By John W. A. Osborne, PhDc; Hylton B. Menz, PhD, DSc, BPod(Hons); Glen A. Whittaker, PhD, BPod(Hons); and Karl B. Landorf, PhD
Addressing associated reduced muscle function and strength may improve treatment outcomes for plantar heel pain.
People with plantar heel pain (PHP) have reduced foot and ankle muscle function, strength, and size, which is frequently treated by muscle strengthening exercises. However, there has been little investigation of what exercises are used and there is no sound evidence base to guide practice. This study aimed to develop a consensus-driven progressive muscle strengthening program for PHP.
Methods
Thirty-eight experts were invited to participate in the study over 3 rounds. Round 1, an open-ended questionnaire, provided the core characteristics of progressive strengthening programs designed for 3 different adult patient types with PHP (younger athletic, overweight middle-aged, older), which were presented as vignettes. In Round 2, experts indicated their agreement to the proposed exercises and training variables. In Round 3, experts were presented with amendments to the exercises based on responses from Round 2 and indicated their agreement to those changes. Consensus was achieved when > 70% of experts agreed.
Results
In total, 24 (67%) experts participated in Round 1. Eighteen (75%) completed all 3 rounds. From Round 1, progressive strengthening programs were developed for the 3 vignettes, which included 10 different exercises and 3 training variables (sets/repetitions, weight, frequency). In Round 2, 68% (n = 17) of exercises and 96% (n = 72) of training variables reached consensus. In Round 3, only exercise changes were presented and 100% of exercises reached consensus.
Exercise prescription
Twenty-two (92%) respondents stated they would prescribe a progressive foot strengthening program for PHP. The 2 respondents who indicated they would not prescribe such a program agreed they would use a reloading strategy in the right circumstances:
Strength training goals, indications, and contradictions
Seven themes were extracted regarding the goals of strength training exercises for PHP: addressing muscle weakness (n = 7), increasing tissue load/capacity (n = 6), reducing strain to the plantar fascia (n = 4), improving impact absorption of the foot (n = 3), improving function (n = 2), reducing arch deformation (n = 2), and reducing pronation (n = 1).
The 2 most common responses regarding indications for a progressive strengthening program were that it can be applied to all patients (n = 6) and to athletic or physically active individuals (n = 4). Only 3 contraindications were raised: the presence of a neurological (n = 1), bone (n = 1), or fat pad (n = 1) pathology.
Exercise selection, muscles to be targeted, movement concepts
The most common exercises were heel raise variations (n = 10), digital plantarflexion (n = 8), and the short foot exercise (n = 8). The most common muscles to be targeted were foot intrinsics as a group (n = 6). Specific muscles mentioned included: calf (n = 2), flexor hallucis longus (n = 2), flexor digitorum brevis (n = 1), flexor digitorum longus (n = 1), tibialis posterior (n = 1), and adductors (n = 1)—although not defined as hip or foot adductors. Three themes emerged as movement concepts rather than specific exercises to be prescribed: applying a talar neutral position (n = 3), foot core (n = 1), and toe posture (n = 1).
Dosage variables, progression of exercise
The most common dosage variable used was sets and repetitions (n = 14), followed by achieving a repetition maximum (n = 3), and time under tension (n = 2). The most common number of sets and repetitions was 3 (n = 5), 4 (n = 3), and 5 (n = 3) and 10, 12, and 15 (n = 5), respectively. The most common responses for progressing difficulty of exercise were to increase volume (n = 8), weight (n = 5), and complexity (n = 3).
Round 2
A 3-stage progressive strengthening program was derived from the results of Round 1 for each vignette. Eighteen (75%) experts completed Round 2, although 1 completed only the first vignette.
Younger athletic adult
Seven of 9 (78%) exercises achieved consensus. The exercises that did not achieve consensus were heel raise seated with digits dorsiflexed (67%) and short foot exercise while standing (67%). Twenty-six of 27 (96%) exercise training variables met consensus. The heel raise seated with digits dorsiflexed did not reach consensus for frequency of exercise (daily).
Overweight middle-aged adult
Five of 8 (63%) exercises achieved consensus. The exercises that did not achieve consensus were towel scrunch with inversion and eversion (59%), single leg standing on an unbalanced surface (53%), and short foot exercise seated (59%). Twenty-two of 24 (92%) exercise training variables reached consensus.
Older adult
Five of 8 (63%) exercises achieved consensus. The exercises that did not achieve consensus were towel scrunches (53%), towel scrunch with inversion and eversion (41%), and short foot exercise while seated (65%). All 24 exercise training variables reached consensus.
Progressions
The progressions of exercises and stages of the program did not reach consensus, with just 54% agreement. The progressions were based on increasing repetitions first, as follows: ‘Each week the program progresses by adding 2 repetitions and keeping the weight and other variables the same. All participants begin on Stage 1 of the exercise regime. If there is no perceived difficulty or pain, then progression to Stage 2, and so on for Stage 3.’
Round 3
All 18 experts completed Round 3. The exercises that did not reach consensus in Round 2 were replaced in Round 3 with the exercises that were suggested most frequently by the experts in Round 2. For example, the towel scrunch with inversion and eversion did not meet consensus in Round 2 for the older adult (41%), so it was replaced with short foot exercise seated, which was the most frequently suggested replacement exercise. Following these replacements, all 3 progressive strengthening programs met consensus in Round 3.
Progressions
Exercise progressions were updated to increase weight and then functionality, rather than increase repetitions first, in response to expert feedback in Round 1. This progression strategy achieved 100% consensus. The final progressive strengthening programs are presented in Table 1.
Discussion
Three exercises were consistently recommended throughout the study: heel raises, digital plantarflexion, and the short foot exercise, albeit with significant variation in how they were described and applied. Heel raises were the most commonly suggested exercise. However, a recent systematic review found that there is no difference in heel raise capacity between those with and those without PHP, so this recommendation may diverge from current evidence. Interestingly, both the heel raise and the heel raise with the digits dorsiflexed exercise variation were occasionally not recommended by some experts due to perceived difficulty or provocation of symptoms, indicating the need to better understand the role of exercises for PHP. Further, there is little robust evidence for the benefit of the exercise selections for those with PHP. Additionally, further research evaluating the effectiveness of increases in weight (within each stage of the progressive strengthening program) and functionality (between individual stages of the program) would be beneficial.
Conclusion
This study provides 3 progressive strengthening programs agreed to by experts that can be used in future clinical trials to determine the effectiveness of muscle strengthening for PHP. In addition, clinicians could use the programs as part of a rehabilitation strategy with the caveat that they may change as more research is conducted.
John W. A. Osborne, PhD candidate in the discipline of podiatry, La Trobe University, Melbourne, Australia. He also has a clinical role as head of podiatry in private practice at a sports medicine clinic in the eastern suburbs of Melbourne, Australia.
Hylton Menz, PhD, DSc, BPod(Hons), is a professor with La Trobe University, School of Allied Health, Human Services and Sport, Melbourne, Australia.
Glen A. Whittaker, PhD, BPod(Hons), is a senior lecturer and early career researcher with a clinical and academic background in podiatry with La Trobe University, School of Allied Health, Human Services and Sport, Melbourne, Australia, he is also in private practice with Fitzroy Foot and Ankle Clinic, Fitzroy North, Australia.
Karl B. Landorf, PhD, is a professor of podiatry and associate dean, Research and Industry Engagement in the School of Allied Health, Human Services and Sport at La Trobe University, Melbourne, Australia.
This article has been excerpted from “Development of a foot and ankle strengthening program for the treatment of plantar heel pain: a Delphi consensus study,” which appeared in the Journal of Foot & Ankle Research; 2023;16:67. https://doi.org/10.1186/s13047-023-00668-2. Editing has occurred, including the renumbering or removal of tables, and references have been removed for brevity. Use is per CC 4.0 International Licenses.
