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Contributions of Treatment Theory and Enablement Theory to Rehabilitation Research and Practice

      Abstract

      Scientific theory is crucial to the advancement of clinical research. The breadth of rehabilitation treatment requires that many different theoretical perspectives be incorporated into the design and testing of treatment interventions. In this article, the 2 broad classes of theory relevant to rehabilitation research and practice are defined, and their distinct but complementary contributions to research and clinical practice are explored. These theory classes are referred to as treatment theories (theories about how to effect change in clinical targets) and enablement theories (theories about how changes in a proximal clinical target will influence distal clinical aims). Treatment theories provide the tools for inducing clinical change but do not specify how far reaching the ultimate impact of the change will be. Enablement theories model the impact of changes on other areas of function but provide no insight as to how treatment can create functional change. Treatment theories are more critical in the early stages of treatment development, whereas enablement theories become increasingly relevant in specifying the clinical significance and practical effectiveness of more mature treatments. Understanding the differences in the questions these theory classes address and how to combine their insights is crucial for effective research development and clinical practice.

      Keywords

      List of abbreviations:

      ICF (International Classification of Functioning, Disability and Health)
      Rehabilitation treatments target clinical phenomena ranging from body structure to participation (to use terminology from the International Classification of Functioning, Disability and Health [ICF]),

      World Health Organization. International Classification of Functioning, Disability and Health (ICF). Available at: http://www.who.int/classification/icf. Accessed November 30, 2012.

      use techniques that vary from assistive devices to psychoeducational programs, and are provided to individuals of all ages with minor to major short- to long-term disabilities. Is it any wonder that no unified body of theory has evolved to support the field? Two broad classes of theory are relevant to rehabilitation, referred to here as *treatment theory
      • Keith R.A.
      The role of treatment theory.
      • Lipsey M.W.
      Theory as method: small theories of treatment.
      and *enablement theory.
      • Whyte J.
      Directions in brain injury research: from concept to clinical implementation.
      • Whyte J.
      • Barrett A.M.
      Advancing the evidence base of rehabilitation treatments: a developmental approach.
      (Words and phrases that are specifically defined in supplemental appendix S1 [page A9 of this supplement and online at http://www.archives-pmr.org/] are marked with an asterisk and italicized when initially used.) These 2 theory domains make important but distinct contributions to rehabilitation research and practice. Moreover, the distinction between the theory domains has implications for how researchers and clinicians are trained, how research is funded, and how treatment development can be enhanced, which is explored in this article.

      Treatment Theory

      Treatment theory refers to a class of specific theories that specify mechanisms by which the *active ingredients of a treatment produce change in the *treatment target, the aspect of function that is directly impacted by the treatment.
      • Keith R.A.
      The role of treatment theory.
      • Lipsey M.W.
      Theory as method: small theories of treatment.
      • Whyte J.
      Directions in brain injury research: from concept to clinical implementation.
      • Whyte J.
      • Barrett A.M.
      Advancing the evidence base of rehabilitation treatments: a developmental approach.
      In doing so, they distinguish the active ingredients (ie, those that are involved in producing the clinical change) from *inactive ingredients, something that is fundamental to defining, evaluating, and disseminating an effective treatment.
      • Whyte J.
      A grand unified theory of rehabilitation (we wish!). The 57th John Stanley Coulter Memorial Lecture.
      • Whyte J.
      • Gordon W.
      • Rothi L.J.
      A phased developmental approach to neurorehabilitation research: the science of knowledge building.
      • Dijkers M.P.
      • Hart T.
      • Tsaousides T.
      • Whyte J.
      • Zanca J.M.
      Treatment taxonomy for rehabilitation: past, present and prospects.
      A treatment's active ingredients can be further divided into *essential ingredients and other active ingredients. Essential ingredients are those that can be used to distinguish among or define categories or classes of treatment. Other active ingredients may be combined with the essential ingredients to moderate their impact, but these ingredients do not define the treatment category. For example, goal setting interventions have been shown to affect varied aspects of human performance
      • Locke E.A.
      • Latham G.P.
      Building a practically useful theory of goal setting and task motivation.
      ; however, they are not essential ingredients in most treatments (ie, some improvement will take place with or without goal setting). Adding goal setting to the ingredients a therapist uses may enhance the impact of many different treatments that aim to change complex human behaviors.
      How do we precisely decide the treatment target? For example, in the case of progressive resistance exercises, should the target be framed as muscle strength, muscle bulk, protein synthesis, or something else again, given that all of these changes are likely to occur in parallel? It is proposed that the treatment target be defined as the most proximal clinical characteristic for which the change has functional significance—muscle strength in this example. That is, if muscle hypertrophy without improved strength was observed, this would not be regarded as a successful rehabilitation treatment (though it might be a successful bodybuilding treatment). On the other hand, if an increase in strength without hypertrophy or protein synthesis was observed, this might be surprising, but it would still be regarded as a successful treatment outcome.
      A wide range of treatment targets receives attention in rehabilitation, and they occupy different conceptual levels that are consistent with the ICF and similar conceptualizations.

      World Health Organization. International Classification of Functioning, Disability and Health (ICF). Available at: http://www.who.int/classification/icf. Accessed November 30, 2012.

      • Keith R.A.
      The role of treatment theory.
      • Whyte J.
      Assessing medical rehabilitation practices: distinctive methodologic challenges.
      Examples of treatments and treatment targets at the ICF levels are shown in table 1.
      Table 1Levels of treatment
      Treatment LevelTreatment TargetTreatment Intervention
      Body structureLength of tendonSerial casting
      Body functionMuscle strengthProgressive resistance exercise
      ActivityHousehold mobilityAluminum walker
      ParticipationEmployer attitudes toward disabled employeesEmployer education and sensitivity training
      The treatment theories that underlie these different interventions are similarly diverse, focusing on perspectives as distinct as tissue remodeling (eg, MacKay-Lyons
      • MacKay-Lyons M.
      Low-load, prolonged stretch in treatment of elbow flexion contractures secondary to head trauma: a case report.
      ) and social psychological adaptations,
      • Hart T.
      • Evans J.
      Self-regulation and goal theories in brain injury rehabilitation.
      and defining active ingredients that include physical forces, cognitive stimuli, and learning experiences. Examples of treatment theories and hypothetical essential active ingredients are shown in table 2.
      Table 2Treatment theory examples
      TreatmentTargetEssential Ingredients
      Progressive resistance exercisesIncrease in muscle strength (torque)Repetitive muscle contraction against increasing resistance
      Neutral cues for goal neglect
      • Sullivan K.J.
      • Cen S.Y.
      Model of disablement and recovery: knowledge translation in rehabilitation research and practice.
      Completing goal-directed activitiesRandomly delivered alerting tone with previously trained significance
      Serial casting for joint contractureLength of soft tissuesProlonged tension
      Hemi-dressing trainingIndependent dressing in reasonable timeRepeated performance with error feedback about physical strategies

      Enablement Theory

      In rehabilitation the ultimate clinically important aim is often remote from the treatment target as defined here. Generally when the treatment target is a body structure or a body function deficit (ie, an impairment), the ultimate clinical aim is some activity or aspect of participation that is limited by that impairment. Similarly, a *patient may receive treatment to enhance a specific activity (eg, driving) in the belief that it is an activity limitation that is a crucial obstacle to aspects of participation. Treatment theories, however, have nothing to say about the ultimate clinical impact of such treatments. That impact depends on a wealth of other abilities and limitations that coexist in the patient, and on aspects of their physical and social environment. The treatment's *mechanism of action likely has no impact on these other deficits. For example, treating an isolated plantar flexion contracture may enhance ambulation, but treating the same contracture in a patient with significant dynamic balance deficits may not.
      In contrast, enablement theory hypothesizes the nature and strength of the relations among clinical characteristics (eg, how important is quadriceps strength to ambulation ability?) and predicts where changes will occur in response to perturbations or interventions elsewhere (eg, how much improvement in ambulation function would be predicted for a 10% increase in quadriceps strength in a patient with coexisting mild balance impairment?).
      • Whyte J.
      • Barrett A.M.
      Advancing the evidence base of rehabilitation treatments: a developmental approach.
      Enablement theory, however, has nothing to say about how to change any of the variables in the model. Indeed, enablement theory predicts the same improvement in ambulation for a 10% strength change, regardless of how that strength change is achieved (exercise, injection of trophic factors, etc). Thus, the tools for change must be supplied by treatment theories, but the breadth and nature of the resultant distal clinical impact is predicted by enablement theories.
      Figure 1 provides a simplified example of an enablement theory in which the various body structures that might influence joint range of motion are identified and their (hypothetical) causal weights relative to one another are specified. The relations have been oversimplified to indicate that body function variables affect activities and so forth. In reality, however, similar enablement links can be found within an ICF level when a complex activity (eg, dressing) relies on the combined execution of a number of smaller activities (eg, pinching, reaching). It is unrealistic to build an enablement model of all human function because this would require specifying an enormous number of variables and the complex interactions among them. However, local enablement models can be built that identify the most important variables affecting specific functional domains, such as ambulation and language expression. For example, Sullivan and Cen
      • Sullivan K.J.
      • Cen S.Y.
      Model of disablement and recovery: knowledge translation in rehabilitation research and practice.
      proposed such a model, relating key impairments to aspects of walking performance using structural equation modeling.
      Figure thumbnail gr1
      Fig 1A hypothetical and simplified enablement model. The existence of clinical characteristics at all levels of the ICF is noted with arrows, indicating causal influences between them. Each clinical characteristic tends to be influenced to varying degrees by multiple different characteristics from the level below. Several hypothetical body structure characteristics are shown as relevant to determining a specific body function, passive elbow extension. The causal weight of each arrow is indicated with a hypothetical value ranging from 0 (no impact on the next characteristic) to 1 (exclusively determining the value of the next characteristic).
      Considering these 2 forms of theory reveals their contrasting and reciprocal roles. Treatment theories give us tools for changing specific functional variables, the treatment targets. Enablement theories help us understand the remote, but clinically important, effects of the treatments we undertake.
      • Whyte J.
      • Barrett A.M.
      Advancing the evidence base of rehabilitation treatments: a developmental approach.
      Assuming we want our treatments to be effective (ie, to change what they are intended to change) and have clinically useful functional impact, we must combine these forms of theory into a unified vision. This has to be done by researchers and, even more so, by clinicians, as will be subsequently argued.

       Contributions of treatment theory and enablement theory to rehabilitation research

      Both treatment theory and enablement theory make important but quite distinct contributions to rehabilitation research. Treatment theory is key to meaningfully defining rehabilitation treatments and to developing the structure of a useful *taxonomy by which to organize them.
      • Dijkers M.P.
      • Hart T.
      • Tsaousides T.
      • Whyte J.
      • Zanca J.M.
      Treatment taxonomy for rehabilitation: past, present and prospects.
      When we name treatments, communicate about them, study them, or train others to deliver them, it is important that we define them in terms related to the reasons for their clinical effectiveness: if we began referring to progressive resistance exercises as activities performed on Mondays, Wednesdays, and Fridays, this category would cease to convey the active ingredients of the treatment. A treatment taxonomy built on treatment theories provides a useful guide to treatment research because whole branches of the taxonomy can be pruned or encouraged to sprout, in response to results of clinical studies. In the absence of a treatment theory that specifies what target can be changed using what ingredient(s) impacting through what mechanism of action, clinical studies can only eliminate or support 1 specific treatment, but they do not help to build a science of treatment effectiveness.
      • Whyte J.
      Assessing medical rehabilitation practices: distinctive methodologic challenges.
      • Whyte J.
      Mechanisms of recovery of function following CNS damage.
      A treatment that is effective without the researcher understanding why will not lead to hypotheses about the kinds of patients for whom it will be most effective, or how we could modify the treatment to make it even more effective.
      Treatment theory is also critical to the rigorous design of clinical research, particularly in early phases of treatment development (ie, proof of concept, early efficacy trials).
      • Whyte J.
      Directions in brain injury research: from concept to clinical implementation.
      • Whyte J.
      • Barrett A.M.
      Advancing the evidence base of rehabilitation treatments: a developmental approach.
      • Hart T.
      Treatment definition in complex rehabilitation interventions.
      • Whyte J.
      Using treatment theory to refine the designs of brain injury rehabilitation treatment effectiveness studies.
      Treatment theory guides selection of inclusion and exclusion criteria. Postulating a mechanism of action helps to identify what kinds of patients would be expected to respond to the treatment. Treatment theory also facilitates the selection of appropriate outcome measures because the most critical initial outcome is a measured change in the treatment target.
      • Whyte J.
      • Barrett A.M.
      Advancing the evidence base of rehabilitation treatments: a developmental approach.
      • Whyte J.
      Using treatment theory to refine the designs of brain injury rehabilitation treatment effectiveness studies.
      Because treatment theory specifies the treatment's active ingredients, it offers a basis for creation of an assessment of treatment adherence, that is, to what degree did the study subjects receive those active ingredients and the comparison group subjects did not.
      • Whyte J.
      Mechanisms of recovery of function following CNS damage.
      It also allows replication of the research and effective dissemination of a proven treatment by clearly defining the ingredients that must be replicated or disseminated.
      • Dijkers M.P.
      • Hart T.
      • Tsaousides T.
      • Whyte J.
      • Zanca J.M.
      Treatment taxonomy for rehabilitation: past, present and prospects.
      Despite their differences, treatment theory also contributes importantly to the development of enablement theory. Treatment results provide important evidence about hypothesized causal links among ICF characteristics. For example, in later stages of clinical research, one may specify a primary outcome (treatment target) and ≥1 secondary outcomes that are expected to change based on relevant enablement theories. If treatment-induced change in the target is confirmed, one can assess whether the predicted distal changes occur and, accordingly, support or refute the enablement theory that predicted this distal change. For example, one might hypothesize that spasticity is an important obstacle to active upper extremity reaching and grasping (via enablement links) and predict that effective treatment of upper extremity spasticity would enhance reaching and grasping. If successful control of spasticity does not result in improved reaching and grasping, however, this may suggest alternative enablement models that postulate stronger links between muscle recruitment and reaching and grasping, and weaker links between spasticity and these activities.
      • Whyte J.
      • Robinson K.
      Pharmacological management of spasticity.
      Enablement theory is also indispensable to progress in rehabilitation research, particularly in the later phases of treatment development.
      • Whyte J.
      • Gordon W.
      • Rothi L.J.
      A phased developmental approach to neurorehabilitation research: the science of knowledge building.
      For the many treatments where the desired clinical aim is remote from the treatment target, clinical utility of treating the more proximal target depends on the strength of those distal enablement links. For example, lower extremity strengthening is likely to be most effective in reducing the risk of falls in patients with intact balance and vision, assuming that these characteristics also have substantial impact on the risk of falling. Lower extremity strengthening exercises may effectively strengthen most patients, but the impact on falls may be restricted to patients without these other impairments. An enablement model of fall risk will suggest either that effectiveness trials of strengthening treatments to prevent falls should be restricted to samples without balance and vision problems, or that additional treatments for balance and visual deficits need to be combined with the strengthening treatment to impact fall risk in a broader sample of patients.
      • Tinetti M.E.
      Preventing falls in elderly persons.
      Enablement theory may also help predict the generalization of treatment benefits. For example, would lower extremity strengthening that enhances safe ambulation generalize to stair climbing? This depends on the role of lower extremity strength in these 2 different activities. It is quite possible that greater improvement in lower extremity strength would be needed to impact stair climbing than to improve ambulation, such that one might not predict generalization of benefits from the same level of increased strength to activities that have different strength requirements.

       Contributions of treatment theory and enablement theory to clinical practice

      Both treatment theory and enablement theory are as critical to rehabilitation treatment planning and implementation as they are to research. Just as treatment theory helps to select inclusion and exclusion criteria for clinical studies, it helps to identify whether a treatment's known or hypothesized mechanism of action is relevant to a particular patient's clinical profile. For example, if progressive resistance exercises require repetitive muscle contraction against increasing resistance, then selecting this treatment for a patient who cannot or will not voluntarily contract their muscles is inappropriate.
      Once selected, a treatment may need to be individualized or tailored to the specific features of an individual patient. Treatment theory specifies what tweaks in the treatment can be made without undermining its mechanism of action. Thus, an understanding of the relevant treatment theory helps a clinician match the treatment to patients who are likely to respond to it. If the treatment is not even effective in altering its treatment target, it is hardly worth looking for a broader clinical impact. As previously noted, however, bringing about a change in the treatment target alone is not sufficient to guarantee a clinically beneficial treatment result. In principle, treatments can be directed toward targets at any level of the ICF, as shown in figure 2. When the treatment target is at the same ICF level as the outcome of clinical importance (cells along the diagonal), there is no need to invoke enablement theory to predict the ultimate clinical impact; the treatment target is clinically important in its own right. However, when the outcome of clinical interest is distal to the treatment target (ie, cells in the upper right), enablement theory is required to predict the extent of clinically significant impact of the treatment. This is also true, in an even more indirect sense, for cells in the lower left. In these instances, an intervention at a more macro functional level (eg, installation of a ramp to the individual's front door that facilitates mobility in the community) might influence a more micro level (eg, body structure in the form of skin integrity), either negatively (eg, by leading to longer intervals of wheelchair sitting during travel causing skin breakdown) or positively (eg, by enhancing mood and, therefore, motivation to maintain good skin care).
      Figure thumbnail gr2
      Fig 2An illustration showing that both treatment and outcome measurement can take place at any ICF level. Treatment levels are indicated by rows and outcome levels by columns. When the outcome is measured at the same level as the intervention (light colored cells along the diagonal), there is little need to invoke enablement theory. For dark shaded cells above and below the diagonal, however, the treatment may or may not induce substantial change in distal clinical outcomes, as specified by the predictions of enablement theory.
      Enablement theory asks the following question: among those patients who experience treatment-induced change in the treatment target, what impact is expected on distal clinical outcomes A, B, and C? As previously noted, the same degree of exercise-induced strengthening in the leg extensors might lead to improved ambulation in a patient with few other impairments, and no change in ambulation in a patient with coexisting balance and visual deficits. This latter person's ambulation problem cannot be solved with better strengthening exercises. Rather, one must conceptualize what other factors are also limiting clinically important function in addition to the treated impairment. If these other factors additionally substantially limit function, this should lead to the conclusion that the patient will not ultimately benefit from the treatment (even though it leads to stronger muscles); therefore, it is pointless to undertake it. Alternatively, if effective treatments are available for the additional limiting impairments, then a combination of treatments (delivered simultaneously or successively) may provide meaningful clinical benefit.

       Implications for the field

      The distinction between treatment theory and enablement theory has important implications for the process of fostering clinical research and training.
      • Whyte J.
      Directions in brain injury research: from concept to clinical implementation.
      • Whyte J.
      • Barrett A.M.
      Advancing the evidence base of rehabilitation treatments: a developmental approach.
      This distinction is relevant to the developmental process of clinical research, the funding and training of clinical researchers, and the training of future clinicians.

      Clinical Research as a Developmental Process

      The rationale for a new treatment may make use of both treatment theory and enablement theory; that is, one may recognize that most patients' function is limited by several interacting factors but may concentrate on the development of a new or improved treatment for only 1 of these factors. Once armed with this rationale, however, early phases of treatment development typically rely most heavily on treatment theory because this is the domain that will guide optimization of treatment strength and demonstration of efficacy in changing the treatment target. For this reason, these early stages of research are likely in the hands of investigative teams with rich knowledge of the mechanism of action of the treatment and the body structure, function, or activity the treatment is designed to change. Once efficacy at the level of the treatment target is determined, enablement theory looms larger in guiding research on the ultimate clinical utility of the treatment; that is, the question shifts from “does the treatment have the hypothesized effects on the target?” to “in what kinds of patients does use of this treatment have important functional benefits?” Consider again the example of progressive resistance exercises. The investigators most likely to innovate in the area of exercise treatment are those with sophisticated knowledge of muscle physiology and metabolism, and of the differential effects of different forms of muscular challenge. However, there is little reason to think these same investigators would be knowledgeable about the role of balance and proprioception in gait, or about how the strength demands of gait vary with the terrain patients have to negotiate. In contrast, investigators with a sophisticated understanding of gait and its functional requirements (ie, enablement modeling of gait) have the expertise to predict the functional impact of exercises that produce a specific increase in strength across a heterogeneous group of patients. Therefore, full maturation of rehabilitation treatments is likely to require a handoff from those investigators more focused on treatment theory to those more focused on enablement theory.

      Training of Researchers

      The movement from treatment theory- to enablement theory-guided studies is also relevant to the training of future researchers. Do we want to train individual researchers in the full developmental sequence? Is it realistic for any 1 investigator or even group of investigators to have a sophisticated understanding of a specific treatment theory domain and the enablement model that would help predict all distal treatment impacts? Or is it more realistic to promote deep expertise in sections of this sequence, an awareness of the need to collaborate with others more steeped in other sections, and to attempt to design effective coordinative mechanisms to manage the handoffs?
      It seems unlikely that the former model can realistically be achieved. Aside from the training costs associated with providing all of the necessary expertise, interests among investigators vary. Some are far more interested in physiological systems than in human functioning, and vice versa. Insisting that each investigator have all of these interests and skills simply narrows the number of people that can work in research. Moreover, even if this could be achieved, it would be an inefficient model. Imagine, for example, separate investigative teams studying 3 different treatments that enhance muscle strength: voluntary progressive resistance exercises, electrical simulation-based muscle exercises, and injection of muscle trophic factors. Under the fully longitudinal model, each of these teams would be expected to first optimize their treatment and then develop complex enablement models of gait in order to explore the clinical translation of their treatments. However, enablement models are unconcerned about how a change in strength is brought about. If all 3 of these treatments effectively enhance muscle strength, then their distal clinical impacts will be predicted to be the same; there is no advantage to development of separate enablement models for each treatment. This perspective suggests not only that a handoff could occur, but that it should occur. Of course, that is still a far cry from explaining how such a handoff could be ensured and managed—a simple “treatment theory-focused researchers and enablement theory-focused investigators should talk” will not do it.
      This problem is not limited to the development of rehabilitation treatments. Pharmaceutic research goes through formalized developmental phases, beginning with testing in tissue and animal models, progressing to human safety testing, and then moving to clinical efficacy assessment.

      The Independent Institute. The drug development and approval process. Available at: http://www.fdareview.org/approval_process.shtml. Accessed November 29, 2012.

      In the case of new drug development, however, the corporate developer has an incentive to manage the movement from basic scientists to clinical trial experts. Nevertheless, much has been written about the challenges to general translational research and the tendency for treatments under development to stall at similar points of hand-off.
      • Sung N.S.
      • Crowley Jr., W.F.
      • Genel M.
      Central challenges facing the national clinical research enterprise.
      The National Institutes of Health has funded a series of clinical and translational science awards, which are structured to promote translational maturation of treatments.

      National Center for Advancing Translational Sciences. About the CTSA program. Available at: http://www.ncats.nih.gov/research/cts/ctsa/about/about.html. Accessed November 29, 2012.

      Research Funding

      Funding for clinical research is challenging to obtain, and funding agencies are fundamentally conservative, wanting a fair degree of assurance that funds will result in useful outcomes. Much clinical rehabilitation research, consequently, must strike a difficult balance in addressing treatment theory and enablement theory. A study strongly grounded in treatment theory may choose a measure of the treatment target as the primary outcome because this is, after all, the purest assessment of the treatment theory itself. However, this may be criticized by grant reviewers as not clinically relevant if the outcome measure is not itself functionally significant. In contrast, an investigator who seeks to satisfy reviewers by choosing more macro and clinically important outcomes may be criticized because there are so many unrelated reasons (ie, other confounding impairments or activity limitations) that a treated patient may fail to achieve those outcomes.
      In order to optimize the payoff from society's investment in research, changes are required on the parts of both rehabilitation investigators and funding agencies. Investigators need to learn to write clearly about the sequence of stages that will ultimately be required to generate clinically meaningful treatment impact, and about the precise contribution their proposed research makes to movement along that sequence. On the other side, grant reviewers and funding agencies need to understand that not every study should be held to a standard of clinically meaningful impact. Such a phase of research is needed, but it is more likely to succeed after the impact of the new treatment on its target has been maximized and if careful attention is given to defining the kind of patient most likely to experience clinically meaningful impact of the treatment after consideration of enablement complexities. It is gratifying to see that the National Institute on Disability and Rehabilitation Research, in the draft of its most recent long range plan, acknowledges the concept of stages of development of rehabilitation treatments.

      Office of Special Education and Rehabilitative Services, Department of Education. National Institute on Disability and Rehabilitation Research; notice of proposed long-range plan for fiscal years 2013-2017. Available at: http://www.gpo.gov/fdsys/pkg/FR-2012-04-18/html/2012-9365.htm. Accessed December 4, 2012.

      Clinical Education

      The concepts discussed here are not new to the clinical discourse. Clinical trainees are often asked by their supervisors to articulate the empirical evidence that a treatment is effective or to provide a hypothetical rationale for a treatment's predicted impact. Clinical trainees are also often challenged with questions such as, “Well, this treatment may work, but will it have any functional impact?” Although these questions roughly correspond to treatment theory and enablement theory issues, these kinds of queries are not often clearly differentiated. In particular, the fact that the first question pertains to the nature of a treatment, but the second question really pertains to the relation between a person and an activity, is not appreciated. That is, a question about the relation between spasticity and active movement is relevant to treatment, but it is relevant to all potential treatments of spasticity, not to the specific treatment being discussed.
      Therefore, sharpening the distinction between these 2 classes of theories can also support more analytic clinical thinking. In many cases, rehabilitation treatments are neither effective nor ineffective, but are effective in some patients but not in others, because of different patterns of strengths and deficits in these patients. Appreciating the distinction between treatment and enablement theory helps clinicians identify those treatments that have empirical support for altering their desired target (ie, efficacious with respect to the treatment target), and those patient characteristics that identify who will experience clinical benefit from those treatments (ie, as guided by enablement theory). Continued research on each domain and on their interrelation will ultimately enhance clinical education.

      Conclusions

      Attention has been drawn previously to the importance of theory in advancing scientific research, and rehabilitation treatment research in particular.
      • Keith R.A.
      The role of treatment theory.
      • Whyte J.
      Directions in brain injury research: from concept to clinical implementation.
      • Whyte J.
      • Barrett A.M.
      Advancing the evidence base of rehabilitation treatments: a developmental approach.
      • Whyte J.
      A grand unified theory of rehabilitation (we wish!). The 57th John Stanley Coulter Memorial Lecture.
      • Hart T.
      Treatment definition in complex rehabilitation interventions.
      • Whyte J.
      Using treatment theory to refine the designs of brain injury rehabilitation treatment effectiveness studies.
      • Whyte J.
      • Hart T.
      It's more than a black box, it's a Russian doll: defining rehabilitation treatments.
      Theory-guided research is particularly challenging in rehabilitation because of the wide range of domains that is addressed by rehabilitation and the correspondingly diverse set of theories that is relevant. Organizing the relevant theoretical perspectives into 2 broad classes (treatment theories and enablement theories) can, however, lend some order to this chaos. These different forms of theory address fundamentally different issues on how to induce change and how to predict the distal impacts of that change. Understanding their separate contributions and learning how to navigate them jointly can advance clinical education, research, and practice.

      Acknowledgments

      I thank Tessa Hart, PhD, for providing ongoing guidance in the development of the ideas expressed here and Marcel P. Dijkers, PhD, FACRM, Mary Ferraro, PhD, OTR/L, Andrew Packel, MSPT, Jeanne M. Zanca, PhD, MPT, and Theodore Tsaousides, PhD, for critical discussion of this article. I also thank Mary Czerniak for assistance in its preparation.

      Supplemental Appendix S1 Glossary of Terms

      Active ingredients – Attributes of a treatment, selected or delivered by the clinician, that play a role in the treatment's effects on the target of treatment. These include the essential ingredients associated with the treatment's known or hypothesized mechanism of action, and any other ingredients that moderate the treatment's effect(s) but may be common to multiple treatments.
      Aim(s) (of treatment) – Aspect(s) of the patient's or other recipient's functioning or personal factors that is predicted to change indirectly (via mechanisms specified in enablement/disablement theory) as a result of the treatment-induced change in the treatment target. A single treatment may have multiple aims, and there may be a chain of treatment aims (eg, exercises leading to increased strength leading to improved ambulation leading to greater community participation) with at least 1 (in the case of treatments delivered to other recipients) involving the patient's functioning. Although highly relevant to the ultimate clinical value of a treatment, these distal treatment aims are not relevant to the definition or classification of the treatment. (As previously noted, when the target of treatment is clinically and functionally significant in its own right, we avoid calling it a treatment aim to avoid confusion about direct vs indirect effects of treatment.)
      Course of treatment – Series of treatment sessions or therapist-recipient contacts that are pursuing change in a specific treatment target, sometimes with some form of treatment progression within or between contacts.
      Dosing parameters – Quantitative variations in the strength, intensity, frequency, and/or quantity of treatment ingredients; these are often expressed as an amount of time during which the recipient is continuously exposed to the ingredient, the number of times a discrete ingredient is administered, or the magnitude of the ingredient on a quantifiable scale.
      Enablement/disablement theory – Conceptual system that specifies how change in one aspect of a patient's functioning (eg, at the level of an International Classification of Functioning, Disability and Health component: body structure, body functioning, activity/activity limitation, participation/participation restriction, personal factor, or environment) will translate into changes in another aspect, specifically a characteristic classified elsewhere in the framework being used.
      Essential ingredients (of a treatment) – Active ingredients, selected or delivered by the clinician, that define a particular treatment and distinguish it from other treatments. The essential ingredients are those that are specified by the corresponding treatment theory, and are hypothesized or known to be necessary for the treatment's effects on the treatment target.
      Inactive ingredients (of a treatment) – Attributes of a treatment that do not define or moderate the impact of the treatment on the target. Ingredients may be presumed to be inactive because they are not addressed by a treatment theory (eg, the building in which the treatment is conducted) or have been empirically determined to be inactive.
      Ingredients – See Treatment ingredients.
      Mechanism of action – Process by which the treatment's essential ingredients induce change in the target of treatment. A treatment theory should specify how the essential ingredients engage mechanisms of action to bring about desired treatment effects, that is, specification of the mechanism of action explains how the essential ingredients alter the treatment target within the framework of the treatment theory. Similarly, additional mechanisms of action specify how other active ingredients moderate the effects of the treatment.
      Nonvolitional treatments – Treatments whose hypothesized mechanisms of action require no effort on the part of the recipient (other than cooperation/nonresistance). Unlike volitional treatments (subsequently defined), the recipient of nonvolitional treatment is always the patient/client undergoing rehabilitation, not a third party (eg, caregiver).
      Patient/client – Person with a disability or at risk of a disability who is the intended beneficiary of treatment.
      Progression - Clinician's deliberate, systematic alteration of the treatment to maintain, over time, the degree of challenge to the body system/behavior(s) selected for change. Progression is often triggered by improvements in the target of treatment; therefore, the pace of progression (within a single treatment contact or a course of treatment) typically depends on the pace of change in the treatment target. The form that treatment progression takes (and hence the nature of the challenge that is being maintained) is often specified by the treatment theory; therefore, multiple treatment sessions may need to be observed to distinguish between one treatment and another.
      Recipient (of treatment) – Individual whose function/behavior is intended to be changed directly as a result of treatment. In most cases this is the person with a disability (patient/client recipient), but in some instances a caregiver or employer may be the other recipient who is changed by the intervention (eg, to provide care or intervention to the patient/client or to create a more supportive environment for the patient/client).
      Rehabilitation treatment taxonomy – System of classifying rehabilitation treatments based on a principle or set of principles that allows for distinctions between treatments, which have practical and/or theoretical utility.
      Session (of treatment) – Individual episode of treatment (typically minutes to a few hours), which may be repeated during a course of treatment.
      Target of treatment/treatment target – Aspect of the recipient's functioning, or personal factor, that is predicted to be directly changed by the treatment's mechanism of action. Specification of the target of treatment in a theory in terms of an International Classification of Functioning, Disability and Health variable(s) helps to define the scope of the treatment/treatment theory. (The aim of treatment refers to changes in functioning obtained in indirect ways—see Aim(s) (of treatment), above. Although there are instances where the target of treatment is functionally important in its own right, without reference to distal enablement effects, we nevertheless reserve the term treatment aim only for the functionally relevant clinical effects that are distal to the treatment target.)
      Taxonomy – System of classification or categorization based on characteristics that have important pragmatic or theoretical implications.
      Treatment – Action taken by a health professional, in the context of contact with a treatment recipient, to alter the functioning of an individual with a disability or at risk of a disability. Treatment is defined broadly to include provision of information, devices, and referrals, specific active experiences, and passive interventions.
      Treatment grouping – Broad class of treatments that is similar in essential ingredients (eg, forms of energy) and is able to act on a class of similar treatment targets (eg, tissue properties).
      Treatment ingredients – Observable (and, therefore, in principle, measurable) actions, chemicals, devices, or forms of energy that are selected or delivered by the clinician. See also Active ingredients, Dosing parameters, Essential ingredients, and Inactive ingredients.
      Treatment theory – Conceptual system that predicts the effects of specific forms of treatment on their targets, specifying the law(s) that expresses the relations between essential ingredients and treatment target changes. (This is similar to Mechanism of action but may be broader and more inclusive.)
      Volitional treatments – Treatments where a hypothesized mechanism(s) of action requires some effort on the part of the treatment recipient.

      References

      1. World Health Organization. International Classification of Functioning, Disability and Health (ICF). Available at: http://www.who.int/classification/icf. Accessed November 30, 2012.

        • Keith R.A.
        The role of treatment theory.
        in: Fuhrer M.J. Assessing medical rehabilitation practices: the promise of outcomes research. Paul H. Brookes, Baltimore1997: 257-274
        • Lipsey M.W.
        Theory as method: small theories of treatment.
        in: Sechrest L. Perrin E. Bunker J. Research methodology: strengthening causal interpretations of nonexperimental data. Agency for Health Care Policy and Research, Public Health Service, U.S. Department of Health and Human Services, Washington (DC)1990: 33-51
        • Whyte J.
        Directions in brain injury research: from concept to clinical implementation.
        Neuropsychol Rehabil. 2009; 19: 807-823
        • Whyte J.
        • Barrett A.M.
        Advancing the evidence base of rehabilitation treatments: a developmental approach.
        Arch Phys Med Rehabil. 2012; 93: S101-S110
        • Whyte J.
        A grand unified theory of rehabilitation (we wish!). The 57th John Stanley Coulter Memorial Lecture.
        Arch Phys Med Rehabil. 2008; 89: 203-209
        • Whyte J.
        • Gordon W.
        • Rothi L.J.
        A phased developmental approach to neurorehabilitation research: the science of knowledge building.
        Arch Phys Med Rehabil. 2009; 90: S3-10
        • Dijkers M.P.
        • Hart T.
        • Tsaousides T.
        • Whyte J.
        • Zanca J.M.
        Treatment taxonomy for rehabilitation: past, present and prospects.
        Arch Phys Med Rehabil. 2014; 95: S6-S16
        • Locke E.A.
        • Latham G.P.
        Building a practically useful theory of goal setting and task motivation.
        Am Psychol. 2002; 57: 705-717
        • Whyte J.
        Assessing medical rehabilitation practices: distinctive methodologic challenges.
        in: Fuhrer M. The promise of outcomes research. Brookes, Baltimore1997
        • MacKay-Lyons M.
        Low-load, prolonged stretch in treatment of elbow flexion contractures secondary to head trauma: a case report.
        Phys Ther. 1989; 69: 292-296
        • Hart T.
        • Evans J.
        Self-regulation and goal theories in brain injury rehabilitation.
        J Head Trauma Rehabil. 2006; 21: 142-155
        • Sullivan K.J.
        • Cen S.Y.
        Model of disablement and recovery: knowledge translation in rehabilitation research and practice.
        Phys Ther. 2011; 91: 1892-1904
        • Whyte J.
        Mechanisms of recovery of function following CNS damage.
        2nd ed. FA Davis, Philadelphia1989
        • Hart T.
        Treatment definition in complex rehabilitation interventions.
        Neuropsychol Rehabil. 2009; 19: 824-840
        • Whyte J.
        Using treatment theory to refine the designs of brain injury rehabilitation treatment effectiveness studies.
        J Head Trauma Rehabil. 2006; 21: 99-106
        • Whyte J.
        • Robinson K.
        Pharmacological management of spasticity.
        in: Glenn M.B. Whyte J. The practical management of spasticity in children and adults. Lea and Febiger, Philadelphia1990: 201-226
        • Tinetti M.E.
        Preventing falls in elderly persons.
        New Engl J Med. 2003; 348: 42-49
      2. The Independent Institute. The drug development and approval process. Available at: http://www.fdareview.org/approval_process.shtml. Accessed November 29, 2012.

        • Sung N.S.
        • Crowley Jr., W.F.
        • Genel M.
        Central challenges facing the national clinical research enterprise.
        JAMA. 2003; 289: 1278-1287
      3. National Center for Advancing Translational Sciences. About the CTSA program. Available at: http://www.ncats.nih.gov/research/cts/ctsa/about/about.html. Accessed November 29, 2012.

      4. Office of Special Education and Rehabilitative Services, Department of Education. National Institute on Disability and Rehabilitation Research; notice of proposed long-range plan for fiscal years 2013-2017. Available at: http://www.gpo.gov/fdsys/pkg/FR-2012-04-18/html/2012-9365.htm. Accessed December 4, 2012.

        • Whyte J.
        • Hart T.
        It's more than a black box, it's a Russian doll: defining rehabilitation treatments.
        Am J Phys Med Rehabil. 2003; 82: 639-652