I have done kung fu exclusively and obsessively for long periods of time because of my fascination with the evolving skill set. However, the times I feel the best physically are when I include cross-training. Otherwise, the knees, back and hips can get stiff and sore, despite the aspect of qi cultivation.
Habitual training in kung fu (or anything) can cause repetitive stress injuries. The knees and hips are strengthened from all the weight sinking that is a requirement of all the systems. Conversely, the knees and hips can tire and become inflamed from the constant stress. Rest can help, but upon returning, the same pain might reoccur. There are lots of good solutions, particularly cross-training.
The Tendon Exchange (Yi Gun Gin) is a fierce and insightful (much like Tamo himself) way to cure joint pain. This form is a fantastic adjunct to any type of exercise – sports, hiking, swimming, biking, because it synchronizes breath with internal movement with zero impact on the joints. Even though kung fu offers a series of systems that can antidote each other, they still all sink the weight and stress the quadriceps. The mind, body and spirit can experience ennui from doing the same old, same old. Changing it up is really advantageous (and fun) and gives your body a completely fresh perspective.
Dance, Yoga, and Pilates (and combinations of all three) are great ways to stay strong and fit, and give the body a break from all the dropping and hollowing. Ballet in particular lifts while kung fu sinks, making it a great way to release tension from the habitual postures of kung fu. Ballet works on the small muscles and ligaments in the feet, ankles and hips much more than kung fu.
Yoga provides deeper stretches to hard to reach areas. Pilates is used as physical therapy for dancers so they can continue to dance into old age by strengthening and stretching the whole body from the core so dance movements are done with more control.
The cross-training videos all are done lying down on a mat. There are no special devices needed – balls, weights, or blocks. If you don’t have a mat, a towel or folded blanket on a non-slippery surface will do just fine. You will feel stronger, taller and more open after the both the Core in Motion and Pilates training. I recommend either or both as a healthy alternative at least once a week.