On the Merits of Targeted and Individualized Physical Exercise in Persons with Diabetic Foot Disease – from Controversies to Consensus

1. Introduction

Exercise is the basis of diabetes (DM) treatment [1,2,3], as physical activity (PA) plays an important role in regulating glucose levels in the body [4,5,6,7]. Therefore undertaking activity by patients is recommended by all scientific societies dealing with the issue of carbohydrate metabolism disorders.

According to the definition of International Working Group on the Diabetic Foot (IWGD) [8], it is a condition when a patient with diabetes and neuropathy and/or arterial blood flow disorders in the lower limbs develops: ulceration, infection and/or destructive changes in the deep tissues below the ankle. There is ample evidence that targeted PA (exercise) reduces the risk of such a complication (prevention stage) [9]. Adequate exercise improves sole load distribution, skin sensitivity, peripheral nerve conduction, intraepidermal nerve fibre density or joint mobility of the foot which translates into proper gait [10,11] and reduces the risk of pathologies typical of diabetes occurring in that area [12,13,14,15,16,17,18,19,20]. As in patients without diabetes, walking has a beneficial effect on peripheral circulation, reducing the risk of clinically significant limb ischemia leading to ulcers and amputations [21,22,23]. At the prevention stage, patients are educated about the role of exercise and its safety. The condition of the peripheral nervous system (perception of injury) and blood supply to the limbs is assessed.

In some cases, due to overlapping diseases, patients are advised to discontinue or limit their current activities for the duration of treatment, which may have adverse effects not only on patients' glycemic control (increase in insulin resistance) and body weight but also on respiratory and cardiovascular systems as well as contribute to musculoskeletal disorders, which translates into delayed recovery and poorer functioning after recovery [24,25,26,27,28,29,30,31]. An example of such a situation in the life of a patient with DM is the occurrence of diabetic foot disease (DFD).

In the case of the presence of an unhealed ulcer, current guidelines on the treatment of diabetes and its complications provide only the recommendation to eliminate weight-bearing activity [32,33] In the presence of Charcot deformity, the role of stretching and muscle-strengthening exercises is noted as potentially helpful [32]. In the Clinical Practice Guideline published in 2023 [34] the authors address this issue and explicitly raise the problem of “Various fitness/exercise routines with various intensities, including aerobic and resistance training” in the context of an expected outcome defined as: “Improved mobility in the context of wound healing.” However, even in this document, the lack of precise recommendations regarding which exercises should be prescribed and what their potential benefits are is emphasized. Similarly, in the IWGDF guidelines [33] - the most authoritative document in this field- 29 recommendations are provided for managing DFD, but none of them refer to exercise. This situation results from the limited number of RCTs (Randomized Controlled Trials) dedicated to this topic that have included a sufficiently large number of patients in the intervention.

The aim of the article is to highlight the role that exercise, when performed with individualized precautions, can play in improving the condition of a patient with a wound and/or foot deformity due to diabetic foot disease.

2. Methodology

The foundation of our narrative review article is a comprehensive systematic review published in 2023 [35], which summarized the limited but growing body of clinical research focused on exercise interventions initiated after a diagnosis of DFD. This review highlighted the potential benefits of various exercise modalities based on the available studies. Following its publication, a new randomized clinical trial was released [36], further supporting the inclusion of exercise in the management of patients with DFD—although it has not yet influenced clinical guidelines [32,33].

In addition to the available clinical studies discussed in the mentioned systematic review and new data from 2024, we incorporated findings from basic research, including preclinical experiments (on animals and humans), which provide mechanistic insights into how even simple physical exercises may contribute to both local and systemic improvements in individuals with DFD.

Until more large-scale, high-quality trials become available, clinicians may consider relying on the current evidence from both basic and clinical research to guide individualized therapeutic decisions.

The authors of the publication have medical (diabetology: ES, AK-B, vascular: ES diseases) and physiotherapeutic (ES, KB) backgrounds, as well as many years of experience in treating patients with diabetic foot disease.

3. Results

3.1. The Role of Exercise in Patients with Active Diabetic Foot Disease

In the event of a complication such as diabetic foot, the primary goal achieved through appropriate pharmacotherapy is: control of glycemia, correction of other risk factors (cholesterol level and blood pressure values), use of antiplatelet drugs, sometimes low doses of anticoagulants (applies to treatment of limb ischemia) and, in justified cases, administration of antibiotics and painkillers.

Treatment includes revascularisation (for vascular lesions), removal of dead tissue, orthopaedic procedures to correct foot deformity or, supportively, physical therapy procedures [8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,37].

Regardless of the above, however, the essential recommended management of ulceration, deformation and deep tissue inflammation in DFD is the offloading of the affected area [38,39,40]. The purpose is not to expose damaged tissues to further injury and to create conditions for healing by, e.g., eliminating the pressure forces in the tissues of the foot, arising in the situation of loading. The recommendation to offload is often associated with immobilisation of the patient or significant restriction of their activity (to essential activities) [38,39], which is also determined by the way in which offloading is achieved: wheelchair, elbow crutches, special footwear or total contact cast (TCC).

Thus, in the described case, a conflict of recommendations arises. On the one hand, local changes require offloading, which means avoiding walking and standing [41], on the other hand, local changes, such as inflammation, generate an increase in glycemia per se and activity restriction promotes that increase and hinders healing. In addition, lack of exercise reduces muscle mass and deteriorates blood supply to the wound area and its bottom. This is a significant issue as proper blood supply is fundamental to wound healing [21,22].

Lack of muscle contraction and joint flexion (natural activities when walking) can cause swelling, which further impedes microcirculatory flow and stiffens joints reducing their range of motion (ROM). Prolonged inflammation can lead to bone resorption due to local vasodilation [42]. Chronic immobilisation also promotes the development of osteoporosis. Each of those disorders has an adverse local impact but also worsens many of the patient's functions [26,27,28,29,30,31].

Meanwhile, the benefits of exercise are local and general [43,44,45]. Studies confirm that PA in diabetes has beneficial effects on the cardiovascular system [46,47], microcirculation [48,49] or kidneys [50], which is not without significance taking into account the fact that the correlation between chronic complications and cardiovascular risk has been known for years. Improvements in insulin sensitivity, the patient's functional and psychological state and quality of life are also the effects of targeted activity, i.e. exercise [51]. Therefore, exercise is necessary for the patient not only in the phase of preventing complications but also when they have already appeared. The essence of the appropriate approach is to implement exercises in a planned manner.

Last year, an expert position was published [52], summarising recommended actions for DFD. They include an assessment of the usefulness of exercises that the patient may undertake during the treatment of the condition in question. While emphasising the lack of sufficient evidence that exercise directly accelerates wound healing, the authors recommend performing some of them due to the potential benefits demonstrated in animals [53,54] and humans [55].The rather modest work on the subject of exercise by patients with diabetic foot to date is supplemented by the recent report [36], released after the publication of the above-mentioned document. The condition for undertaking exercises is to adhere to the principle of relieving the local change and its surrounding area.

3.2. The Effect of Exercise on the Local Condition in Diabetic Foot Disease

Long-term offloading can provoke local osteoporosis and also generate it in other areas of the relieved limb [56]. Local inflammation may also contribute to that, due to increased flow in the microcirculation.

The implementation of properly selected exercises can be helpful and have measurable benefits [57,58], preventing further reduction in bone mineral density (BMD), having a beneficial effect on glycemic control and the patient's well-being [31]. Even local inflammation [59] causes oxidative stress, which disrupts the repair processes in the wound and has an adverse effect on the entire body, which translates into, e.g., increased insulin resistance and, consequently, increased glycemia. That triggers a vicious cycle mechanism as normalisation of glycemia is necessary for wound healing. The changes taking place during local infection and their consequences are comprehensively described by Huang H. et al [60]. There is data supporting the impact of exercise on the reduction of the severity of local inflammation, regardless of other standard actions taken in this regard [61,62,63,64,65]. This is due to mechanisms activated during exercise, which limit the production of pro-inflammatory cytokines and increase the secretion of anti-inflammatory myokines. The latter also enhances local angiogenesis [66,67]. Exercise is an important part of improving glycemia, playing an important role in making the local condition better [23]. In a hyperglycemic environment, the activity of antioxidant enzymes is reduced, the number of advanced glycation end products (AGEs) increases, which enhances the hypoxia of local tissues, which is further intensified by oxygen-consuming pathogens (in the case of infection) and inflammatory cells [60]. High glycemia inhibits the proliferation and differentiation of fibroblasts, impairs the secretion of transforming growth factor-β (TGFβ) and reduces collagen synthesis [67]. Additionally, in such an environment, the activity of endothelial nitric oxide synthase (eNOS) is inhibited, which leads to vascular damage [68]. Hyperglycemia and vascular damage are thus closely related.

Various forms of planned activity such as Buerger exercises [69,70,71], exercises improving ROM or stretching [19,37] contribute to improving local circulation, which creates better conditions for the healing of changes in the foot. Additionally, improving the ROM is important for the patient's future [72,73] as its limitation again causes abnormal load on the plantar surface of the foot, callus formation and an incorrect operation of the muscle pump. However, some of the forms of offloading, such as TCC, may be an obstacle to performing exercises [35]. The necessity of conducting research on an offloading device that does not hinder the involvement of the affected limb in simple exercises was emphasized by the authors of one of the last articles [74].

There is a lot of controversy when it comes to exercises during the active phase (open wound or inflammation) [16,75]. This is understandable considering the fact that most clinical trials are quite old, involve a relatively small number of patients and are not uniform in their design [40]. This makes them difficult to interpret in terms of patient benefits. Based on the available studies, the existing knowledge is sufficient to consider properly conducted rehabilitation as necessary even in the acute phase, with the principle of relieving the affected area of the foot and the absence of signs of general infection [76].Consistent with the above are the aforementioned recently published research results [36], which showed significant improvement in the healing of foot ulceration in patients with diabetes.

3.3. Impact of Exercises on the General Condition of a Patient with Diabetic Foot Disease

Immobilisation of the foot, unless there are general signs of inflammation, does not have to result in complete immobilisation of the patient in bed or a chair.

To perform a large part of daily activities, people involve the lower limbs. When this is limited by a disease, it should be considered whether lower limb muscle activity can be replaced with exercises that exclude the affected area of the foot or with work of the upper limbs or trunk. This is supported by the results of studies that emphasise the role of aerobic exercise in wound healing in animals [77,78,79,80] and humans [81], most likely through benefits for the respiratory and cardiovascular systems and improved glucose burning [35,82] resulting from tissue sensitisation to insulin. Strength training in preventing atrophy is also helpful in keeping the patient's muscles in better shape and building muscle mass, which translates into better glucose utilisation and improves muscle tone and coordination of movements [52]. Strengthening the muscles and the patient's general condition is of tremendous importance also if the treatment of the diabetic foot fails. If amputation and subsequent prosthetics are necessary, the patient's energy expenditure (EE) when moving is much higher than in able-bodied persons [83]. People whose condition indicates a high risk of amputation should be adequately prepared physically so that they can fully use the prosthesis in the future.

3.4. Benefits of Different Types of Exercises Performed by a Patient with Diabetic Foot Disease

Patients can exercise while sitting or lying down, depending on their overall health and the location of the ulcer. Ankle mobility exercises, such as plantar and dorsal flexion (including toes, separately), pronation and inversion or foot circles are safe and easy to perform, even for elderly people. Their role is to maintain or improve blood flow and joint mobility, they have an antithrombotic and anti-swelling effect. There are also no contraindications to performing simple exercises involving the larger joints of the lower limb (such as alternating flexion/extension at the knee or hip joint or the so-called bicycle exercise while lying on the back). In patients with heel ulcers, a prerequisite during such exercises is the ability to lift the heel during movement, e.g., when bending at the knee joint, so that the patient does not rub the affected area on the ground.

Patients with an ischemic foot may also (if they tolerate pain or take pain medication) raise their lower limb and perform the exercises in that position. This is an element of the Buerger [69,70,71] exercises recommended for leg ischemia.

In the absence of contraindications to loading (e.g. when the wound involves the dorsum of the foot) a standing or at least sitting position is recommended. Energy expenditure is approximately 10% higher in the standing position compared to when a person is sitting or lying [84], therefore the change in the patient's position should be considered beneficial, e.g. for the degree of glucose utilisation.

Exercises can also be performed with the involvement of the upper limbs. Strengthening the muscles of the rim and the free upper limb, apart from its overall impact on the patient's well-being, respiratory and circulatory systems, is useful due to the patient's potential need to move in a wheelchair or on crutches if the treatment fails and amputation is necessary [85]. The work of the arms seems to be as burdensome for the body as the work performed using the lower limbs [86], with even better synchronisation of breathing with the movements of the upper limbs (vs lower limbs) during submaximal exercises [87]. However, whenever possible, patients should be encouraged to perform dynamic exercises using both the upper and lower limbs (e.g. non-weight bearing combined arm + leg cycling), if only due to the accompanying higher energy expenditure and effect on aerobic conditioning, necessary with limited other types of activities [88].

Isometric exercises (alternate tensing and relaxing of muscle parts, without changing the distance of their attachments) are also a frequently used form of rehabilitation when one is unable to move or as a supplement to dynamic exercises. Due to the lack of need for additional movements, they can be performed by people with low physical fitness and poor physical condition, thus easily improving muscle strength and blood flow. Tensing muscles should be avoided in the area where sutures are placed (e.g., to bring the edges of a wound closer or minor amputation) or in the area of fractures (Charcot's foot) so as not to cause the bones to shift relative to each other due to the tensing of the muscles. The undoubted advantage of the exercises is that they can also be performed in situations of permanent immobilisation, with dressings often used for the purpose of offloading.

Learning to walk using crutches remains an element of rehabilitation, both in terms of utility (a way to move around without burdening the affected foot) and EE. Walking on crutches on flat ground or up the stairs is an effort of about 4.5 and 5.0 metabolic equivalent (MET), respectively [89]. Therefore, patients should not be persuaded to use electric wheelchairs for no reason, especially to cover short distances.

Calisthenics strengthens muscles and leads to an additional EE and good heart rate (HR) response [90]. Simple muscle-strengthening exercises like bedside squats (only when the wound is on the upper part of the foot) [91], sit-ups or other forms of muscle strengthening using simple instruments, e.g. stretching rubber bands, squeezing rubber balls, upper limb exercises with weights, are useful in working with patients. Their role often seems small and is underestimated but, e.g., the intensity of chair-assisted exercises could be at least moderate and these exercises can give about 61% of VO2max, 67% HRmax and about 3.9 METs loading [91].

In addition to the above-mentioned exercises, patients with foot deformity without ulceration can perform low-intensity aerobic exercises in standing or walking position after fitting an orthotic, if necessary, or with the use of made-to-measure shoes or individual orthotics. If such exercises are performed on a bicycle, the orthosis must be adapted to the foot deformity and the need to redistribute the pressure of the sole on the pedals should also be taken into account [52] . A good exercise environment for people with deformities without ulceration is water [52].

Table 1 presents examples of simple exercises that can be performed by patients with diabetic foot disease.

Analysing recent reports, it is worth mentioning the possibilities offered by virtual therapy. The impact of some forms of virtual training on aerobic capacity, functional lower-limb strength, reaction time and pain reduction have been documented [92]. This new and still experimental form of rehabilitation takes advantage of the well-known physiological phenomenon of activating the neural networks of the cerebral cortex and cerebral subcortex, which contain the so-called mirror neurons. After watching an exercise being performed (the element of virtual therapy), its performance is simpler and more correct due to the enhancing adaptive neuroplasticity mechanisms [93]. Although there are no studies for patients with limited mobility due to the diabetic foot, various research using mirror neuron-based therapy have proved its effectiveness on several motor functions in populations with neurological diseases [94,95,96,97] and it seems reasonable to preliminarily extrapolate the obtained results also to patients with DM and foot problems until that population is studied. The introduction of virtual reality-based therapy can be an additional tool in the effective use of rehabilitation time in the aforementioned group of people, without the risk of tissue damage or other side-effect.

4. Conclusions

In the absence of data on the harmful effects of properly performed exercises in patients with diabetic foot disease and taking into account the documented benefits of exercises on the general condition of the patient, and in some cases the local condition, it should be recommended that their performance should be part of the DFD therapy. Exercises can be dynamic, aerobic or anaerobic and may include isometric exercises or other: calisthenics, stretching and joint mobility improving exercises. Their choice depends on the location and nature of the foot change, the need for and offloading type, the presence of pain and the patient's condition. One should remember not only to exercise the affected limb but also, and often especially, other parts of the body. If possible, virtual therapy should be considered. Staff emphasising the advisability of incorporating exercises into the therapy plan and their safety is probably one of the most important factors determining the patient's involvement. The exercise plan should be prepared at the beginning of treatment and modified according to changes in the patient's general condition and local changes, as well as the implemented therapies and their effect.