-day scenario when asked to exercise for time.
A great tool we use to help efficiency and skill development is to practice slower and faster variations of T2B while putting something between the feet like a towel, knee sleeve, or folded pice of paper! Does your technique hold up under fatigue?