Recent research suggests that engaging in more vigorous intensity exercise can lead to greater improvements in VO2 max and eliminate non-response in some individuals. Evidence has shown that roughly 40 percent of people don’t see a measurable improvement in their VO2 max with moderate intensity continuous exercise. However, non-response was eliminated in a group that engaged in a more vigorous manner. Therefore, different strategies can be engaged in successfully based on individual preferences.
Interval training has gained popularity in the last decade. It is a form of training that involves high intensity followed by a period of lower intensity. This can be beneficial for individuals who are time-constrained. Research suggests that high intensity interval training can lead to significant improvements in VO2 max. It is not necessary to commit to three to four hours of zone two training per week to see improvements in VO2 max. In fact, higher intensity exercise may lead to even greater improvements.
Evidence has shown that moderate intensity continuous exercise, even for six months, may not result in a measurable improvement in VO2 max for roughly 40 percent of people. However, engaging in more vigorous exercise seems to eliminate some of the non-response.
VO2 max is the maximum rate of oxygen uptake by the body and is determined by various physiological factors. It reflects the peak integrated capacity of the cardiovascular, respiratory, blood, and skeletal muscle system to take up and utilize oxygen. Having a higher VO2 max is important for athletes and is associated with a reduction in all-cause mortality and the development of chronic diseases.
A study published in JAMA in 2018 showed an inverse relationship between VO2 max and all-cause mortality, with elite performers experiencing an 80 percent reduction in mortality compared to the lowest performers. This highlights the importance of measuring VO2 max for overall health and longevity.
Engaging in physical activity or exercise for general health is different from the training regimen of an elite endurance athlete. Elite athletes engage in 15-20 sessions of training per week, totaling 25-30 hours. The ideal training ratio for optimizing endurance performance is 80% low to moderate intensity training and 20% high intensity training, including interval training. For individuals engaging in 1-4 hours of physical activity per week, the training ratio can change substantially. Engaging in more vigorous intensity exercise may further boost fitness, even with just 1-1.5 hours per week.
Improvements in VO2 max are essential for athletes and committed exercisers. The goal is to optimize the time spent on physical activity to promote overall health. Engaging in more vigorous intensity exercise may potentiate gains, particularly for individuals with low to moderate activity levels. The greatest benefits are seen in those who move from low to moderate levels of physical activity. Elite athletes, on the other hand, focus on maximizing their physiology to eke out even the smallest gains. For average individuals and serious exercisers primarily interested in health, this extreme approach is unnecessary. High intensity interval training is a method that has been shown to increase VO2 max.
Calculating maximum heart rate can be done using the common equation of 220 minus age, but this method does not consider individual fitness levels. There are other scientifically proposed formulas, but there is significant variability in the results. On average, the maximal heart rate for a 40-year-old would be 180 (220 minus 40), but there is a standard deviation of around 10 beats per minute. This means that two-thirds of individuals would fall between 170 and 190 bpm, with 95 percent falling between 160 and 200 bpm. Individual measurement is more accurate than using the standard equation. One way to measure maximum heart rate is to push oneself to the limit with intense exercise, such as running a 400 meter loop as fast as possible or increasing intensity on a stationary bike until exhaustion. Directly measuring maximum heart rate is always better than using standard calculations. A stress test is also a method used to push the body to its limits to measure maximum heart rate.
The World Fitness Level calculator is a valid tool for estimating VO2 max based on research conducted at the Norwegian Technological University. It can provide a reasonable estimate of VO2 max based on age, sex, and activity levels. While it’s just an estimate, it can still be used to track changes over time and assess the effectiveness of a training program. This can help individuals monitor their progress and make adjustments to their fitness routine.
Measuring physiological features such as resting heart rate, max heart rate, BMI, waist-hip ratio, and waist circumference can provide valuable information. Sub-maximal exercise tests, such as the shuttle run test or beep test, can accurately measure VO2 max. These tests provide data on heart rate, power outputs, and lactate levels, allowing for a more comprehensive understanding of cardiorespiratory adaptations. The gold standard for measuring VO2 max is through an accredited laboratory, providing direct and accurate results. High-intensity interval training can have a significant impact on physiological factors such as stroke volume and cardiac output.
The primary factor that separates individuals in terms of their VO2 max is their cardiac output. Maximal cardiac outputs are somewhere around 15 to 20 liters per minute in untrained and moderately trained individuals. Elite athletes have maximal cardiac outputs of 40 liters per minute. Maximal cardiac output is determined by heart rate and stroke volume. The delivery side, primarily determined by the heart, is generally more important than the utilization side in terms of oxygen that limits VO2 max. VO2 max is a good predictor of things like all-cause mortality and cardiovascular disease mortality. High intensity interval training can improve cardiac output. VO2 max is easy to measure and is a relatively non-invasive measure.
The measurement of cardiac output and stroke volume is a highly specialized and invasive procedure. There are limited direct measures of these parameters, but non-invasive methods have been developed. Studies have shown that high-intensity exercise may lead to greater improvements in stroke volume and cardiac output compared to moderate-intensity training. The duration and intensity of exercise play a crucial role in these improvements.
The nuances of exercise training studies make it challenging to provide clear-cut recommendations. Most studies are relatively short-term, so the maximum potential for VO2 max in individuals is not well-understood. Engaging in longer periods of continuous moderate training may lead to similar improvements as high-intensity interval training, but at a slower rate.
Mitochondria play a critical role in skeletal muscle adaptations to exercise. High-intensity interval training has been shown to be a potent stimulus for mitochondrial biogenesis, leading to the generation of new mitochondria in muscle cells.
Mitochondrial biogenesis is a complex process that involves the growth of new mitochondria in the body. Mitochondria form a reticular network within skeletal muscle fibers, and their size and capacity can change rapidly in response to exercise.
Exercise is a stress on the body, leading to changes in ATP levels, calcium, reactive oxygen species, and other compounds. These changes act as signals for the growth of new mitochondria, a process known as mitochondrial biogenesis.
Both high-intensity interval training (HIIT) and continuous exercise have been studied in relation to mitochondrial biogenesis. However, these studies often require invasive muscle biopsies and provide only snapshots of mitochondrial changes over time. Despite this, it is clear that both forms of exercise can lead to measurable increases in mitochondria within days or weeks.
Several studies have compared continuous and interval training, showing evidence that higher intensity exercise leads to a more rapid or larger increase in mitochondrial content over the short term. Mitochondria are the primary place where fat is oxidized to produce energy, and mitochondrial content largely determines fat oxidation during exercise. With training, increasing the levels of the enzyme carnitine palmitoyltransferase (cpt) is important for increasing fat oxidation capacity. Athletes, in particular, aim to have a high rate of fatty acid oxidation to preserve carbohydrate for when it is needed, such as during racing. There is ongoing debate about the best way to increase mitochondrial content and fat oxidation capacity.
Interval training sessions that raise heart rate above 80% of maximum can lead to reaching the lactate threshold, resulting in increased production of lactate. While fat may not be burned during this phase, the increase in mitochondrial biogenesis can lead to greater fat oxidation capacity later on. The increase in mitochondrial content in muscle is critical for enhancing fat and carbohydrate oxidation capacity. Short, intensive types of exercise can stimulate the increase in mitochondrial content. Hormones such as norepinephrine and epinephrine are involved in signaling adipose tissue to break down triglycerides and release fatty acids into the bloodstream. While supplements can increase lipolysis, the limit for fat oxidation resides inside the muscle at the level of the cpt enzyme, which acts as a gatekeeper for fatty acids to enter the mitochondria for oxidation. Mitochondrial biogenesis can increase the cpt enzyme, enhancing fat oxidation capacity.
Mitochondrial biogenesis is a crucial factor for mitochondrial health. The clearance of damaged mitochondria, known as mitophagy, is also important. Evidence suggests that high-intensity exercise is more potent for stimulating autophagy in skeletal muscle than fasting alone. However, some studies have shown that very vigorous exercise can temporarily impair mitochondrial capacity. Overall, exercise is beneficial for the routine maintenance and turnover of cellular processes, including mitochondria. The idea that exercise is a stressor that disrupts cellular processes, leading to recovery and improvement over time, is well-supported. However, it is possible to acutely overtrain and cause disruptions that take a prolonged period of time to recover from.
Eccentric weightlifting exercises are known to be more damaging to tissues and can result in more soreness, requiring additional recovery time. The Wingate test involves intense and demanding exercise on a specialized bike, with high workloads and variable intensity efforts. This test is challenging, uncomfortable, and not considered a fun way to train. In terms of muscle adaptations, increased capillary density and mitochondrial network expansion are crucial for aerobic conditioning. Other adaptations include increased muscle glycogen content and improved transport for various substances, making exercise a therapeutic option for high blood pressure.
Increasing glucose transport capacity on the cell membrane allows for more glucose to be moved into the muscle and stored as muscle glycogen, helping to lower blood sugar levels, especially if they are chronically high.
Engaging in an exercise program can lead to a reduction in diabetic medication, as the muscles become more fit and naturally clear the glucose from the bloodstream.
While high intensity exercise can cause changes in glucose transporters, there is not enough evidence to definitively say whether it is better than moderate exercise. Randomized clinical trials are needed to properly investigate these questions.
Exercise increases insulin sensitivity, with some evidence suggesting that high intensity exercise may lead to greater improvements. However, the underlying studies are relatively small and subject to potential bias.
The research suggests that vigorous intensity exercise may lead to superior benefits. One area of interest is the concept of exercise snacks – brief bouts of vigorous intensity exercise spread throughout the day. Two randomized controlled studies are currently being conducted to measure insulin sensitivity and blood glucose control in participants engaging in exercise snacks. The intervention involves prompts delivered to participants’ cell phones, encouraging them to engage in vigorous intensity exercise four or five times a day. The studies also include a control group engaging in movement snacks, focusing on stretching and mobility exercises. The key variable being measured is the intensity of the movements. Continuous glucose monitoring and accelerometers are being used to track movement and measure outcomes.
VILPA, or vigorous intermittent lifestyle physical activity, is a non-exercise equivalent of an exercise snack. It involves embedding vigorous effort into daily activities, such as taking the stairs instead of the elevator or walking at a vigorous pace. Studies have shown that engaging in VILPA may have meaningful health benefits, including reducing the risk of cardiovascular disease and mortality. Research, such as the UK Biobank study, has provided evidence for the potential impact of VILPA on health outcomes.
Research has shown that engaging in just three to four minutes of Vilpa-like activity per day can lead to substantial reductions in all-cause mortality risks, by 25-30 percent. This suggests that even brief, non-exercise, vigorous intermittent physical activity can have a positive impact on health outcomes. Observational evidence over time has shown that these reductions in mortality risks are robust and compelling.
In fact, some individuals who engaged in more vigorous activity saw even greater reductions in cardiovascular and cancer-related mortality. This is particularly significant as these individuals self-identified as non-exercisers, showing that even those with low physical capacity can still benefit from this type of activity. The same protective effects were seen in individuals who identified as regular exercisers.
The implications of these findings are significant, as accumulating just three or four minutes of Vilpa-like activity per day is equivalent to about 30 minutes of vigorous activity per week. This is very doable and can lead to large reductions in mortality risk. Encouraging the incorporation of Vilpa-like activities into daily routines, such as through wearable technology or apps, could have a significant impact on public health.
Vilpa studies and exercise snacks are related to reducing sedentary behavior. Both may have a double benefit by breaking up prolonged periods of sedentary behavior. Prolonged sedentary behavior increases the risk of ill health outcomes, even for committed exercisers. Individual variation plays a role in how high intensity interval training affects the recruitment of muscle fibers. There are two main types of muscle fibers, slow twitch and fast twitch, based on how quickly the muscle fibers can contract.
There are two types of muscle fibers: slow-twitch (type 1) and fast-twitch (type 2). Slow-twitch fibers generate less force and are resistant to fatigue, while fast-twitch fibers produce more powerful movements but fatigue quickly. These differences are based on the oxidative capacity and diameter of the muscle fibers. Slow-twitch fibers are recruited first for low to moderate force activities, while fast-twitch fibers are called upon for explosive movements. However, the recruitment of muscle fibers is not as clean-cut as previously thought, and studying muscle fibers is a complex and time-consuming process. There is limited data available, mostly from animal studies, making it challenging to draw definitive conclusions.
Muscle fiber types differ between individuals, with some having almost entirely fast twitch or slow twitch muscles. Elite endurance athletes tend to have a higher percentage of slow twitch muscle fibers, while elite strength athletes have more fast twitch fibers. The majority of people have a mix of both types. As people age, there is evidence to suggest a progressive loss of fast twitch muscle fibers, which is why strength training becomes important to maintain muscle viability. Maintaining fast twitch muscle fibers through strength training can help prevent falls and other risks associated with aging. High intensity interval training has metabolic benefits, increasing insulin sensitivity and glucose transport, which is beneficial for both individuals with type 2 diabetes and those looking to prevent it. From elite athletes to sedentary individuals, the spectrum of activity and risk varies, but the importance of maintaining muscle health remains consistent.
High intensity interval training can be used to aid in weight loss and body composition changes. Studies have shown measurable changes in fat mass and lean mass with high intensity interval training, although the differences tend to be relatively subtle. It is possible to achieve the same results with less total exercise or a lower time commitment through vigorous intensity exercise.
There is a small but significant afterburn effect from high intensity interval training, resulting in a heightened rate of metabolism and calorie burning during recovery. This, combined with the time efficiency aspect, makes high intensity interval training an effective method for weight management.
In addition to its physical benefits, high intensity interval training has global effects on the brain, as observed in various studies. These brain effects contribute to the overall effectiveness of high intensity interval training as a method for weight management and fitness.
Recent research has suggested that high intensity interval training may have unique benefits on the brain. The lactate shuttle theory, once considered a metabolic waste product, has been found to be an important fuel for various organs, including the brain. Studies have shown that lactate can be produced under fully aerobic conditions in skeletal muscle and can be circulated to other areas of the body, including the brain. This cell to cell or inter-organ lactate exchange has been well established. Further research is being conducted to explore the role of intensity in physical activity and brain health.
Recent research has shown a potential link between lactate and BDNF levels in the brain. Higher intensity workouts seem to be associated with increased BDNF levels. Lactate has been found to increase BDNF levels when infused into humans, and this is of particular interest for individuals concerned about brain health. Studies have shown that executive function is improved after high intensity exercise, and this improvement specifically correlates with lactate levels. This area of research is growing, and further collaboration with experts at McMaster University could be beneficial.
The effects of exercise on the body and brain are an emerging field of study. Shear force and blood flow have been found to have significant impacts on VEGF and BDNF levels at the blood-brain barrier. The dose response to exercise is a key factor in the increase of lactate, which has been linked to brain health and cancer. Research suggests that high intensity exercise may disrupt and kill cancer cells due to the increased mechanical forces, in a dose-dependent manner. This indicates that exercise has a significant impact on overall health and disease prevention.
The impact of interval training on the brain’s blood flow is a significant area of interest in the field of exercise science. This is a differentiating factor from continuous, moderate exercise. While there is still much to learn in this emerging field, it is clear that there is a unique effect on the brain from intense interval training.
Vascular stress is also a key area of study, particularly as it relates to endothelial function and blood flow to the muscles. The release of certain factors during exercise can promote capillary growth, leading to improved muscle function.
Lactate levels are another important consideration in exercise science. It is important to recognize that individual biological traits can impact an individual’s ability to reach high lactate levels. Continuous monitoring of lactate levels is an area of interest, but current methods rely on occasional finger prick sampling and may not provide consistent results.
The evolution of continuous glucose monitoring provides a potential model for the future of lactate monitoring. Real-time monitoring of blood glucose levels has led to significant advancements in diabetes management, and a similar approach to lactate monitoring may hold promise in the future.
Continuous lactate monitoring for athletes during training and racing could have tremendous value. Monitoring venous levels does not provide information about rates of production and utilization. High blood lactates are commonly seen as bad, but it could also indicate that more lactate is being transported out of the muscle into the blood, which might actually be a good thing from an exercise capacity standpoint. Continuous lactate monitoring could provide valuable insights into metabolic stress during exercise.
The movement of lactate to the bloodstream can help protect muscles. It’s important to challenge the thought process around lactate and its impact on muscle fatigue. High-intensity training can increase lactate transporters, which can help remove lactate from muscles. Lactic acid rapidly dissociates into lactate and protons, impacting contractile processes and enzymes. While lactate may not directly cause fatigue, it is still a valuable measure and can be a good proxy for metabolic activity. Zone 2 training can benefit from understanding the role of lactate. High-intensity training uses muscle glycogen and impacts aerobic and anaerobic capacity.
Anaerobic capacity is a crucial component for athletes who engage in high-intensity, short duration activities. The Wingate test is widely accepted as the best measure of anaerobic capacity, as it quantifies power output in terms of wattage during an all-out 30-second effort. This test allows for the measurement of peak power output, which can reach high levels, even up to 1500 watts for elite power athletes.
Exercising at 300 percent of VO2 max pace is possible through power outputs above the VO2 max power output. Short, hard efforts can exceed VO2 max power, resembling the intensity of a sprint from danger pace. This pace reflects the maximum effort an individual can sustain for a short duration, similar to fleeing a burning building or saving a child from an oncoming car.
In comparison, sprint interval training and the Wingate test focus on high power outputs, but the sprint from danger pace represents a specific, intense effort that goes beyond VO2 max power output and may only last for a few seconds.
In high-intensity efforts lasting five to ten seconds, the body is able to generate ATP non-oxidatively at the highest work rate. This type of sprinting from danger pace can be important for discriminating fine changes that could further support an athlete’s performance.
There may be benefits in changing training protocols to incorporate sprinting for VO2 max benefits. Varying up training, just like spreading out investments, might be the best approach for individuals.
Engaging in short, sharp, hard efforts can be beneficial, as recent evidence suggests renewed interest in elite endurance athletes incorporating sprinting in their training. Studies have shown that highly trained elite cyclists can benefit from effort-matched 30-second sprints in comparison to traditional high-intensity interval training for five-minute repeats.
The incorporation of sprints resulted in a boost to performance in a 20-minute time trial, along with a small but significant improvement in vo2 max. This suggests that there may be a place for athletes to include repeated sprint training to enhance their performance. Incorporating vigorous effort can be beneficial for general fitness, although some individuals may not be suitable for sprinting, especially when starting out.
It is suggested that longer intervals at a slightly lower intensity should be incorporated into the training regimen, rather than exclusively focusing on tabata-style training. Modality-specific training, such as on a bike, should be considered before exploring different modes of training.
Overall, varying the approach to training may be the best for general fitness and performance improvement.
It is recommended to incorporate longer intervals of three to five minutes at the highest sustainable intensity in order to maximize gains in vo2 max. This style of interval training should be done four times, which will likely require a 20-minute commitment. It is important to not maintain high intensity during the 10-second recovery periods and to incorporate some resistance training on alternate days.
The metabolic challenge of longer intervals is different from shorter, repeated intervals, and it is important to challenge the metabolic system in different ways. Total volume of training is also an important variable to consider. Incorporating three to five minute intervals with warm-up, cooldown, and recovery periods in between can provide a 15-minute intense workout. It is essential to push as hard as possible during these intervals to maximize power outputs.
Research has shown that varying the duration and intensity of interval training can produce significant improvements in cardiorespiratory fitness. Studies have demonstrated that both 10-minute and 5-minute interval protocols can yield positive results. For individuals with time constraints, shorter intervals may be a viable option. Additionally, optimizing interval training for VO2 max while being time-efficient is a goal for many individuals. There is a strong correlation between VO2 max and brain health, as well as cardiovascular health.
The initial studies in this area used the Wingate test, which involved 30-second intervals. However, it was found that the last 10-15 seconds of the Wingate test were the most impactful. This led to the development of a protocol that involved 3 22-second intervals with a total workout time of 10 minutes.
This approach is known as the one-minute workout, and it is designed to be time-efficient while still providing the benefits of vigorous exercise. Other researchers have also explored variations on this theme, such as reduced exertion high intensity training, which involves 10-20 second efforts in a 10-minute workout.
Numerous studies have been conducted to demonstrate the effectiveness of these short, intense workouts in improving various health outcomes.
Recent studies have shown that interval training can improve fitness to a similar extent as traditional continuous training, in a fraction of the time. Work-to-rest ratios play a role in the effectiveness of the training. High intensity interval training (HIIT) and sprint interval training (SIT) differ in terms of the intensity of the workouts. SIT involves shorter, higher intensity bursts of exercise, while HIIT is more sub-maximal. Both types of interval training have been shown to be effective in improving fitness.
Research has shown that shorter, intense efforts may not be as uncomfortable as previously thought. Dr. Ed Coyle’s work at the University of Texas at Austin has focused on four-second all-out efforts with short recovery periods. This type of training may not be as associated with feelings of discomfort as traditional high-intensity efforts. The concept of reduced exertion interval training (REHIT) involves adjusting work-to-rest ratios to decrease perceived exertion while still achieving high-intensity training. It is important to consider that perceived exertion may not always accurately reflect the level of effort being exerted during training. This research challenges the notion that all high-intensity training is inherently uncomfortable and may provide new insights into effective training methods.
The disconnect between ratings of perceived effort and heart rate is a notable topic in exercise science. Traditional borg rpe scales are based on a scale of six to twenty, which is correlated with resting heart rate and maximal heart rate. However, in studies of high-intensity, short duration work, there is a clear mismatch between perceived effort and heart rate.
For example, in a study of older individuals with type 2 diabetes, who were doing high power outputs at very high percentages of their maximal heart rate, their average rating of perceived effort was about a seven out of ten, despite their objective exertion.
This raises questions about the accuracy of perceived effort in relation to heart rate, especially in the context of higher intensity, short duration exercise. Further research is needed to better understand and reconcile these discrepancies.
Interval training is an effective way to improve cardiovascular health. Studies have shown that interval walking can be just as effective as continuous steady state walking, especially for individuals with type 2 diabetes. By alternating between periods of higher intensity and lower intensity, individuals can challenge their cardiovascular system and improve their overall fitness level. It’s important to start with a pattern of alternating intensity and then build from there, gradually increasing the level of challenge. This approach is empowering and can be adapted to individuals at different fitness levels. Whether you’re just starting out or already dialed in on your fitness routine, interval training can be a beneficial addition to your workout regimen.
Research shows that adding intervals or varying the pace during walking can lead to greater improvements in cardiorespiratory fitness, body composition, and reduction in 24-hour blood sugar for individuals with type 2 diabetes. This evidence suggests that interval training may provide greater benefits than continuous walking.
It is important to note that interval training comes in many different forms, and numerous studies have shown that individuals with cardiometabolic diseases, cardiovascular disease, heart disease, type 2 diabetes, older individuals, and people with metabolic syndrome can benefit from interval training.
While there is immense debate in the field, research supports the idea that many more people than initially thought can perform and benefit from interval training. The science surrounding high intensity interval training and cardiovascular disease is well-established, with pioneering work dating back to the 70s and 80s. However, different regions may have varying levels of acceptance and recommendation for high intensity interval training.
In Norway, Ulrich Wisloff’s work has been integrated into cardiac rehab training. It is generally accepted and has strong evidence supporting it. However, there are different viewpoints on the risk of vigorous intensity exercise. While it may transiently increase the risk of an event during the exercise, the absolute risk remains relatively low. Engaging in actual exercise, both moderate and vigorous, has low absolute rates of risk. After the event, the relative risk is much lower than for individuals who remain sedentary. It is important to consult a cardiologist before engaging in vigorous intensity exercise, especially for individuals with certain conditions such as atrial fibrillation and unstable angina. An exercise stress test can provide valuable information about one’s ability to engage in exercise.
In scientific studies, individuals with type 2 diabetes undergo a 12 lead ecg stress test before being recruited. Yellow lights indicating potential risks led to participants not being recruited, possibly impacting study outcomes. This raises concerns about the potential risks of inactivity for those not recruited. It is not always a guarantee that exercise clearance from a doctor ensures safety. Sudden adverse events cannot be ruled out, even in younger individuals. Interval training can be beneficial for older, untrained individuals without reaching maximal heart rates. The term “interval training” should be more encompassing to avoid misconceptions about its intensity.
In the 1980s, there was a group in Germany that was conducting interval training in cardiac patients, which was initially met with skepticism. However, it was later discovered that many cardiac patients were already engaging in interval training without realizing it, due to their low exercise capacity. This revelation led to a more empowering message for individuals who may have previously viewed interval training as unattainable. The work to rest ratios of interval training can also be modified to accommodate different fitness levels. High intensity resistance training, which involves very high force efforts that last less than a second, can also be considered a form of interval training. Therefore, interval training can be adapted to suit a wide range of individuals and can play a significant role in improving cardiovascular health.
Interval training can be classified into aerobic, resistance, and body weight styles. It provides a middle ground between strength gains and fitness improvements. Engaging in interval training for 10 to 20 minutes with short recovery periods can keep heart rate up to 80 percent of maximum while increasing functional strength. This style of functional training, similar to CrossFit, can be beneficial in a time-efficient way. The potential for muscle mass gains from high-intensity interval training depends on the individual’s starting level. Those who are relatively fit and healthy may not see significant changes in muscle protein synthesis or fiber size, while deconditioned individuals could see improvements. However, once a certain level of fitness is achieved, interval training may not be a hypertrophy stimulus.
The conversation was focused on various exercise techniques and their impact on muscle growth and overall fitness. The question of whether traditional resistance training or high-intensity functional training is more effective was raised. The importance of balancing cardio respiratory fitness and strength training was also discussed. The idea of a combination of aerobic training and resistance training was brought up, with the possible interference effect being addressed. The evidence suggests that while there may be a slight interference effect, it is not significant enough to negate the benefits of both forms of exercise.
The evidence suggests that both cycling and running can have interference effects if done very close together, but the impact is likely relatively small. For those seeking maximal gains, it may be beneficial to leave a few hours between training sessions. Research has shown that combining aerobic exercise with resistance training may have beneficial effects on blood flow. Meta-analyses of various studies indicate that for most people, it may not be a significant issue if they choose to do both activities in the same day. However, for those looking to maximize their gains, it is ideal to separate the activities by a couple of hours.
When it comes to high-intensity interval training (HIIT), the guidelines for moderate and vigorous intensity aerobic exercise are well-established. However, HIIT is a form of physical activity, not just exercise. For those aiming for general health or elite performance, it may be beneficial to incorporate HIIT into their routine, but specific guidelines for time frames are not as clear.
Physical activity guidelines have not changed much, with the latest guidelines consistent with the World Health Organization’s recommendations of 150 to 300 minutes of moderate or 75 to 150 minutes of vigorous activity per week. Moderate activity is defined as 3 to 5.9 metabolic equivalents or a 5 to 6 on a ten point rating scale, while vigorous activity is above 6 METs or 7-8 on the ten point scale. Engaging in this level of weekly physical activity can lead to substantial health benefits for the brain, muscles, and overall well-being. It is important to note that these guidelines are not meant for elite athletes looking to optimize their performance. The recent change removing the guideline that activity should be accumulated in bouts of at least 10 minutes reflects the recognition that all activity counts and can contribute to health benefits. These guidelines are suggestions for achieving health benefits through physical activity.
Experts tend to be conservative because they want to see more evidence before making definitive recommendations on interval training. Interval training, including HIIT, may already fit within the guidelines for moderate and vigorous activity, but the guidelines may not explicitly mention it. The guidelines may evolve in the future, but for now, more evidence is needed before definitive recommendations can be made. Some studies suggest that even 30 minutes of vigorous-like efforts may be associated with health benefits.
There are some people who may need to do more exercise to achieve the desired results. The guidelines do not address how little exercise one can get away with, but rather encourage people to do more. There is a gap in research when it comes to sex differences in exercise. Post-menopausal women do not need to worry about chronic increases in cortisol levels from interval training. The benefits of exercise are clear and it is hard to argue against its benefits.
Research indicates that there may be subtle sex-based differences in some outcomes, but more research is needed to fully understand the extent of these differences. Ongoing work in this area is looking at sex-based differences in response to specific types of training, with preliminary findings suggesting that individual variability may play a larger role than biological sex. This highlights the need for further research on diversity of responsiveness in order to gain a comprehensive understanding of these differences.
Scientific studies have not incorporated best practices for making systematic comparisons between sexes. It’s important to consider environmental factors, such as sleep and dietary intake of iron, which can affect performance. 20 to 30 percent of menstruating women may be iron deficient without knowing it, impacting their performance. While it’s important to understand potential differences in performance based on menstrual cycle, in the big picture it’s just one more factor contributing to variability. High intensity interval training can impact bone mass and density, depending on the specific mode of exercise. Factors like impact and surface can make a difference in bone health.
Research has shown that individuals with joint injuries, such as meniscal injuries or osteoarthritis, can benefit from remaining active. Cycling is a low-impact exercise that allows for vigorous activity without causing further damage to the joints. High intensity interval training can also be done with activities such as jumping rope, which may actually be beneficial for bone health.
There is a misconception that individuals with heart problems, such as afib or angina, should not engage in high intensity interval training. However, studies have shown that elite athletes, who engage in high intensity training, have a lower risk of cardiovascular-related mortality. It is important to consider the individual’s specific condition and consult with a healthcare professional before starting any exercise program.
Recent reviews have suggested that individuals engaging in very high intensity and volume exercise over a lifetime may be at greater risk for heart issues. While there are theories, a definitive cause and effect hasn’t been established. Extreme exercise may carry some cardiovascular risk, but the evidence doesn’t line up with longevity data.
As for hypoxic training, restricting nasal or mouth breathing during vigorous exercise may compromise performance. It’s not clear if this type of training has significant benefits, and it may not necessarily enhance training responses.
The more interesting area of study is blood flow restricted training, which shows potential for impacting respiratory and diaphragm muscles. However, it’s important to remember that the limitation to VO2 max is generally related to the heart, not the pulmonary system.
Ongoing research shows interesting changes in performance-related metrics and metabolic stresses induced with blood flow restricted training. The future of high-intensity interval training research involves behavioral interventions to encourage physical activity and large-scale randomized clinical trials comparing traditional endurance exercise with interval training. The focus is on optimizing measures of longevity, health, and performance for athletes.
In the field of exercise science, there is a need for larger, collaborative studies with proper sample sizes and power calculations to reduce bias in results. Rigorous research design and multi-center trials are necessary to inform physical activity guidelines. Elite athlete training is currently based on individual experiments, and there is a need for large interventional studies to determine the best training methods. Technological advancements in sleep research and activity tracking have the potential to revolutionize training and everyday activity tracking. The use of activity prompts to encourage behavior change is an area of interest for further study.