These leisurely pursuits have their place, but there’s no substitute for the intensity of intervals and strength training or plyometrics. “When you reduce your intensity, athletic performance declines,” he says. “Cardiovascular fitness and other physiological metrics drop off.” Bone density suffers, too — particularly in women. In short, when you stop pushing yourself, you’ll become less fit, less healthy.
Overweight children who participate in physical exercise experience greater loss of body fat and increased cardiovascular fitness. According to the Centers for Disease Control and Prevention in the United States, children and adolescents should do 60 minutes or more of physical activity each day. Implementing physical exercise in the school system and ensuring an environment in which children can reduce barriers to maintain a healthy lifestyle is essential.
Chronic stress and the subsequent chronic peripheral glucocorticoid secretion plays an important role in the desensitisation of higher brain centre response during acute stressors because it has been shown that in acute (and also chronic) immobilisation, the responsiveness of hypothalamic corticotrophin-releasing hormone (CRH) neurons rapidly falls.26 These adaptation mechanisms could be the consequence of changes in neurotransmitter release, depletion of CRH and/or desensitisation of hypothalamic hormonal release to afferent neurotransmitter input.26 Indeed, concentrations of CRH are elevated, the number of CRH-secreting neurons in the limbic brain regions is increased and the number of CRH binding sites in the frontal cortex is reduced secondary to increased CRH concentrations following chronic stress.25
In line with Martin and colleagues  we found that women more often engaged in walking, swimming and dancing compared to men, while men more often performed jogging, cycling and winter sports. Our data also showed that men performed a higher amount of sessions with domestic activities and combined endurance and resistance training compared to women. The sex differences were the same in both training groups, indicating that disparities in type of exercise between older women and men are independent of the exercise intensity they are instructed to perform.
Evidence from HIIT studies conducted under controlled laboratory conditions has provided proof-of-concept of efficacy . However, it has been argued that HIIT has high efficacy but low effectiveness , and long-term exercise interventions carried out under free-living conditions have been asked for to investigate whether HIIT is feasible as a public health initiative among older adults [9, 16]. Our data showed that both training groups reported on average more than two exercise sessions per week throughout the year. Approximately 60% of the sessions in the HIIT group were performed with a self-reported high-intensity (≥15 Borg scale), indicating that older adults are able to perform HIIT over a long time-period without strict supervision. However, women had a lower proportion of sessions with high-intensity exercise compared to men. This result is in line with previous findings that women (aged 60–67 years) are less likely than men to prefer vigorous physical activity .
If the phrase "3 to 4 reps at 10/5 cadence" is meaningless to you, this book may be also. If the phrase is familiar to you, you probably will already know most of what is written here. It is only to those for whom the phrase is both meaningful and interesting and to those who, in addition, are tolerant of an awkward writing style, that I would recommend the book. Even then, you might enjoy Ellington Darden more.