The Dose Makes the Difference

Of the thousands of modern medications available, there are very few that can hold a candle to the power of exercise. This fact is true on account of the accessibility, cost, effectiveness and overall simplicity that movement provides us. To claim ‘exercise is the best medicine’ is no hyperbole, but it still can seem impossible for many of our patients. As new practitioners, it can be hard to know where to start our patients to effectively meet them at their current state while also meeting the threshold for evidence-based practice. Through this article, we will journey to understand the science behind exercise dosing and break down best practices for the clinic.

Current State of Exercise Prescription

In our schooling, we learn the ins and outs of all of the ‘-ologies’ that dictate how exercise impacts the different functions of muscle contraction. Unfortunately, this information seems to be lost in the real world of clinical practice, where sets and reps are haphazardly assigned. If there were ever to be an ‘off the shelf’ bottle of exercise, it would likely contain 3 sets of 8-12 repetitions². The American College of Sports Medicine recommends this range for novice exercisers, which includes most of our patients, but it doesn’t really consider why they’re coming to see us in the first place (primary conditions and their respective comorbidities make patients much more complicated). For this reason, they need exercise that’s tailored to their specific conditions and needs.

Why Dosing Matters

Just as physicians require precise parameters to accurately prescribe medication, we must apply the same rigor when dosing exercise. To understand the importance of this precision, we should consider both scientific and philosophical perspectives. Scientifically, leveraging the body's physiology to enhance function necessitates tailoring exercises to focus on specific aspects such as muscle endurance, power, aerobic capacity, or neuromuscular control. These individualized approaches often extend beyond generic, standardized guidelines. Philosophically, our patients trust us to provide care that is personalized and effective, with clear explanations for our choices. We should always be able to justify each exercise we prescribe with valid reasoning. Without grounding our decisions in evidence, we cannot confidently assert that we are practicing at the highest level of our well-earned licensure.

Approaches to Dosing

Our profession is quite diverse in its scope and as a result we have multiple methods of dosing exercise. The following are some of the most prominent approaches that are used with typical patient populations:

• Ortho:

  • One of the most fundamental aspects of exercise is undoubtedly sets and repetitions. All too easy to arbitrarily assign, these numbers (especially repetitions) really need to be assigned with a purpose in mind. As seen below, all forms of sets and repetitions have some impact on functions of strength, power hypertrophy and muscular endurance. This is where our clinical reasoning continues to find its importance to associate repetitions with the deficits of the client. For example, with a patient with quadricep weakness would benefit from repetitions based on muscular endurance to improve gait as it is typically a continuous activity. 

• Neuro:

  • In all of us lies a complex system of electrical signals that drives everything from our higher thinking down to the ability to move our toes. Those that fall victim to disorders in the neurological system need more than a defined number of sets and reps to determine their recovery. Integration of neuroplasticity principles is essential for recovery in these scenarios. For us, this means we need to be familiar with the 10 rules that contribute towards neuroplasticity³ .

    • Use it or lose it: Skills need to be used consistently or performance will degrade

    • Use it and improve it: Training and challenging of a function will improve that function

    • Specificity: Plastic changes will only occur for functions similar to that which is being trained

    • Repetitions matter: Skills need to be performed multiple times 

    • Intensity: Training for 20+ minutes at moderate to high intensity optimizes neuroplastic changes

    • Time: Training earlier in the recovery timeline is more effective

    • Saliency: Training should be made relevant to the patient’s essential functions

    • Age matters: Plasticity occurs more readily in younger brains

    • Transference: Training a function can improve the acquisition of similar behaviors

    • Interference: Training a function can interfere with the acquisition of other behaviors

  • Systemic:

    • Unfortunately, chronic conditions continue to dominate in the leading causes of death in the United States. Among these, cardiovascular and pulmonary complications are inevitable and will be present in our profession. Consequently, these conditions strongly impact the way that we are able to dose our interventions. The RPE (left) and dyspnea (right) scales are proven methods to monitor patient response to exercise and need to be considered alongside systemic pulmonary and cardiovascular conditions. As a general rule for cardiovascular rehabilitation, working in the 11-13 range of the RPE scale for focusing on duration is recommended whereas working in the 13-15 range for short intervals is recommended for pulmonary rehabilitation. To track aerobic capacity over time, the dyspnea scale is invaluable as a simple objective measure that can be used in both of these populations¹ .

Clinical Application

During your time in the clinic you are likely to encounter a wide variety of cases ranging from simple tendinopathies to more complex conditions with acute and chronic aspects  spanning multiple systems. Even though we have designated dosing approaches for different systems, treating the patient as a whole requires that we use all of them at once. Up or down-weighting each based on what we see is just part of the game that we play with our clinical reasoning. Ultimately, the common goal of any exercise that we are guiding our patients through is function. Prioritizing interventions that align with what truly matters in our patient’s life or that lay the groundwork for more meaningful training in the future should always guide our approach. What matters most is our patient’s successful return to their daily life and roles.

Parting Words

At its core, exercise is far more than movement. Exercise is medicine, tailored not only by science but by the hands of those who apply it with intention. As new practitioners, the challenge lies not in simply prescribing motion, but in crafting interventions that are driven by evidence, refined by reasoning, and infused with meaning. Our success is not measured by the elegance of our treatment plans or the complexity of our rationale, but by our patient’s ability to return to the life they value. In a field full of nuance, we are not just meeting the standard of care. We are raising it. After all, in our hands, exercise isn’t generic. It’s personalized, potent, and powerful.

References:

1. Jaime Paz, West M, Panasci K, Greenwood K. Acute Care Handbook for Physical Therapists. 5th ed. Elsevier; 2019.

2. Krzysztofik M, Wilk M, Wojdała G, Gołaś A. Maximizing Muscle Hypertrophy: A Systematic Review of Advanced Resistance Training Techniques and Methods. Int J Environ Res Public Health. 2019;16(24):4897. doi:10.3390/ijerph16244897

3. Fell D, Lunnen K, Rauk R. Lifespan Neurorehabilitation. F.A. Davis Company; 2018.

Disclaimer:

We are current Doctor of Physical Therapy (DPT) students sharing information based on my formal education and independent studies. The content presented in this newsletter is intended for informational and educational purposes only and should not be considered professional medical advice. While we strive to provide accurate and up-to-date information, our knowledge is based on our current academic and clinical rotations and ongoing learning, not extensive clinical practice.