Exercise Prescription: The Devil Is in the Details

Editor's Note: Commentary based on Abell B, Glasziou P, Hoffmann T. Reporting and replicating trials of exercise-based cardiac rehabilitation: do we know what the researchers actually did? Circ Cardiovasc Qual Outcomes 2015;8:187-94.

When the outcomes of clinical trials are released, many health care providers ask themselves, "Definitely another great trial, but how will I ever be able to apply it in my practice?"

The incomplete descriptions of therapeutic interventions have limited the translation of reported findings of clinical trials into daily clinical practice. Similarly, the incomplete descriptions of therapeutic interventions have impeded guideline development. In their systematic review, Abell et. al. examine the reporting quality of 57 eligible randomized controlled trials of exercise-based cardiac rehabilitation published between 1975 and December 2013.1 A complete detailed description of protocols during exercise-based cardiac rehabilitation is necessary for providers wishing to apply this non-pharmacological, multidisciplinary intervention with demonstrated efficacy in the secondary prevention of coronary artery disease, as well as mortality and hospitalization reduction in stable heart failure patients.2 These 57 studies were scrutinized according to the Template for Intervention Description and Replication (TIDieR) guide and checklist,3 looking for completeness in the reporting of the 12 items of the template (name of the intervention, rationale behind it, materials provided, procedures, provider, mode of delivery, location, dose/schedule, individualized tailoring, modifications during intervention, and strategies to maintain fidelity and adherence).

The data is striking. Only 8% of the trials had complete reporting of the protocol used during cardiac rehabilitation in the original manuscripts; this number increases to 15% when additional supplements to the publication are reviewed. The authors then attempted to contact individual trial authors asking for the missing information. This tedious and time-consuming process resulted in an increase in the rates of completeness to 43%. Twenty authors (30%), mostly those who authored publications over 15 years old, were not possible to reach despite multiple attempts. While many believe that the quality of clinical trials has been improving in recent years, the authors interestingly noted similar rates of incomplete reporting in trials done throughout the last 4 decades.

Actions to improve this reporting deficiency problem can be taken on multiple levels to address this quality issue of primordial importance. The main trial manuscript word limit, a commonly cited reason for incomplete reporting, can be easily overcome by the possibility to add intervention data via online supplements, which is provided free of charge in most indexed journals. While it is the duty of the authors to fully report all aspects of any intervention, the journal editors, peer reviewers and institutional review board committees should assess for completeness by following the TIDier guide when reviewing any trial protocol or reports, prior to publication.

The authors end their manuscript with a call for improvement in the quality of reported trials of exercise-based cardiac rehabilitation in order to facilitate the delivery of evidence-based care in this growing field.

The implications of this study extend beyond the translation of reported trial results into common clinical practice. While many cardiologists appreciate the benefit of exercise for the primary and secondary prevention of cardiovascular disease, effective translation of this belief requires more than simply telling patients to "exercise" or "exercise several days a week." Proper implementation of exercise guidelines in clinical practice requires that exercise be prescribed for patients in a manner analogous to a drug prescription. Physicians regularly prescribed drugs by enumerating the drug name, the dosage, the dosage frequency, and often the time of administration. Exercise can and should be prescribed with enough detail to allow the patient, either alone or with the aid of non-physician staff (e.g., cardiac rehabilitation), to engage in an exercise regimen that has been proven to be both safe and beneficial. A useful framework for exercise prescription is the acronym FITT: Frequency, Intensity, Time, and Type. For example, a patient may be prescribed an every-other-day (frequency), moderate-intensity (intensity judged by HR or perceived intensity), 20-minute (time) walking (type) regimen. Similarly, a patient may be prescribed strength training twice weekly (frequency) 5-pound (intensity) 12-repetition (time) dumbbell biceps curl (type). Including specific details in recommendations and instructions when prescribing exercise for patients will enhance the likelihood of their engaging in safe and effective exercise. Exercise is medicine!

A simplified FITT table is listed (Table 1).

Table 1


Cardio Exercise

Strength Exercise


5 days/week – Moderate intensity*
3 days/week – High Intensity**
P.S. Increase to 6 or 7 days if aiming at weight loss

2 to 3 non-consecutive days/week


Exercise in target heart rate***
Focus on variety of intensities

Determined by the amount of weight lifted and the reps and sets
Goal of 8-10 exercises, around 1-3 sets of 8-16 reps of each exercise


30 to 60 minutes/session - Shorter if exercise is high intensity

Depends on strength and schedule: up to 1 hour for total body workout, less for split routine workup


Any activity that increases heart rate: running, walking, cycling, dancing...

Activities using resistance: bands, dumbbells, machines, bodyweight exercise

*Moderate Intensity: 50-69% of target heart rate
**High Intensity: 70-less than 90% of target heart rate
***Target Heart Rate: Table 2 below shows estimated target heart rates for different ages. Maximum heart rate used to be estimated at about 220 minus the age, although a more accurate formula, offered in a study published in Medicine & Science in Sports & Exercise is 206.9 - (0.67 x age).4

Table 2


Target HR Zone 50-85%

Average Maximum Heart Rate, 100%

20 years

100-170 beats per minute

200 beats per minute

30 years

95-162 beats per minute

190 beats per minute

35 years

93-157 beats per minute

185 beats per minute

40 years

90-153 beats per minute

180 beats per minute

45 years

88-149 beats per minute

175 beats per minute

50 years

85-145 beats per minute

170 beats per minute

55 years

83-140 beats per minute

165 beats per minute

60 years

80-136 beats per minute

160 beats per minute

65 years

78-132 beats per minute

155 beats per minute

70 years

75-128 beats per minute

150 beats per minute


  1. Abell B, Glasziou P, Hoffmann T. Reporting and replicating trials of exercise-based cardiac rehabilitation: do we know what the researchers actually did? Circ Cardiovasc Qual Outcomes 2015;8:187-94.
  2. O'Connor CM, Whellan DJ, Lee KL, et al. Efficacy and safety of exercise training in patients with chronic heart failure: HF-ACTION randomized controlled trial. JAMA 2009;301:1439-50.
  3. Hoffmann TC, Glasziou PP, Boutron I, et al. Better reporting of interventions: template for intervention description and replication (TIDieR) checklist and guide. BMJ 2014;348:g1687.
  4. Jackson AS. Estimating maximum heart rate from age: is it a linear relationship? Med Sci Sports Exerc 2007;39:821.

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