Cardiorespiratory Fitness Prescriptions for Improving V̇O2 max in Naturopathic Medicine

Protocols in naturopathic practice are designed to help individuals increase their health span while taking into consideration the extent of disease, a variety of modalities or tools of applicability, and patient choice and values; however, exercise prescriptions stand out as part of a foundational approach nearly ubiquitous and necessary for almost everyone. This is for good reason, since the health benefits of exercise are numerous and naturopathic doctors tend to have a solid background in this field. One common use of exercise prescriptions is for the improvement of cardiorespiratory fitness (CRF). In keeping with a well-accepted mandate of being evidence-informed, CRF prescriptions should have precedent in the scientific literature. It is the clinician’s role to further individualize the recommendation to ensure success. The purpose of this entry is to highlight usable, evidence-based protocols for improving CRF.

As proud advocates of “prevention is the best medicine,” naturopathic doctors are experts in lifestyle plans and optimization. One well-studied marker of health is V̇O₂ max, or maximal oxygen uptake during exercise, measured as millilitres per kilogram per minute (ml/kg/min). V̇O₂ max is the best-established marker of cardiorespiratory fitness (CRF). Below is a list of evidence-based exercise prescriptions that can improve CRF, contributing to potential enhancements in both health span and life span. Whether working with well-seasoned athletes or those suffering from chronic disease, naturopathic doctors have the tools to apply the science of exercise physiology in a safe and effective manner for the purpose of improving CRF.

Building an Exercise Program Focused on Improving CRF

To quantify results of an exercise program, it can be valuable to have objective baseline measurements. Metabolic analysis through an active metabolism ramp test can provide accurate results for V̇O₂ max as outlined here. The author’s experience is that using these assessments in clinical practice improves compliance, inspires an improved naturopathic doctor-patient relationship, and adds extra value to the program because breathing, vascular, and mitochondrial limitations can be identified—and therefore enhanced—through these assessments. A baseline result will often include a reflection on the range of normal values for V̇O₂ max for the individual’s age and gender. If metabolic analysis technology for basic fitness assessments is not available, subjective reporting by way of the rate of perceived exertion (RPE) scale for a specific type of exercise or through a standardized in-office test can be used instead.

The value of CRF enhancement is not limited to but may include the reduction in all-cause mortality associated with increases in V̇O₂ max; blood-pressure improvements; as well as glucose, mood, quality-of-life, sleep, energy, and cholesterol control. A typical follow-up schedule to reassess CRF is at 12 weeks. For those with a pulmonary, cardiac, or skeletal muscle condition, follow-up may be set at a later date to account for the minimal amount of exercise that can be completed per week. The most common goal to enhance CRF is to achieve a V̇O₂ max increase of 4 ml/kg/min after 12 weeks, and to continue with this increment going forward. Because V̇O₂ max is focused on heart rate, more effort will be required to increase the heart rate to its target as CRF is enhanced, thereby reducing physiological tolerance or adaptation.

Many studies have been done assessing exercise protocols for the purpose of enhancing CRF. They commonly attempt to discern differences in effectiveness between types of exercise, intensity, frequency, and duration. One meta-analysis showed that many different types, durations, frequencies, and intensities of exercise have demonstrated efficacy in improving CRF. In a young, healthy population, high-intensity submaximal and near-maximal training (≈ 80–92.5% V̇O₂ max) produces equivalent gains in V̇O₂ max. In addition, they discovered that training at a heart rate of > 60% V̇O₂ maxis likely to improve oxygen uptake in healthy adults. An important finding from this research was that, with high-intensity and/or sprint training, exercising less frequently is actually ideal. For medium- and low-intensity training, exercising more times per week is best. Workout lengths range from 2 min of active work to 60 min of active work in the low-intensity groups. Frequency of training is up to three days per week. Duration of the entire protocol usually ranges from 6 to 12 weeks.

Types of Exercise Training

Luckily, there exists a range of intensities and types of exercise to choose from. Ideally, the goal on a V̇O₂ max enhancement plan is to work up to high-intensity interval-training protocol since it provides a slight advantage for improving CRF. In a healthy person with no health conditions, an evidence-informed, high-intensity interval training would look like this:

Risks associated with this type of protocol are many, and it is commonly used for the experienced exerciser or for in-office protocols such as naturopathic doctor or personal trainer–guided HIIT. To accomplish this protocol, it is helpful to use a heart-rate monitor in order to achieve the desired level of exertion during the active phase. If one is not available a rate of perceived exertion (RPE) scale can be used. The active phase of this protocol uses an RPE of 9–10, which refers to the intensity at which the patient is at peak effort and cannot talk.

For a session like this, it is important to review and implement a warm-up routine as well as recovery nutritional and physical support. Relative contraindications include physical limitations and pathologies of the joint, heart, and lung; subjective limitations include mobility, pain, energy, etc. A recommended periodization of training will tend to work up to this gold-standard protocol.

Improving V̇O₂ max can be accomplished at any age. This means setting goals for weekly frequency, intensity, and duration of activity to create a physiologic change. Evidence-informed protocols for medium continuous training look like this:

This type of protocol is helpful for the low-experience exerciser. It is also usable for anyone with physical conditions impacting their ability to achieve a high heart rate, including muscle and tendon chronic injury and cardiovascular disease. Those with chronic fatigue or mitochondrial dysfunction may also fit into this initial or low-intensity stage of training. An easier way of achieving this protocol would be to set a goal of 10,000 steps per day, which, as a goal, has been shown to raise V̇O₂ max for a population over a 12‑week duration.

For those short on time and who maintain a relatively high level of health otherwise, sprint training is well indicated and effective. This is also great for the high-level athlete and high-experience exercisers.

Sprint training is almost as effective as HIIT and can be better tolerated for certain individuals.

CRF enhancement is likely more efficient if limitations are addressed. These include the lungs’ ability to take in oxygen and expel CO₂, the heart’s ability to pump oxygenated blood to the tissues, efficiency of capillary’s efficiency to distribute oxygen to cells, as well as muscle mitochondrial density and activity. All these factors basically translate to how much oxygen utilization is possible in a particular tissue. Building mitochondrial density can be of significant value for this process, and it is achieved through increases in muscle mass. For those unable to complete highly metabolic aerobic training as described above, a preparation period of strength training can be valuable.

A common protocol to support general strength improvement for the purpose of building muscle mass may look as follows:

• 2–3 times per week for 8–12 weeks
• Three sets of 8–12 reps
• RPE of 8–10

Using the following exercises:

• Bench press or inclined bench press
• Shoulder press
• Bent-over row
• Squat
• Deadlift

The key here is that exercise prescriptions need to be individualized and a commitment to a 12–24‑week exercise plan is often required to observe objective change in CRF.

A range of studies have been completed on V̇O₂ max enhancement using cycling, walking, running, rowing, swimming, and a variety of high-intensity interval-training and continuous medium intensity–training splits, that can accommodate individual preference. Choosing the right version and observing the predicted results can be highly motivating and satisfying. Finding a health-care practitioner with a team/coach-based approach with consistent check-ins improves compliance and will improve the goal of four points of V̇O₂ max enhancement every 12 weeks.