Exercise physiology research has consistently shown that working out with a high level of intensity is the most efficient way to generate metabolic adaptations so that people can successfully reach their fitness goals of weight control, lower body fat, greater lean muscle mass, and better overall health.  By using a heart rate monitor to measure workout intensity as well as the unique motivational features in the Phyzseek fitness app, people can consistently achieve a high level of intensity to get transformative results. 

What is exercise intensity?

Very simply, exercise intensity refers to the amount of energy used during a workout.  Intensity can be referred to on an absolute or relative basis.  Absolute intensity can be applied to anyone, independent of any other factors.  Relative intensity is specific to the individual and depends on their maximum capability to perform work. 

Absolute intensity is typically measured as a metabolic equivalent or a MET.  1 MET is the amount of energy used by a person at rest.  As the amount of work being done and the intensity of exercise increases, the number of METs rises as well.  For example, running at a 10 minute/mile pace is equivalent to 10.2 METs while running at a 6 minute pace requires 16 METs of work.  The number of calories burned during exercise is directly related to the METs of work performed.

Relative intensity is a better way to measure a person’s workload because it is more specific to an individual’s fitness level.  It accounts for people with different exercise capabilities as measured by a person’s estimated maximum heart rate (HR_max), VO2_max or heart rate reserve (HRR).  Exercise stress causes a person’s body to adapt and generate metabolic transformation.  The higher the intensity, the greater the stress and the larger the adaptation.

How is exercise intensity measured?

Exercise intensity is typically measured as a percentage of a person’s exercise capabilities.  In other words, each person has a maximal ability to perform work based on their fitness level and intensity is measured as some portion of that maximal ability.  A person’s ability to perform work at a high intensity level is related to multiple factors including cardiovascular function and their body’s ability to deal with blood lactate.  The better they are at moving oxygen and nutrients around their body and into cells, the greater their ability to perform work at a high level of intensity.  And, with respect to blood lactate levels, people who produce less lactate during high intensity exercise, and are better at clearing it from their bodies, tend to be able to perform at a higher level of intensity. 

For individuals without access to complicated equipment, heart rate monitoring is the best way to measure workout intensity.  While wearing a heart rate monitor, an individual can track their heart rate, i.e. workload, and increase or decrease their exercise intensity, accordingly.  In general, a person’s maximum heart rate (HR_max) is a function of age and can be estimated as 220 – Age.  In reality though, a person’s HR_max can be 15 – 20 beats higher or lower than the calculated rate.  Intensity can be measured as a percentage of HR_max.  A low level of intensity is less than 50% of HR_max, a moderate level is 50% - 69% of HR_max, and a high level of intensity is 70% - 85% of HR_max.  Near maximal intensity is considered to be above 85% of HR_max. 

Why is exercise intensity so important?

Exercise physiology research has repeatedly demonstrated that as intensity is increased, there is more pronounced adaptation and greater metabolic transformation with resulting health benefits.  While near maximal and supramaximal intensity has been shown to produce the greatest amount of adaptation, there is also an increased risk of potential injury and most people, except for elite athletes, cannot sustain these intensities for any meaningful period of time. 

Therefore, Phyzseek’s SHIFT program targets the optimal level of intensity to achieve the greatest adaptation while still being sustainable.  Importantly, as a person’s fitness level increases, the target intensity must be increased to produce further physiological adaptations. 

Higher Intensity Levels Generate Better Weight Control & Less Body Fat

With respect to weight control and lower body fat, research has consistently shown that the higher the intensity, the greater the results.  There are several reasons that explain this fact.

1. Greater intensity during a workout burns more calories given that caloric expenditure is directly correlated to the amount of work being done. 
2. Increasing intensity, particularly when enhanced with resistance exercises, drives the body towards using a greater amount of anaerobic metabolism (without oxygen), which results in rising blood lactate levels and even more calories being burned during the workout. 
3. EPOC (excess post-exercise oxygen consumption), which occurs for an extended period of time AFTER the workout, can also significantly increase the total calories burned.  As workout intensity increases, EPOC magnitude and duration increases.
4. As intensity increases, glycogen (stored form of glucose, which is crucial for energy production) depletion accelerates.  Since the body prefers not to experience low levels of glucose, it adapts by increasing the amount of fat (as opposed to glucose) that is used for energy.  The obvious effect is to burn more fat thus reducing body fat percentage.

Intensity Level Correlates with Living Longer & Healthier Lives

Research has consistently shown that high intensity exercise is an extremely efficient and effective way to improve VO2_max, which has been shown to be directly correlated with a reduction in all-cause mortality, i.e. living longer lives. 

According to multiple studies, as the intensity increases, the benefit on VO2_max also rises.  In one study done by Gormley, et. al. (2008), subjects were assigned to an intensity group defined as moderate, vigorous, or near-maximal.  Percent VO2_max increases in the near-maximal (+7.2 mL/kg/min = +20.6%), the vigorous (+4.8 mL/kg/min = +14.3%), and the moderate (+3.4 mL/kg/min = +10.0%) groups were all significantly different from each other.

VO2_max is inversely correlated with all-cause death rates.  A very large study done by Kodama, et. al. (2009) showed that cardiorespiratory fitness (maximal aerobic capacity), as measured by METs (VO2_max = 3.5 x METs at maximal aerobic capacity) is a predictor of all-cause mortality and cardiovascular events in healthy men and women.  People with a maximal aerobic capacity of 10.9 METs or more (VO2_max of 38.2 or higher) had substantially lower rates of all-cause mortality and cardiovascular events compared with those with an aerobic capacity of less than 7.9 METs (VO2_max of less than 27.7).  The study showed that for every 1 MET (+3.5 mL/kg/min for VO2_max) increase in maximal aerobic capacity there is a 13% improvement in the risk of all-cause mortality and a 15% improvement in the risk of having a cardiovascular event. 

High Intensity is Required to Increase Growth Hormone Levels

Human growth hormone is directly responsible for the turnover of muscle, bone and collagen, in addition to regulating fat metabolism to maintain a lean body.  Studies have shown that there is an exercise-induced growth hormone response (EIGR).  In addition, studies have demonstrated that an intensity threshold must be reached for the EIGR to occur.  The greatest growth hormone release takes place with an exercise intensity that causes an increase in blood lactate levels for a minimum of 10 minutes.  Therefore, to obtain the benefits of higher growth hormone secretion, a high level of exercise intensity must be reached.

How does Phyzseek help drive user intensity?

Recognizing that higher levels of workout intensity are required to produce fitness results, the Phyzseek app incorporates multiple features to drive intensity including:

1. a color-coded heart rate monitor to ensure the user achieves a targeted intensity level
2. a user-programmed Pacer to drive intensity even when working out alone
3. Health metrics showing intensity level reached
4. Workout result percentile ranks (PhytRank), fitness level scores (PhyzioLevel) and Top 25 leaderboards to drive friendly competition, which also drives individual intensity
5. Social networking to provide accountability to ensure workout consistency & intensity

Color-Coded Heart Monitor Ensures Users Achieve Target Intensity

During a workout, a color-coded heart rate monitor located in the lower right corner of the screen ensures that the user is achieving their target intensity level.  The target intensity level is a function of the person’s age (HR_max) and fitness level (beginner, intermediate, advanced).  The Phyzseek app automatically adjusts target intensity: the beginner target percentage of HR_max is 75%, the intermediate target percentage of HR_max is 80% and the advanced target percentage of HR_max is 85%.  When the target intensity is reached, the color-coded heart monitor turns green.  Within 10% of the target intensity, the monitor will turn orange but remain blue until that point.

Pacer Drives Intensity Even When Working Out Alone

The Pacer is programmed by the user prior to each workout, depending on what results they want to achieve.  The user may want to beat the results they attained the last time they did that workout or they may want to beat a friend’s result.  Once the Pacer is programmed and the workout begins, the Pacer tells the user, throughout the workout, where in the workout they need to be in order to stay on pace to achieve the desired result.  The Pacer is designed to push the user’s intensity as if a personal trainer is standing next to them at all times.

Intensity Health Metrics Show Intensity Achieved

Following each workout, the user will be able to view their intensity level.  They can view their average heart rate, maximum heart rate and calories burned.  But, more uniquely, they can view their Average Intensity and %Intensity.  The Average Intensity measures the average percentage of their heart rate maximum that was achieved while the %Intensity shows the percentage of time that the user spent at or above their target intensity.  Each intensity metric can be compared to the levels achieved by other users to see how their intensity matches up.

Friendly Competition Also Drives Intensity

There are several features that drive friendly competition to further motivate users to achieve a high level of intensity.  Immediately following a workout, through PhytRank, the user can view how their results compare to other users throughout the world on a percentile basis (PhytRank).  They can also see how the recent workout affected their fitness level (PhyzioLevel), including how each workout category (Interval, Lactic Loading and Endurance) contributed to the metric.  And, the Top 25 leaderboard, shows the user with the Top 25 results for each workout, PhyzioLevel, Average Intensity, %Intensity and Calories Burned.

Social Networking Drives Accountability & Intensity

Phyzseek’s social network fosters a cohesive on-line fitness community, which acts to increase accountability and ensures workout consistency & intensity.  As one part of the social network, users have the option to join a PhyzTeam, consisting of eight people with similar fitness capabilities.  As a member of a PhyzTeam, the user can post personal records and will see the workout results from all PhyzTeam members.  Team members can comment on posts to provide congratulatory remarks and support.  The concept behind a PhyzTeam is to create a source of accountability to its members, thus driving consistency and providing a source of motivation to work out with intensity.