Geriatric rehabilitation has evolved in recent years due to the increased life expectancy and the increased relative proportion of elderly and old people in the population, including in the European Union and in our country. We present the basic principles of geriatric rehabilitation, emphasizing its specificity in the elderly and old people. We present our own algorithm for functional assessment and geriatric rehabilitation (kinesio- and ergotherapy, electro- and light therapy, cryo- and thermotherapy). Particular attention is paid to autonomy in everyday life. Some measures of physical prevention, therapy, and rehabilitation for the most common problems of patients in the clinical practice of geriatric rehabilitation are highlighted. We emphasize the rehabilitation of some “geriatric giants”: hypodynamia; impaired balance, posture, and gait with frequent falls; reduced memory capabilities; sarcopenia, frailty, and cachexia.
Activities of daily living; Autonomy; Exercise; Frailty; Geriatric rehabilitation; Physical activity; Physical medicine; Sarcopenia
“Old Age: the crown of Life, our play's last act.” Marcus Tullius Cicero
“Caregiving for an elderly parent is an ongoing learning experience.” Unknown
Ultimately, we observe a rise in the average lifetime [1], respectively an expansion of the part of old people in the total population structure [2]; which determines the increased interest in the problems of these types of patients. According to the United Nations prognosis [3], the number of people, aged 60 and over, will double by 2050 and triple by 2100. The population of the over-60s is growing at a faster rate than that of younger age groups [4,5]. According to EUROSTAT, an increased life expectancy is detected [6]. Life expectancy per newborn child in the European Union is around 81 years (2016 data); with the highest data for Spain (83.5 years) and Italy (83.4 years); and the lowest for Bulgaria, Latvia, and Lithuania (around 74.9 years). We do not yet have the final version of these data and projections following the COVID-19 pandemic, which was characterized by relatively higher mortality among the elderly and old people.
It is well known that in medical practice, the major clinical disciplines decide the patient's prognosis quo ad vitae, but physical factors ensure his quality of life. Physical medicine stands on the solid foundation of medical sciences. According to the European Definition of the Medical Act [7]: “The medical act includes all professional activities, including science, teaching, specialisation and training, clinical and medico-technical steps; aimed at health promotion, disease prevention, provision of diagnosis and of curative care to patients, individuals, groups and communities. It is the responsibility of, and must be exercised at all times by, a registered MD/Physician - in person or under his/her direct supervision and/or prescription.”
In the context of this definition, physical factors are primarily aimed at health promotion, disease prevention and curative recovery of patients and persons with disabilities. Physical methods and means are able to provide a better quality of life, both for the healthy and the sick person. Physical and Rehabilitation Medicine (PRM), as defined by the PRM Section of the European Union of Medical Specialists [Union Europeenne des Medecins Specialistes (UEMS) - PRM Section], is “an independent medical specialty focused on the promotion of physical and cognitive functioning, activities (including environment), participation (including quality of life), and modification of personal and environmental factors. PRM is responsible for the management of the prevention, diagnosis, treatment, and rehabilitation of people with health-related disabilities and comorbidities of all ages. “ [8-10].
The regulations of the Bulgarian School of Physical and Rehabilitation Medicine (including the Medical Standard on PRM [11] have been harmonized with those of the European Union and the European Union of Medical Specialists - PRM Section. According to the World Health Organization (WHO), Rehabilitation is “the use of all means aimed at reducing the degree of incapacity and disability, and at training people with permanent incapacity to obtain optimal social integration”. Rehabilitation is a set of medical, social, educational, and vocational activities carried out jointly and in a coordinated manner in the case of persons with reduced working capacity due to illness or other impairments, with a view to achieving the maximum possible physical, mental and working capacity. Its main sections are medical-psychological, occupational, and socio-legal rehabilitation.
According to the World Report on Disability of the WHO and the World Bank [12] the goals of rehabilitation include prevention of the loss of function; slowing the process of loss of function; improvement or restoration of function; compensation for lost function; and maintenance of current function. According to actual understanding [13], rehabilitation is a functional therapy, based on a detailed functional assessment. Contemporary Physical Medicine [9,10,11,13] uses a combination of methods for functional evaluation and physical therapy, as well as multiple physical factors (PF):
In geriatric rehabilitation, ultimately we emphasize kinesiotherapy and occupational therapy, using also some treatments with preformed factors, especially functional electrostimulation (in case of motor deficits), Transcutaneous Electroneurostimulation (TENS) and magnetotherapy (for pain relief); laser therapy (in case of autonomic dysfunction).
Ergotherapy (ET) has recently started to develop in our country [14]. Etymologically, the term ET originates from the Greek words: ergon - work and therapeia - therapy, i.e., treatment with work or activities. According to medical definitions [15], ET represents the application of various activities for the treatment of diseases. According to modern conceptions [16], ET applies targeted, problem-oriented activities to improve the quality of life of people with disabilities. It is based on the following postulate: Purposeful activity can be used for the prevention of physical or psychosocial dysfunction and also for functional recovery. ET includes three main elements, namely: training the disabled person to cope alone in the environment; adaptation of the environment to the needs of the disabled person; and assistive devices (splints, belts, crutches, canes, canes; wheelchairs, etc.,). In many countries, occupational therapy is a separate profession [17,18]. In the rehabilitation of the elderly and the aged, we emphasize ET areas related to self-care activities, recreation, and rest.
Gerontology and Geriatrics investigate the medical aspects of aging - in norm (healthy aging) and pathology. Gerontology studies the factors leading to aging, or the mechanisms of the aging process. Geriatric medicine treats diseases in elderly patients. The terms derive from Greek: γερων (geron) -- “elderly person” ιατρóς (iatros) -- “healer”, λογοσ logos (logos) -- science. According to the World Health Organisation’s motto, the aim is: “to add life to years, not just years to life”; i.e., to improve the quality of life of the elderly and old people. Geriatrics is considered an interdisciplinary scientific field that deals with problems mainly in the fields of internal medicine, orthopedics, neurology and psychiatry (gerontopsychiatry). It focuses on the biology of aging [19,20]: decline in biological functions; polymorbidity; slow reconvalescence; delayed tissue regeneration (including wounds); multiple complications.
Dr. Leo Nascher of Mount Sinai Hospital in New York is considered the “father” of geriatrics in the United States. As “mother” of geriatrics in Europe is considered Dr. Marjorie Warren, a physician from London who was the first to emphasize the need for a holistic approach and for rehabilitation in the elderly [18]. After her, other physicians and authors emphasized polymorbidity, the holistic approach, and the role of rehabilitation in this contingent of patients [21,22].
The British physician Dr. Bernard Isaacs emphasized on the specifics of the clinical picture in the elderly. He formulated the rule of the four letters I: Immobility, Instability, Incontinence, Intellectual Impairment (Impaired intellect) [23]. To these ‘geriatric giants’, described by Professor Isaacs, a fifth has been added recently: Impaired vision and hearing loss. All these ‘geriatric giants’ can be observed in most elderly and aged people, leading to difficulties in treating their illnesses and impairments, as well as more serious complications and deterioration in their quality of life [24-28]: weight loss, muscle weakness, reduced physical activity, delayed ambulation; social isolation, depression; frequent falls; medication errors; and incorrect financial management. Consequences are complex: Limited autonomy in daily life; Restrictions in activities; Restraints in participation; Impaired quality of life; Dependence on others' help; Social isolation; Need for social assistance at home or from specialized facilities - rehabilitation hospitals, hospices, etc., i.e., two contradictory laws are valid in these patients: the razor of Ockham (the role of age - Lex parsimoniae: Entia non sunt multiplicanda sine necessitate; Wilhelm of Ockham), but also the rule of Hickam (Hickam’s dictum-polymorbidity).
In the area of gerontology and geriatrics, we observe several thematic fields, sub-fields and sub-specialties, namely:
Geriatric rehabilitation comprises a detailed functional assessment and complex functional therapy. The development of Geriatric rehabilitation began towards the end of the last century, with the Mayo Clinic in the USA considered to be the most advanced in the field [29]. The main goal of geronto-rehabilitation is to support the functioning of the elderly and old people despite their physical and mental disabilities [30]. The rehabilitation is performed by a team consisting of medical specialists (gerontologist, cardiologist, orthopedist, rheumatologist, PRM), medical specialists (nurse, rehabilitation specialist) and non-medical specialists (kinesiotherapist, occupational therapist, social worker, etc.,). In the majority of cases, the final goal is obtained - amelioration even restoration of the quality of life of geriatric patients.
Its basic principles are prevention of disability and therapy, restoration and preservation of function as much as possible, and adaptation to lost function (due to aging) [29,30]. All authors stress the extreme importance of functional training (of movements, activities, cognition), according to the principle “Train the function or you will lose it” (“Use it or Lose it”) [31].
For rehabilitation clinical practice, the most important signs of normal aging are [32]:
Basic objectives and tasks of gerontorehabilitation include:
The three main areas of geriatric rehabilitation are: ‘normal’ (‘healthy’) aging, cardiovascular problems (heart failure and stroke), and skeletal problems (osteoporosis, osteoarthritis, and polyarthritis; hip and knee arthroplasty).
Indications for gerontorehabilitation include:
There are a number of dysfunctions and deficits in diseases of the nervous system and musculoskeletal system. The most common include somatosensory and motor deficits, disorders of postural adaptation and motor planning; balance and coordination disturbances; cognitive dysfunctions; emotional lability; limited autonomy in activities of daily living.
Rehabilitation clinical practice requires precise diagnostics - according to the International Classification of Diseases [33] and the International Classification of Functioning, Disability and Health [34]. In order to analyze the patient’s condition in detail, multiple clinical, paraclinical, and instrumental methods are applied, both standard for each type of rehabilitation [35-38] and specific for gerontorehabilitation [39]. Especially important are the investigations applied to diseases and injuries of the nervous system [40,41] and of the musculoskeletal system [42].
Include Somatic exam; Neurological exam - with an evaluation of the motor function (weakness, paresis, paralysis); ataxia; radicular signs; Orthopedic exam with assessment of the range of motion, joint stability, and functional tests; Rheumatologic exam with tests of Ott, Schober, Patrick, Bonnet; Evaluation of the functional grasp and grip (0-5); Balance and Gait assessment with a prognosis of risk of falls; Kinesiological analysis, including Manual muscle test (MMT - Lovett, 0-5); Evaluation of autonomy in Activities of Daily Life (ADL) and need of assistance; Assessment of the quality of life (WHODAS 2.0. - 12 and 36 points; Psychological exam.
Blood exam, evaluation of glycemia, lipid parameters; emphasizing on Hb, Leuco, CRP; in men - PSA.
Electrocardiography and Echocardiography; Neuro-imagery (X-Rays, Computer tomography, Magnetic resonance imagery); Neurofunctional methods (Electroneurography, Electromyography, Excitomotoryelectrodiagnostics, Doppler-sonography, Laser-Doppler-flowmetry).
During the investigation of the rehabilitation potential of a patient, the holistic approach should be mandatory, i.e. the performance of a comprehensive assessment of cognitive ability (orientation, attention, memory, ability to collaborate in the implementation of treatment interventions; awareness of the precautions to be observed in relation to the underlying neurological suffering); pain (localization, type, severity /verbal or visual-analog scale/; activities that lead to increased pain);range of motion (active and passive); muscle strength (weakness), presence of motor deficit; coordination (static, locomotor and dynamic ataxia); mobility (need for aids, appliances, tools, and devices); endurance (exercise tolerance, need for breaks during the examination and functional activity); testing of the autonomy in everyday life (bathing, dressing, feeding, personal hygiene; need for assistance with self-care).
Specific scales are applied for the general assessment of the geriatric patient and for the assessment of autonomy in Activities of Daily Living (ADL). We emphasize autonomy during everyday functional activities; the necessity of assistance and of technical aids; balance, gait, and falls; manipulative capacities with upper limbs; cognition. For the evaluation of autonomy in Activities in Daily Living (ADL), we apply the scale of Katz (for self-service) and the instrumental scale of Lawton.
If possible, the final complex assessment should be based on the ICF and includes:
The general strategies to influence the most common socially significant diseases (including in geriatric patients) comprise systemic drug treatment, periodic courses of rehabilitation, as well as mandatory hygienic and dietary measures to optimize lifestyle: strict control of certain blood parameters (lipid profile, glucose, rheological indices), balanced diet and weight control, active exercise regime (kinesitherapy), minimization of harmful habits [43,44]. Most authors emphasize the importance of movement: basic motor activity and specific exercises [45,46]. A multi-disciplinary multi-professional team is needed [32,47,48]. The treatment algorithm is based on the synergism between physical factors [49]. This is the concept of the rehabilitation puzzle - a synergic combination between different natural and preformed physical modalities and treatment methods. The group of natural factors includes physiotherapy (active and passive movement), ergotherapy (activities), aerotherapy (respiratory techniques, inhalations), balneotherapy (mineral baths, douches), balneo physiotherapy (underwater exercises, underwater massage), thalassotherapy (influence of the seawater and sea climate). The group of preformed physical modalities contains electrotherapy (low, middle, and high-frequency electric currents), magnetotherapy (low-intensity magnetic field), ultrasound therapy (ultrasound and phonophoresis), photo-therapy (infra-red and ultra-violet light beams, laser) [50,51].
In general, we recommend a combination of one or two procedures with preformed physical factors, one or two procedures of cryo-thermo-peloido-balneotherapy, and two or three physiotherapy and ergotherapy techniques. However, for adult patients, we prefer a combination of one treatment with preformed physical factors (electrical stimulation, deep oscillation, laser, magnetic field), one thermo-procedure (with paraffine, peloid, or sea lye), two physiotherapy procedures (exercises, post-isometric relaxation, stretching, massage), and certainly one occupational therapy procedure.
The most frequent complications among the geriatric population include specific complications and require specific rehabilitation approaches [52].
In older patients, we observe numerous musculoskeletal problems: osteoporosis, osteoarthrosis and arthritis [47,53]. Muscular changes include a reduction in myocytes, lipofuscin deposits in muscles, muscle hypotrophy, reduction of muscle force and muscle contractility, and muscle tone [53]. Bone changes include osteoporosis, osteopenia and reduction of the body height [53]. The ability of bones to tolerate mechanical stress is reduced. Over time, due to stress, micro-fissures develop in the bones. I.e., the quality of the bone decreases, leading to an increased risk of fracture. The quality of the bone is diminished and osteoporosis is developed, with microarchitectural changes, decreased bone mineral density, and increased risk of fragility fractures. Mobility decreases with age. Movements become more difficult, painful and ineffective. Between 40 and 70 we observe a loss of muscle strength of about 10-20%. Between 70 and 80 - the loss becomes 30- 40% [54]. Decreased physical activity or even immobility (a consequence of hospitalization) may provoke deconditioning with reduced strength and flexibility [55].
Muscles and bones need movement, active exercise, and sports. Classic recommendations comprise regular physical activity: walking, running, cycling – three or four times weekly. Physical activity is beneficial for both athletes and people who have a sedentary lifestyle. We recommend periodic osteodensitometry and consultation with a rheumatologist and/or endocrinologist. Clinicians also require laboratory monitoring of the following key parameters: ionized Calcium levels; 25-OH vitamin D, phosphorus, BUN, creatinine, albumin, total protein, Thyroid-Stimulating Hormone (TSH), and T3/T4, cortisol, alkaline phosphatase. In men: testosterone bioavailability. In women: estrogen levels; Liver function tests.
Apart from medication and standard phototherapy, specialists in Physical and Rehabilitation Medicine (PRM) recommend regular physical activity with active exercises, walking in the parc or in the mountain (cross-country route); thalassotherapy (swimming; underwater exercises). The main elements of the specialized PRM program include aerobic exercises; Low-intensity prolonged exercise: mechanotherapy; low-intensity aerobics; steppers; walking (treadmill); low-intensity sports and activities; High-intensity short or intermittent exercise and activities: walking, stair climbing, dancing, fast walking or running, jumping jacks, step aerobics, tennis, garden work. According to the prescription of the physician-PRM specialist we can include procedures with preformed physical modalities: magnetotherapy, interferential currents; transcutaneous electroneurostimulation.
The role of proprioception in balance and gait is well known [25,26]. It is an established fact that proprioception is impaired with aging [56], requiring systemic proprioceptive stimulation (primarily of the proprioceptors in the joints and tendons of the lower limbs). In geriatric rehabilitation clinical practice, we investigate proprioception by assessing the joint position and the sensation of movement of the lower limbs, at the hip [57], knee [58,59], and ankle joints. The effects of regular motor activity [57,60] as well as some low-intensity whole-body movements, such as Tai Chi [61], were objectified. Targeted proprioceptive stimulation [62] is performed with analytical exercises, vibratory massage and proprioceptive neuromuscular facilitation (PNF techniques). In turn, improved proprioception leads to stabilization of balance [21] and reduces the risk of falls and fractures, respectively, in the elderly and old people.
Falls - Risk Factors [19]: Often falls are observed in older white women with low Body Mass Index (BMI), greater height, lower Bone Mineral Density (BMD), and a history of cerebrovascular accident in the vertebrobasilar system (vertebrobasilar insufficiency). Alcohol consumption-related falls are more common in men. A surprising fact: 14% of adult patients in the urgency are alcohol-dependent. Women more often fall on the glutes (with femoral neck fracture). Craniocerebral injuries are more common in men.
Authors mention some intrinsic factors predisposing to falls in the elderly and aged [19]: history of previous falls, possibly fractures; impaired proprioception; gait characteristics: slow gait; variability between different walking cycles increases the likelihood of falling by about 5 times (uneven gait - stride-to-stride variability); particularities in the end push-off phase; the presence of multiple risk factors. Old patients usually present some gait peculiarities [21]. They have a slow gait; with variability between different walking cycles; and end-phase push-off peculiarities. Patients who fall forward usually have increased hip flexion and decreased knee flexion in the pre-swing phase, and decreased knee stability in the pre-swing phase.
Age-related risk factors for falls include [24,26]:
Strategies for the reduction of the risk factors include [29]:
Mandatory elements of the geronto-rehabilitation complex are Regular physical activity (in nature), Hiking; Training of proprioception; Balance exercises; Coordination Exercises; Gait training /with aids, if necessary); Training in activities of daily living; Assessment of fall risk and precautions to reduce it.
Ergotherapy (ET) or Occupational Therapy (OT) is the most adequate method for the amelioration of the autonomy of geriatric patients in daily life. It includes both patient education and training for self-care activities; the use of assistive devices, also home adaptation. We cite the main stages in Activities in Daily Living (ADL) for an increase of patient mobility in the clinical practice of geriatric rehabilitation (especially in cases with conditions and diseases of the nervous system and the locomotory system): Turning in bed; Long sitting; Sitting in bed with legs lowered; Verticalization; Balance training; ADL training; Gait training - flat; then climbing stairs up, then down.
We propose to our patients some examples of home adaptations tailored to individual needs:
Examples of assistive devices that could improve the independence of geriatric patients are canes, crutches, walkers, and wheelchairs. Some orthotic devices are also recommended to maintain body posture: thoracic belts, lumbostats, elastic stockings, etc.
Both degenerative and vascular dementias are common. Differential diagnosis with delirium and agitated depression is important.
In rehabilitation clinical practice, ergotherapy is recommended to train both the right and left cerebral hemispheres - i.e., engaging in a variety of logical thinking activities as well as artistic and orientation activities. To train the dominant hemisphere, we apply various puzzles, logic tasks and tests are applied. To train the nondominant hemisphere, different variants of art therapy are recommended.
Art therapy is a specific form of therapeutic influence. The root of the term “art therapy” is of Latin origin: “art” means art, and “therapia” - treatment, healing, medical care, i.e., treatment with or through art. Art therapy was originally created as a healing tool applied to psychiatric patients. Gradually it became more and more extended to other clients (patients, but also healthy persons). According to the Association of British Art Therapists, art therapy is “the use of artistic means for self-expression and self-awareness in the presence of a trained art therapist”. Clients, who are referred to an art therapist, do not need previous experience or skills in the arts; the art therapist does not seek to make an aesthetic or diagnostic assessment of the images created by the client. The practitioner's primary goal is to help the client achieve personal change and development through the use of art materials in a safe and supportive environment. Art therapy is used for functional disorders of the nervous system in adults with mental problems - depressive or aggressive behavior, irritability, fears, etc. It has both distracting and training effects on the elderly - healthy and ill patients. In art-therapeutic work, there is a synchronization and linking of the activities of different specialists - educators, psychotherapists, psychologists, doctors, social workers, rehabilitators, etc.
The term Sarcopenia was proposed by Rosenberg for the age-related reduction of muscle mass. It comes from the Greek words ‘sarx’ (flesh) and ‘penia’ (loss). Sarcopenia is characterized by a progressive and generalized loss of skeletal muscle mass and strength; resulting in physical dysfunction, impaired quality of life, and ultimately death [63-65]. The loss of muscle mass impairs strength, immunocompetence and metabolic homeostasis of the body [66]. Reduction of muscle mass leads to functional impairment, frequent falls and loss of autonomy in activities of daily living [67]. Several consensus definitions of sarcopenia have been published [68]. The measured parameters are walking speed, grip strength and muscle mass. Several authors consider that the development of sarcopenia is a continuing process. Some introduce the term Skeletal muscle function deficit [69], others - Presarcopenia [70]. The European Working Group on Sarcopenia in Older People proposed three conceptual stages of sarcopenia: Presarcopenia, Sarcopenia, and Severe sarcopenia [70].
In some conditions (malignancy, rheumatoid arthritis), we can observe sarcopenic obesity with decreased body mass, but preserved or even increased fat mass [71].
The “gold standard” in the treatment of sarcopenia is physical training with resistance-type exercises with progressive load [72,73]. A specific diet with high protein intake is considered synergistic [74]. According to some studies, resistance exercise is always useful, without non-responders [75].
Frailty is an age-dependent condition [76], including a decrease in reserves and increased vulnerability [77]. This multi-dimensional loss of reserves comprises declines in energy production and utilization, resulting in functional insufficiency and altered stress response [78]. Linda Fried from the Johns Hopkins University’s Center on Aging and Health defines a frailty phenotype (physical frailty) with a minimum of three of five criteria: weakness, slowness, low physical activity, exhaustion (or fatigue), and unintentional weight loss [78]. A concept of “Cascade of functional decline of older adults” is described, with several stages: Robustness, Pre-frailty, Frailty, and Disability, demanding assistance in ADL [79].
A total of 36 experts from different countries (Australia, Europe, USA, Canada, Asia) - members of the task force of the International Conference of Frailty and Sarcopenia Research (ICFSR) published in 2019 Guidelines for Identification and Management of physical frailty [79]. The prescription of physical activity is included as a strong recommendation with moderate certainty of evidence. We can cite: “Recommendation No 5: Older people with frailty should be offered a multi-component physical activity program (or those with pre-frailty as a preventative component).”
The term “Cachexia” derives from the Greek: ‘cac’ (bad) and ‘hexis’ (condition). Cachexia is defined as a loss of muscle mass (eventually muscle and fat mass), due to an underlying illness (cancer, congestive cardiomyopathy, or end-stage renal insufficiency) [80]. Every type of physical activity can be useful.
Physical inactivity and a sedentary style of life are typical for older adults. So, regular physical activity is recommended by many authors. The beneficial effects are numerous [81]: reduction of risks of chronic diseases and all-cause mortality; preservation of functional capacity and improvement of the quality of life; a decrease in the effects of aging; lessening oncologic risks, risks of overweight and obesity, and risks of falls; reduction of anxiety and depression.
The U.S. National Institute on Aging recommends four types of exercise to improve health and fitness:
An interdisciplinary approach is necessary for the assessment and management of aging [82,83]. According to our national consensus on geriatric rehabilitation: the necessary staff includes some permanent members of the rehabilitation team: attending physician - PRM specialist; physiotherapist, occupational therapist; patient and family. If necessary and according to the needs of the patient's main disease, the team also can contain other doctors (general practitioners and specialists - cardiologist, neurologist, orthopaedist-traumatologist, obstetrician-gynecologist; radiologist and radiologist, functionalists); nurse; midwife; kinesiotherapist; sociologist; speech therapist; clinical psychologist, psychotherapist, massage therapist, representative of a religious or patient organisation, etc.
Physical and Rehabilitation Medicine is very useful in the clinical practice of gerontology and geriatry. Our opinion is the future development of this interdisciplinary field has enormous potential. Properly structured and conducted PRM program ameliorate various clinical signs, symptoms and syndromes - it reduces pain (physical analgesia), increases the range of motion of the spine and limbs, supports the independence of the disabled in the activities of daily living, improves the quality of life of every old patient.
Citation: Koleva IB, Yoshinov BR, Yoshinov RR (2023) Impact of Rehabilitation Medicine in Gerontology and Geriatrics: Basic Principles. J Gerontol Geriatr Med 9: 178.
Copyright: © 2023 Koleva IB, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.