Increased serum parathyroid hormone (PTH) during moderate-intensity exercise has been reported, suggesting that such exercise may stimulate bone resorption. This study was undertaken to observe the effects of exhausting high-intensity intermittent exercise (HIIE) on serum PTH and on blood parameters that may affect PTH secretion during exercise. Seven young trained adults exercised on 2 days after overnight fasting. On the HIIE day, they performed 6–7 exhausting bouts of 20-sec bicycle exercise (intensity, 170% VO₂max) with intervening 10-sec rests. On the moderate-intensity exercise (MIE) day, the subjects biked for 60 min at 70% VO₂max. The peak lactate concentration in blood after the HIIE was 15.2 ± 1.3 mmol/l. The blood lactate concentration at the end of the MIE was 2.2 ± 0.9 mmol/l. The HIIE significantly reduced the serum PTH (Pre: 30 ± 5 pg/ml, 10 min post-HIIE: 22 ± 4 pg/ml, p < 0.05), whereas the MIE significantly elevated the serum PTH. The HIIE induced a significant increase in serum ionized Ca (iCa); but MIE did not affect iCa. The serum cortisol concentration post-MIE was significantly higher than that observed pre-exercise; no changes from the pre-exercise value were noted post-HIIE. The serum phosphate concentration immediately post-HIIE increased significantly to the same level as that post-MIE. No changes in serum C-terminal telopeptide of Type I collagen (a marker of bone resorption) was observed after the HIIE or MIE. Although these results do not identify stimulator(s) for PTH secretion during HIIE and MIE, they indicate that HIIE does not induce an exercise-induced increase in PTH (which might deteriorate bone metabolism).

Facing the rapid growth in the elderly population worldwide, the need for exercise prescriptions according to individual physical fitness has become increasingly apparent. Despite this, the training system broadly available has not been developed. Accordingly, we have developed a system with internet of things (IoT) for middle-aged and older people called “e-Health Promotion System”, based on interval walking training (IWT). IWT is a training regimen repeating 5 sets of fast walking at more than 70% peak aerobic capacity (VO_2peak) and slow walking at ~40% VO_2peak for 3 min each per day. The system is composed of a device that is equipped with a tri-axial accelerometer and a barometer, and connected to a central server. The sever has a program for storing walking records transferred from the device through the internet, as well as for instructing participants regarding IWT in a feedback manner based on the server database. Using this system, we examined the effects of 5-month IWT in more than 8,700 middle-aged and older people, and found that the training increased VO_2peak by 15%, improved lifestyle-related disease symptoms by 20%, and reduced healthcare costs by ~20% on average. We subsequently reported that the effects of IWT depended only on average fast walking time, rather than average slow or total walking time per week. Recently, we also developed a mobile application program to provide participants with this service on their smartphone so that we can examine the effects of IWT in a much larger population of people at the same time and across generations. The system has great potential to increase interdisciplinary studies between sports sciences and other fields of science to establish and promote a society for health and longevity.

An astronaut’s maximal oxygen intake (VO_2max), along with cardiac function, decreases during space life; and many astronauts experience unhealthy weight loss due to energy imbalances. In fact, excessive exercise may promote an energy deficit. Moreover, a typical scheduled exercise program (2.5 hours per day) appears to be excessive for time-pressed astronauts. Hence, more efficient exercise programs need to be developed for future space missions. With this background, the study of “high-intensity interval aerobic exercise training (HIAT)” was initiated. The HIAT protocol in our study consisted of 3 sets of 3-min high-intensity cycling with 2-min active rest between sets. Two intervention studies conducted with sedentary male adults revealed that VO_2max improvement by HIAT was significantly higher than improvement by moderate-intensity continuous aerobic training (MICT); and that cardiac function significantly improved in HIAT, but not in MICT, even though the exercise duration and volume of HIAT (15 mins, 180 kcal) were substantially lower than those of MICT (42 mins, 360 kcal). Further studies on general workers with metabolic syndrome also showed the superior effect of HIAT to MICT on VO_2max. Studies conducted on astronaut health may provide clues to solving lifestyle-related public health issues because the microgravity environment is similar to physical inactivity in reducing the load on the heart. Lack of time is a significant barrier to exercise habituation in our time-pressed society. Therefore, time-efficient exercise may contribute to the prevention of health risks not only in astronauts, but also in working adults in a modern society with time constraints and sedentary lifestyles.

High-intensity interval training (HIIT) research has drastically increased globally in the last decade. This might be owing to the application of HIIT in various fields such as among cardiovascular disease and cancer populations, and its increasing popularity in the media and fitness industries. It is crucial to realize the substantial benefits of HIIT, keeping safety in mind, for these target groups. In this narrative review, HIIT is discussed from multifaceted perspectives. First, I describe the rationale behind the improvement in aerobic and metabolic capacity with HIIT requiring less time compared to moderate-intensity continuous training, as well as the enjoyable and affective factors and the broad applicability of HIIT due to the “relative” high-intensity training. Second, I describe ways to maximize the effects of HIIT, which include optimising a potential genetic factor in HIIT responder, decreasing non-responders by attaining a targeted intensity, and adhering to the exercise intensity and unsupervised long-term participation. Recent development of HIIT/sprint interval training protocols and several unique clinical studies in the world have helped overcome the barriers against high adherence. Finally, safety and potential risks were only discussed briefly due to insufficient available data. In conclusion, to utilise the benefits of HIIT effectively and safely for unfit subjects with lifestyle-related and chronic diseases, optimising HIIT protocols to include high adherence to exercise intensity and long-term participation should be considered.

It is tragic and ironic, as we speak of the pandemic of physical inactivity, that we already know the cure for physical inactivity, the 4^th leading risk factor for mortality costing billions of dollars in medically related costs and losses in productivity. The solution is simple. People must move more often. And of exceptional relevance, physical activity can prevent diseases which increase the population’s susceptibility to the new coronavirus pandemic, COVID-19. Creating innovative programs which encourage movement is a beginning, but these programs must be sustainable and accessible to a country’s vulnerable populations. 3 WINS Fitness is a free scalable and innovative community-based exercise program serving over 300 participants requiring no external funding for daily operations due to its implementation by university kinesiology students. If we apply our knowledge and work together in significant collaborations, millions of lives can be saved. Population physical activity has not increased since the late 1990’s. We must take a fresh look at identifying new or unique collaboratives and re-inventing current systems. At the core is the education system of university kinesiology/exercise science programs, teaching students the complete landscape of what is required for increases in population physical activity. The Call to Action (CTA) is kinesiology/exercise science departments around the world vigorously taking on the challenge and owning the responsibility for increasing population physical activity. The students of today can control the health destiny of millions of people around the world. The first steps to these departments taking the lead must begin today.