Analgesic Medication Use During Exercise-Based Rehabilitation in Individuals With Low Back Pain: A Call to Action

Chronic low back pain (LBP) is one of the most common, and sometimes most challenging, conditions to treat in an orthopedic setting. Though exercise-based rehabilitation is the standard of care for this patient population, only 20% of patients currently participate in this type of physical therapy in isolation.¹ Furthermore, in most cases, LBP management includes pharmacologically based pain management in the form of analgesic medications. This use of analgesics is potentially challenging, because physical therapists are faced with the paradox that, although exercise under the influence of analgesic medications can impair muscle adaptation in healthy individuals,^2,3 in individuals with pain, analgesics are often used to circumvent symptoms that limit exercise tolerance (Figure). A representative example of this impaired adaptation is that in individuals with LBP the stabilizing muscles of the trunk do not consistently hypertrophy in response to exercise, despite short-term improvements in strength.⁴ Indeed, the lack of paraspinal muscle hypertrophy is thought to contribute to the high rates of recurrence in this population.^4,5 Given the high proportion of patients with LBP who use analgesics with therapeutic exercise, and the opposing effects of their use on muscle adaptation, motor drive, and exercise tolerance, it is possible, and perhaps likely, that analgesic use is a fundamental detractor to the outcome of exercise-based rehabilitation. Remarkably, however, there are essentially no objective data in the field on how patients with LBP use analgesic medications relative to exercise-based rehabilitation. As such, the field is currently in a situation where a lack of definitive data could be impeding optimal rehabilitative exercise, treatment, and functional adaptation.

Figure.

A conceptual framework for the balance between the potentially negative influence of analgesic medications on muscle growth and activation, and the positive influence of analgesic medications on exercise tolerance. The influence of these factors in tipping the scale toward functional improvement is also founded on the underlying health of the targeted muscles.

Clinical practices for analgesic management of individuals with LBP vary widely based on geography, diagnostic testing, and patient presentation. Even as practitioners continue with an ongoing battle to reduce an opioid use rate of more than 75% in patients with long-term (>2 year pain duration) LBP, opioids remain the most frequently prescribed analgesic medication in this population.^6,7 Opioids, along with nonsteroidal anti-inflammatory drugs (NSAIDs), account for over 50% of analgesic drug use in this population. This is significant, because NSAID use in pain-free individuals with healthy muscle reduces regenerative capacities,^2,3 mitochondrial function,⁸ and protein synthesis⁹ of the exercised skeletal muscle in response to exercise, leading to reduced muscle growth and performance adaptations.^10,11 Moreover, ibuprofen, one of the most commonly utilized NSAIDs in musculoskeletal conditions, reduced exercise-induced muscle growth by 50% in an animal model.¹²

Several mechanisms have been proposed to explain impairments in the adaptive response to exercise after NSAID and opioid use. In NSAIDs, there is a reduction in satellite cell differentiation,³ a process that is essential for muscle regeneration. There is also inhibition of cyclooxygenase activity, which is thought to be necessary for muscle growth, and, lastly, attenuation of mitochondrial function,⁸ which reduces endurance capacity of muscle. In human studies, the influence of NSAIDs is less clear. In healthy older adults, NSAIDs protected against inflammation-induced muscle weakness and age-related muscle loss,¹³ despite no improvement in muscle size.¹⁴ Opioids are known to decrease corticospinal excitability^15,16 and increase exercise-induced central fatigue through intracortical inhibition,¹⁷ which could have a substantial effect on motor drive and muscle activation during exercise. Remarkably, however, the specific impact of opioids, muscle relaxants, and central nervous system inhibitors on muscle physiology is largely unknown.^18,19

In addition to medication type, the impact of medication timing in the periexercise period is a potentially important factor influencing musculoskeletal adaptation in response to exercise. Anecdotally, clinicians typically recommend that patients take their analgesic medications immediately prior to exercising so that they are able to tolerate more activity related to their rehabilitation.²⁰ This is likely based on the idea that pre-exercise use of analgesic medication improves the ability of a pain-limited patient to tolerate an exercise stimulus that is sufficiently “stressful” to induce an adaptative response. However, the pre-exercise analgesic use recommendation does not take into account the fact that this impedes the aforementioned processes necessary for muscle adaptation to exercise.^21,22 In contrast, post-exercise use does not influence muscle inflammatory markers, prevent exercise-induced muscle soreness, or reduce muscle hypertrophy potential, although protein synthesis is still somewhat reduced.^23,24 Regardless, the field is currently limited to anecdotally driven evidence and lacks systematically collected robust data in this patient population.

Without doubt, it should be clear to health care providers interfacing with patients with LBP that the type and timing of analgesic medications can impact the adaptive response to therapeutic exercise, and therefore, clinical outcomes. As such, in this “call to action,” we contend that the field needs to prioritize systematic documentation of analgesic use and its influence on exercise outcomes. These actions will provide foundational data that will allow physical therapists to generate clinical guidelines and recommendations relative to: (1) the influence of different classes of analgesics on exercise performance and tissue adaptation, and (2) optimal timing of analgesic use relative to the patient's rehabilitation. Through their presence at the front line of rehabilitative care, physical therapists are uniquely positioned to spearhead these documentation efforts and work in concert with medical professionals to implement recommendations based on these data. Given this position, when supporting data become available, it may be time to consider broadening the scope of practice of physical therapists to include providing education and/or recommendations on the impact of type and timing of analgesic medications on physical therapy outcomes. Ultimately, the implications of these actions for human health are a more complete understanding of treatment interactions for commonly prescribed conservative management modalities and evidence for novel patient-specific, cost-effective approaches, resulting in improved function and health over the lifespan.

Author Contributions

Concept/idea/research design: B. Shahidi

Writing: B. Shahidi, S. Schenk, K. Raiszadeh

Data collection: B. Shahidi

Project management: B. Shahidi

Fund procurement: B. Shahidi

Consultation (including review of manuscript before submitting): K. Raiszadeh

Funding

This work was supported by the Foundation for the National Institutes of Health (no. R01HD100446). The funder played no role in the writing of this manuscript.

Disclosure

The authors completed the ICMJE Form for Disclosure of Potential Conflicts of Interest and reported no conflicts of interest.