I asked Amatsu Sensei regarding solo training in Daito Ryu and he said samurai did not do solo training, they always trained with their teacher. Solo training is a more modern approach developed so that women and children can train.

For example in the Sagawa Dojo (from Merts link) it read 'Aiki Budo is the Way of Human Development', the 'do' makes an important distinction.

In the Tokimune link (from Merts link) it read the following;

- Practice of Daito-ryu Aikibudo : Those who practice the Daito-ryu 'Aikibudo' must learn the 'Aikijujutsu' which is its base.
- Aiki-tanren-ho : It is practiced in couples and when the partner grabs our wrists...

Concerning "internal power," this concept is likewise difficult to strictly define. There are as many definitions of this concept as there are schools claiming to teach it. In TSYR we have a series of kata called "Nairiki no Gyo." These kata seek to cultivate specific body skills associated with developing internal energy. But what exactly are these skills and how are these kata employed to develop internal strength? As part of our gokui, I am not permitted to discuss them in detail outside the kai membership but I can give you a general idea of what they constitute. They are solo exercises that inculcate the proper balance, movement and muscular application utilized in our greater curriculum. These types of exercises are actually quite ubiquitous in Japanese jujutsu schools of the Edo Period, although they are rather unfamiliar to those outside the membership of specific Nihon koryu. According to Yoshin ryu lore, this form of body training was introduced to Japan from China in the mid-Edo Period. In the case of Yoshin ryu, the Nairiki no Gyo were specifically created adaptations of Chinese practices intended to augment the study and application of specific body skills required in Yoshin ryu's greater curriculum.