The Effect of Intradialytic Exercise on Postural Abnormalities

Falls represent one of the most consequential complications in patients with end-stage renal disease (ESRD), with approximately 25% of dialysis patients experiencing at least one fall annually. Fall-related injuries in this population, including hip fractures, vertebral fractures, and joint dislocations, contribute to significant functional deterioration, diminished quality of life, restricted mobility, and increased healthcare expenditure. Among the many factors driving this fall burden, postural abnormalities have emerged as clinically significant yet persistently underinvestigated contributors. In particular, thoracic hyperkyphosis and forward head posture (FHP) are now recognized as highly prevalent structural deformities in dialysis patients that directly impair postural stability, physical function, and overall safety.

The clinical impact of thoracic hyperkyphosis and FHP extends across multiple physiological domains. Hyperkyphosis, characterized by excessive posterior curvature of the thoracic spine, displaces the body's center of gravity anteriorly, impairing postural control and forcing compensatory adaptations in the lumbar spine and hips. When these compensatory mechanisms are overwhelmed, as is common in the context of the sarcopenia and muscle weakness that accompany ESRD, hyperkyphosis leads to impaired gait, reduced walking speed, diminished balance, and substantially heightened fall susceptibility. Beyond its musculoskeletal effects, thoracic hyperkyphosis restricts thoracic cage mobility, reduces vital capacity, and compromises cardiopulmonary function.

FHP, defined as anterior displacement of the head relative to the shoulder plumb line in the sagittal plane, generates disproportionate loading of the posterior cervical musculature and disrupts the normal biomechanics of the cervical spine. This misalignment reduces both static and dynamic balance by destabilizing the vestibular and proprioceptive feedback systems that depend on neutral cervical alignment. FHP has been associated with increased postural sway and instability in older adults, as well as altered thoracic shape and impaired respiratory function through weakening of the accessory breathing musculature. Critically, hyperkyphosis and FHP are biomechanically coupled: as thoracic kyphosis increases, compensatory anterior head translation increases proportionally to maintain horizontal gaze, creating a self-reinforcing cycle of progressive postural dysfunction and functional decline.

Despite the scale and clinical consequences of this problem, effective corrective strategies for dialysis patients remain largely untested. Evidence from general and older adult populations, however, strongly supports the role of targeted exercise in correcting both hyperkyphosis and FHP. Combined strengthening and stretching exercise programs, specifically targeting the thoracic extensors, scapular stabilizers, and deep cervical flexors while stretching the shortened anterior chain muscles, are found to produce significant reductions in kyphosis angle and improvements in craniovertebral angle across populations with postural deformities. These findings indicate that exercise-based postural correction is not only feasible but reliably effective in older adults with comparable musculoskeletal profiles to dialysis patients, making translation to the ESRD population a logical and clinically justified step.

The key challenge lies in delivering such exercise to a population with significant barriers to participation in community or home-based programs, including transportation dependence, fatigue, and medically complex comorbidities. Intradialytic exercise (IDE), supervised physical activity performed during scheduled hemodialysis sessions, offers a uniquely practical solution. By embedding exercise within the unavoidable treatment time of dialysis, IDE eliminates the need for additional healthcare visits, ensures direct professional supervision, and capitalizes on the structure of the dialysis schedule to provide consistent physical stimulation.

Despite this accumulating evidence, no published trial has specifically examined the effect of intradialytic exercise on the structural postural abnormalities of thoracic hyperkyphosis and FHP in hemodialysis patients. The present randomized controlled trial therefore aims to determine whether a 12-week supervised, multimodal intradialytic exercise program can improve spinal and cervical postural alignment, dynamic balance, physical function, and health-related quality of life in hemodialysis patients, providing the evidence needed to justify integrating postural correction into standard dialysis care.

Inclusion criteria

• Age 18-80 years
• Diagnosed with ESRD and receiving stable maintenance hemodialysis for at least 3 months at the participating center, with a dialysis frequency of three sessions per week
• Confirmed presence of at least one postural abnormality (hyperkyphosis ≥53° in women or ≥55° in men, or CVA <53°) assessed at screening
• Written informed consent obtained, indicating decision-making capacity and willingness to participate
• Medical clearance from attending nephrologist to participate in supervised exercise during dialysis
• Ability to sit upright in a dialysis chair and perform seated or supported standing exercises
• Ability to communicate in Persian and understand study instructions

Exclusion criteria

• Unstable cardiovascular status, including recent (within 3 months) myocardial infarction, unstable angina, decompensated congestive heart failure (NYHA Class III-IV), or uncontrolled arrhythmia
• Active infection, acute febrile illness, or acute medical condition requiring hospitalization
• Hemodynamic instability defined as systolic blood pressure <90 mmHg or >200 mmHg, or severe orthostatic hypotension, at screening or prior to exercise sessions
• Uncontrolled diabetes mellitus with labile glycemic control (blood glucose <4 mmol/L or >22 mmol/L at dialysis session start)
• Severe musculoskeletal pain at rest or with minimal activity (Numeric Pain Rating Scale ≥7/10) that would preclude exercise participation
• Inability to perform seated exercises, walk independently, or maintain upright posture; severe neurological disability
• Recent fracture (within 6 months) of vertebral column, pelvis, or lower extremities
• Severe peripheral neuropathy or vascular disease (ABI <0.6) precluding lower limb exercise
• Dyspnea at rest or with activities of daily living corresponding to NYHA Class IV
• Participation in a structured exercise program targeting postural correction, resistance, or balance training ≥3 times per week in the preceding 3 months
• Severe cognitive impairment (MMSE <18) preventing informed consent or adherence to exercise instruction
• Pregnancy or planned pregnancy during the study period
• Life expectancy <6 months as determined by the attending nephrologist
• Scheduled kidney transplantation within the study period