Unless you know how to lunge correctly, supplying an outside rein and ensuring his hind legs are really working, lunging won't do much.
If you have hills, get on him and walk him up and down a hill for around 20mins a day and slowly increase it.
Any reason why he 'wont' trot or canter, is there anything medically wrong with him to prevent him doing so or is he just being a horror head and refusing to do so?? If he's just misbehaving, get an instructor to help you out with him because he will build muscle much more quickly and effectively if you are able to trot and canter him under saddle.
If you have hills, get on him and walk him up and down a hill for around 20mins a day and slowly increase it.
Any reason why he 'wont' trot or canter, is there anything medically wrong with him to prevent him doing so or is he just being a horror head and refusing to do so?? If he's just misbehaving, get an instructor to help you out with him because he will build muscle much more quickly and effectively if you are able to trot and canter him under saddle.