Two moves is better than one, right? You may want to do this move on a mat or a towel for padding. Start in a high plank position with core tight. Lower onto both forearms at the same time, maintaining a tight core and level hips. Now push back up onto hands at the same time to return to starting position. Finish by drawing right knee into chest, then left knee into chest, doing a mountain climber.
In summary, if you're only interested in a basic understanding of HIT methodology and where much of it originated I would suggest starting with a far less technical book. I suggest starting with the last published edition of Ellington Darden's "The Nautilus Book" and perhaps "Total Fitness: The Nautilus Way". If you like what you read and want to dig a little deeper into the evolution of HIT read Darden's more recent book, "The New High Intensity Training: The Best Muscle-Building System You've Never Tried". If the gears in your head are in high gear after that and you really want to get DEEP into what evolved from the original Nautilus protocol _then_ you go for "Superslow" or preferably "The Renaissance of Exercise: A Vitruvian Adventure Volume 1". When your grasp of all the aforementioned material is truly solid then move on to Doug McGuff's writing. McGuff's ideas do not surpass or supplant Hutchins' but rather sharpen the points with brilliant thoughts and clinical observations from a medical physician's perspective. Doug McGuff, MD published his "Ultimate Exercise: Bulletin #1" in the late 90's and later updated that with "Body by Science: A Research Based Program to Get the Results You Want in 12 Minutes a Week", both of which are hugely valuable contributions to the literature on HIT methodology and philosophy. His article about "Stoicism in Training" is critical reading.
It is well known that exercise in the older population may prevent several diseases [1–4]. Reduced physical activity impairs the quality of life in elderly people with Alzheimer's Disease , Parkinson's Disease , and Depressive Disorders . Moreover, musculoskeletal, cardiopulmonary, and cerebrovascular decline are associated with poor physical fitness because of the cumulative effects of illness, multiple drug intake, fatigue, and bed rest [7, 8]. The effects of physical activity and exercise programs on fitness and health-related quality of life (HRQOL) in elderly adults have been widely studied by several authors [9–11]. De Vries et al.  conducted a meta-analysis focusing on elderly patients with mobility problems and/or multimorbidity. Eighteen articles describing a wide variety of actions were analyzed. Most used a multicomponent training program focusing on the combination of strength, balance, and endurance training. In 9 of the 18 studies included, interventions were supervised by a physical therapist. Intensity of the intervention was not reported and the duration of the intervention varied from 5 weeks to 18 months. This meta-analysis concluded that, considering quality of life, the exercise versus no-exercise studies found no significant effects. High-intensity exercise appears to be somewhat more effective in improving physical functioning than low-intensity exercise. These positive effects are of great value in the patient population but the most effective type of intervention remains unclear. Brovold et al.  recently examined the effects of high-intensity training versus home-based exercise programs using the Norwegian Ullevaal Model  on a group of over-65-year-olds after discharge from hospital. These authors based their study on the Swedish Friskis-Svettis model  which was designed by Johan Holmsater for patients with coronaropathy to promote their return to work and everyday activities and improve their prognoses. This model includes three intervals of high intensity and two intervals of moderate intensity, each one lasting for 5 to 10 minutes. Included in each is coordination. Exercises consist of simple aerobic dance movements and involve the use of both upper and lower extremities to challenge postural control . Exercise intensity was adjusted using the Borg Rating of Perceived Exertion (RPE) Scale. Moderate intensity was set between 11 and 13, and high intensity was set between 15 and 17 on the Borg Scale.