Use your arms to generate momentum for completing those situps. Rookies to our methodology tend to leave a lot of fitness on table by folding their arms across their chest, in an attempt to more isolate the abs. We understand why this is. We were all taught to do them this way. It is Old School thinking which persists to this day.
It's not that GPP is against isolation. Our programming is keen to gain the most benefit from ANY valuable movement. Isolated abdominal movements can be extremely valuable to your over-all health. But, they can not be performed to the exclusion of multi-joint abdominal movements. Excluding either of these methods leads to incomplete health gains.
We greatly value the added health benefits to the upper body that swinging the arms during situps affords. Besides adding shape and fitness to the arms and shoulders (in addition to the legs, hips and abdominals), it is also an extremely functional movement. Sitting up by generating momentum from the arms is how you would naturally do this movement - OUTSIDE of the gym.
GPP believes it is important to train your body INSIDE of the gym in the same ways that it functions OUTSIDE. This sadly seems to be a concept long lost upon health & fitness professionals beyond our realm.