I believe we are coming around to the conclusion that what was recommended for years by the medical community (30 minutes of "aerobic exercise" 3-5 times a week, getting the heart rate up to 80% max. for age, etc.) has been inadequate, and of too low an intensity level. When an activity is of sufficient intensity, and not of a certain duration or repeated a certain number of times, the body will initiate a total-body response (metabolic, HDL, glucose tolerance, blood pressure, bone mineral density, immune competency, etc.) It appears that if this level of intensity is never reached, regardless of the amount of time spent or the frequency it is repeated, the beneficial response by the body never occurs, or is at least blunted.
Negative Sets. Weight training works with and against gravity. The motion towards the bar in a pull-up is called the "concentric movement," while heading back towards the ground is an "eccentric movement," or the negative portion of the movement. Resisting the pull of gravity during the negative porting of the movement taxes the muscles in a different way Myofibrillar disruption following acute concentric and eccentric resistance exercise in stregth-trained men. Gibala, M.J., Interisano, S.A., Tarnopolsky, M.A., et al. Department of Kinesiology (Neurology and Neurological Rehabilitation), McMaster University, Hamilton, ON, Canada. Canadian Journal of Physiology and Pharmocology. 2000 Aug;78(8):656-61.. At the end of a long set, switch to just performing negatives (with a partner's help on the way up) or work towards getting those difficult bodyweight movements (like a pull up or dip) by only performing the negative of the movement. Sounds easy? Just try it!
Flexibility is a factor in yoga, but it is not a necessary for beginner classes. Continued practice over time will increase your agility and flexibility. You can see positive results over time even if you only attend an hour a week, but attending classes around 2-3 times per week will help you experience the most benefits. Yoga classes usually last around an hour from warm-up to cool down.
Exclusion criteria included major diseases or conditions such as severe heart disease, uncontrolled hypertension, obesity, osteoarticular pathology, and neurological disease. Criteria were evaluated on the basis of clinical history, resting ECG, and physical examination. Participants maintained their lifestyles and were instructed not to take part in any other physical programs throughout the study. At the time of the initial design, the study consisted of a 12-week randomized controlled trial with a frequency of 3 times a week, 36 sessions in all, ending with a new assessment of their wellness and the potential persistence of the results on functional/physical capacities.