Marilyn Cooper, Low Tiger posture in Stern Grove, 2009 Photo provided
Tai chi is good for everyone, young, old and middle aged, male and female, but has special relevance for people over fifty. After the late twenties, the peak age for recreational and professional athletic performance, reflexes become slower and tissue becomes less resilient. While the mind and spirit can continue to develop, our physical bodies have reached their prime and now need to start to conserve rather than just continue to expend.
Pain, fatigue, and longer recovery time are indicators that it is time to learn tai chi. Tai chi puts you "in the zone" without pounding and straining. It increases circulation, energy, longevity, positive thinking, balance, immunity, co-ordination, bone density, flexibility, and when taught properly, provides protection from injurious assault.
Like its grandmother art - qigong -- tai chi's primary function is qi cultivation. The word cultivation describes the way tai chi and qigong practitioners work - methodically, and in accordance with nature -- like the farmer who stores seed, prepares the soil, and rotates crops to preserve sustainability.
Qi is loosely defined as energy, or "the life force that animates all matter." When qi is cultivated, it flows. When it is blocked, it stagnates, like a pool of water with no fresh, incoming source and no drainage. While tai chi cannot replace a need for emergency surgery or psychotherapy, it can provide self-healing factors that reduce physical and/or mental trauma, and speed up recovery if surgery is necessary.
The mind leads the "qi" and blood follows qi. The increased circulation comes from the slowness combined with the sinking of the weight. The growth is from the bottom up, like a building, or like a tree, ring-by-ring, making it rooted, reliable and long lasting.
Once learned, tai chi is fun to practice, and safer than other types of exercise. Like driving on an icy road, if you go slowly, nothing too bad can happen. Tai chi's positive side effects are often unexpected, such as the letting go of old issues. This is from relaxing, opening the channels, and allowing the energy to flow.
Imagine sinking into a warm bubble-bath, and letting go of all your stress. This is a part of the state you are in while doing tai chi or qigong, except you are fully clothed, standing up and immersed in air, not water. Relaxation is one essential component, but it is the nature of tai chi movement that gives you energy and inner strength - centered, grounded and rooted.
Practitioners enjoy richer, wiser lives from taking the time to learn and practice tai chi. The ease of execution comes from focusing on where you are coming from to get to where you are going, not from trying to be where you are not. You always have to be firmly sunk and rooted on the back leg to achieve the light step on the other leg to advance to the next movement. You can never get ahead of yourself, literally and figuratively.
Ironically, you won't get where you want to be - healthy, calm and youthful - by straining to be as strong as you think you should be, or struggling look as young as you once did. You will achieve this by practicing something that is designed specifically to produce youth and vitality - tai chi.
Pain, fatigue, and longer recovery time are indicators that it is time to learn tai chi. Tai chi puts you "in the zone" without pounding and straining. It increases circulation, energy, longevity, positive thinking, balance, immunity, co-ordination, bone density, flexibility, and when taught properly, provides protection from injurious assault. 
Lamorinda Weekly, Moraga CA