This type of meditation is done with a level of mental focus, on the body's internal landscape, one popular type is designed to encourage the promotion and circulation of energy (Qi) around the body. It can be done in either sitting or standing / walking posture. The first level of this training is known as the Micro Cosmic orbit. This involves using the focused mind to promote the accumulation and then circulation of Qi up the central meridian of the spine and then down the central meridian of the front of the body. If you have read about Dao Yin elsewhere on the site you will realise that the aspect of meditation is closely linked to Dao Yin, very much the mind's Yang to the body's Yin.
This aspect of Dao Yin / Meditation is similar to Kriya Yoga.
Once the above has been carried out successfully for a period of time it evolves into the Macro Cosmic orbit, this involves Qi extending its circulation throughout the rest of the body to the extremities.
A specific area within the area of energy circulation work is Paired Cultivation often referred to as sexual yoga.This aspect of inner development is close to the tradition of Tantra. The idea of the training is to use the balancing sexual energy of a partner to boost and balance your own energy. See the sexual yoga page for more on this.
A very common factor in those schools that went for the purely Clarity and Stillness approach is that they tended to be monastic in nature and as such lent themselves to that type of study and often had many young trainees. It was thought that young people in such an environment had fewer, real world distraction to deal with and as such their minds were more easily trained.
Conversely the Vitality / Energy first schools tended to be lay movements, of a more informal nature with older practitioners. These people had to function in the normal day to day world with everyday problems to cope with such as work and family commitments.
It is thought that a more gradual training approach, using Dao Yin body energetics, that helped the body restore itself energetically and trained the mind in the process was more appropriate.
It is this latter approach I take, both for myself and my students. We have to live in the real world!