Feasibility of short-term supine rehabilitation for pediatric orthostatic intolerance: a case series

Abstract

[Purpose] This pilot feasibility case series examined the safety, tolerability, and implementability of a short-term inpatient supine exercise program using a low-load bicycle ergometer in pediatric patients with orthostatic intolerance (OI). [Participants and Methods] Four adolescents with OI who had difficulty attending school participated in a 10–13-day inpatient rehabilitation program. The intervention consisted of daily supine ergometer exercise (5-min warm-up, 15-min active pedaling, 5-min cool-down). Feasibility outcomes included completion rate, adherence, and adverse events. Exploratory clinical outcomes included heart rate (HR) response during standing tests, perceived exertion using a 100-mm visual analog scale (VAS), and school attendance two weeks after discharge. [Results] All participants completed the program without adverse events, demonstrating good feasibility and safety. Adherence to supervised sessions was high, and all patients performed self-training. Improvements in perceived exertion were observed in all cases, whereas changes in HR responses were variable. School attendance improved in three patients, although only two were able to attend more than three days per week. [Conclusion] A short-term supine ergometer program appears feasible, safe, and well tolerated in pediatric patients with OI. Given the small sample size, lack of controls, and reliance on subjective outcomes, these findings should be interpreted cautiously.

INTRODUCTION

Orthostatic intolerance (OI) is characterized by symptoms triggered by standing and relieved by recumbency¹⁾. Causes include orthostatic hypotension (OH), initial OH, delayed OH, postural orthostatic tachycardia syndrome (POTS), and neurally mediated syncope (NMS)^2,3,4). Non-pharmacological management is the first-line treatment and includes exercise therapy^{2, 5, 6)}. The main pathology of exercise were suggested to reduce venous return, which can improve with exercise. Supine incline training has been shown to enhance circulatory responses and baroreflex function in children with OI^{7, 8)}. Exercise increases cardiac output, systemic circulation, and autonomic regulation, thereby preventing hypotension and cerebral hypoperfusion^{9, 10)}. Strengthening lower-limb muscles aids venous return, whereas endurance training expands blood volume and stabilizes blood pressure¹⁰⁾. Short-term training (approximately three months) increases oxygen uptake, heart size, myocardial mass, and blood volume^11,12,13). These cardiovascular benefits are notable in youth and may be more pronounced in older patients^14,15,16,17).

Recent studies have reported the effectiveness of recumbent exercise in adolescents with postural orthostatic tachycardia syndrome (POTS)¹⁴⁾. Therefore, this study aimed to investigate the feasibility, safety, and implementability of a short-term supine exercise program in pediatric patients with OI. We hypothesized that the intervention would be feasible and well tolerated in this population.

PARTICIPANTS AND METHODS

This pilot case series involved a short-term inpatient rehabilitation program. Exercise was performed using a portable pedal-type bicycle ergometer suitable for bedside use in the supine position. Resistance was manually adjustable, and exercise was performed actively without motor assistance. The ergometer used in this study was a commercially available portable pedal-type device that could be used in the supine position at the bedside. The device allowed manual adjustment of resistance levels. Exercise was performed actively by the patients without motor assistance. Patients exercised in a supine position with the hip and knee joints slightly flexed, and the device was positioned to allow comfortable pedaling. Cadence was maintained at approximately 40–60 revolutions per minute. Exercise intensity was determined based on perceived exertion using a visual analog scale and corresponded to a moderate level of effort. Heart rate and subjective symptoms (e.g., dizziness, fatigue) were monitored during sessions, and exercise was discontinued if symptoms worsened.

Exercise was performed using a portable pedal-type bicycle ergometer designed for bedside use in the supine position. The device used in this study was the SDG Terasu Ergo 4 (SDG Co., Japan), a low-load adjustable ergometer with a resistance range of 3–20 W, suitable for pediatric patients with orthostatic intolerance. Exercise was performed actively by the patients without motor assistance. Patients exercised in the supine position with slight hip and knee flexion, and the ergometer was positioned to allow comfortable pedaling without elevating the trunk. Pedaling cadence was adjusted to achieve a perceived exertion of 6–7 on a 10-point scale, corresponding to approximately 40–60 revolutions per minute. Heart rate and subjective symptoms (e.g., dizziness, fatigue) were monitored continuously, and exercise was discontinued if symptoms worsened. Each session consisted of a 5-min warm-up, 15-min active pedaling, and a 5-min cool-down. Consecutive patients with orthostatic intolerance (OI) who regularly visited the Department of Pediatrics Medicine at Nara Prefectural General Medical Center (Nara, Japan) between January 2023 and March 2024 were enrolled. Eight patients were screened, and four patients and their families provided consent and were included in this study (Table 1). The inclusion criteria for patients were as follows: patients younger than 18 years who had experienced chronic orthostatic symptoms for at least three months, such as dizziness, morning fatigue, or difficulty standing, which interfered with school attendance or daily activities. The diagnosis of orthostatic intolerance was confirmed using the head-up tilt test (HUT). Eligible physiological responses included postural tachycardia syndrome (POTS), defined as an increase in heart rate of ≥40 beats/min within 10 min of standing or tilt in children aged 12–19 years, or ≥30 beats/min in children younger than 12 years, without orthostatic hypotension. Patients with orthostatic hypotension (initial or delayed), characterized by a transient or sustained decrease in blood pressure accompanied by orthostatic symptoms, were also included. All patients had shown insufficient improvement despite lifestyle recommendations such as increased fluid and salt intake. The absence of neuromuscular disease was confirmed by both a neurologist and a pediatrician. Written informed consent was obtained from all patients and their families.

Table 1. Demographic and clinical characteristics of the patients.

Patient	Age (years)	Sex	Height (cm)	Weight (kg)	Medical history	Comorbidities	Total GMT	Lower limb GMT	FIM	Diagnosis	School attendance before admission
1	11	Male	150	30	Delayed development	Asthma	4	4	113	POTS	Unable to attend
2	14	Female	152	45	None	None	4	5	119	POTS	Unable to attend
3	13	Male	159	52	None	None	4	4	106	POTS	Partial attendance
4	13	Female	153	41	Suspected selective mutism and autism spectrum disorder	None	4	4	124	POTS	Unable to attend

Patient 1 (P1), Patient 2 (P2), Patient 3 (P3), Patient 4 (P4). GMT: gross muscle test; FIM: functional independence measure; POTS: postural orthostatic tachycardia syndrome.

Patients were excluded if they had used unapproved medications for OI within the 12 months prior to enrollment, had a history of surgery that could affect autonomic or cardiovascular function, were unable to complete questionnaires or participate in assessments, or were considered unsuitable for participation by the principal investigator or co-investigator. Due to the small sample size of this preliminary study, statistical analysis was not performed.

This pilot study involved hospitalization for two weeks and a 10-day rehabilitation program. The rehabilitation program consisted of exercises performed in the supine position using a bicycle ergometer (5-min warm-up, 15-min exercise, and 5-min cool-down) (Fig. 1a). Exercise therapy was tailored to each patient’s exercise tolerance. Exercise intensity was set at approximately 70% of the patient’s subjective tolerance, based on a previous clinical trial in young adults¹⁸⁾. In adults, this corresponds to approximately 70% of the maximum heart rate. However, because the maximum heart rate in children varies widely, subjective tolerance was assessed using the visual analog scale (VAS). The exercises were performed under the supervision of a physiotherapist. In the afternoon, an ergometer was provided at the patient’s bedside, and patients were instructed to perform self-training. Additionally, lifestyle guidance was provided to the patients by nurses (Fig. 1b).

Fig. 1.

Rehabilitation protocol. (a) Rehabilitation program. (b) Daily schedule.

Evaluations were conducted in the morning before rehabilitation. Independent physiotherapists who were blinded to the protocol assessed the patients. We measured fatigue upon waking using the VAS, which was assessed using a 100-mm scale. We performed three main assessments: heart rate (HR) changes during active standing (AS), tilt table standing (ST), and the VAS score. Vital signs were recorded before, during, and after intervention, and circulatory dynamics were evaluated using the head-up tilt test (HUT) (FINAPRES NOVA): 7 min supine rest, 3 min AS, 7 min rest, and 7 min ST. Feasibility outcomes included completion rate, adherence, and adverse events. Clinical outcomes included HR response during active standing and tilt testing, VAS scores, and school attendance after discharge. Muscle strength was measured with the Gross Muscle Test (GMT) for upper-limb shoulder flexion and average hip and knee flexion–extension scores. Activities of daily living (ADL) were assessed using the Functional Independence Measure (FIM). Compliance with exercise therapy was monitored daily. Two weeks post-discharge, an outpatient consultation was conducted to evaluate school attendance, exercise habits, and fatigue.

This study was approved by the Ethics Committee of the Nara Prefectural General Medical Center. All study procedures were conducted in accordance with the Declaration of Helsinki and Ethical Guidelines for Medical and Health Research Involving Human Subjects in Japan.

RESULTS

All four patients completed the program without adverse events. Adherence to supervised sessions was high, and self-training was performed in all cases. Perceived exertion improved in all patients. Changes in HR responses were variable. Three patients returned to school after discharge, and two attended more than three days per week (Table 2).

Table 2. Clinical outcomes before and after the intervention.

	VAS (mm)		Heart rate at rest (bpm)		Fluctuations in heart rate in AS from the supine position (bpm)		Fluctuations in heart rate in ST from the supine position (bpm)		School attendance after discharge
	Pre	Post	Pre	Post	Pre	Post	Pre	Post
P1	86	46	80	80	40	34	38	32	Daily attendance
P2	78	30	65	77	NA	24	43	25	≥3 days/week
P3	84	60	70	85	45	30	43	30	Every other day
P4	82	61	73	81	9	8	21	21	unable

VAS: visual analog scale; AS: active standing; ST: standing on a tilt table; NA: not applicable.

Patient 1 was an 11 year-old male (150 cm, 30 kg) with delayed early development. From the age of 9 years, he experienced monthly episodes of dizziness of unknown cause that occurred mainly in the morning and resolved by the afternoon. By the age of 10 years, the symptoms had worsened and sometimes prevented him from getting out of bed. On days when he was able to attend school, he often returned home because of malaise. By the age of 10 years and 6 months, the frequency of symptoms had increased to approximately five times per week, leaving him bedridden on most mornings and unable to attend school. A Head-up Tilt Test (HUT) demonstrated a 50 beats per min (bpm) increase in heart rate within 1 minute of standing, which met the pediatric diagnostic criteria for postural orthostatic tachycardia syndrome (POTS). His Gross Muscle Test (GMT) score was 4/4, and his Functional Independence Measure (FIM) score was 113. At baseline, his heart rate was 80 bpm in the supine position, 120 bpm during active standing (AS), and 118 bpm during tilt table standing (ST), corresponding to fluctuations of 40 bpm and 38 bpm, respectively. After 14 days of rehabilitation, his resting heart rate remained unchanged; however, the heart rate fluctuations decreased to 34 bpm during AS and 32 bpm during ST. His Visual Analog Scale (VAS) score improved from 86 mm to 46 mm. One week after discharge, he was able to attend school daily, purchased an ergometer, and continued self-rehabilitation at home.

Patient 2 was a 14 year-old female with no previous medical history who had chronic difficulty waking in the morning because of abdominal pain and headache, often sleeping until noon. Baseline evaluation showed a resting heart rate of 65 bpm and 108 bpm during ST, corresponding to an increase of 43 bpm, which fulfilled the diagnostic criteria for POTS in adolescents. After 10 days of rehabilitation, her HR fluctuation during ST decreased to 25 bpm, and her VAS score improved from 78 mm to 30 mm.

Patient 3 was a 13 year-old male (159 cm, 52 kg) with no prior medical history. Since the age of 11 years, he had trouble getting up in the morning. He felt normal in the supine position but developed dizziness when sitting or standing. By the age of 12 years and 2 months, symptoms occurred almost daily, and he attended school only after 10:00 AM. By the age of 12 years and 8 months, he spent most mornings bedridden and was unable to attend school. He exhibited orthostatic symptoms with a marked drop in blood pressure immediately after standing and a recovery time of 45 seconds. His initial HUT showed a HR increase of 24 bpm, leading to a provisional diagnosis of orthostatic hypotension. However, repeat testing demonstrated a HR increase of 47 bpm, which met the pediatric diagnostic criteria for POTS. His GMT and FIM scores were 4/4 and 106, respectively. At admission, his heart rate was 70 bpm in the supine position, 115 bpm during AS, and 113 bpm during ST, corresponding to fluctuations of 45 bpm and 43 bpm respectively. After 13 days of rehabilitation, his resting HR increased to 85 bpm while HR fluctuations decreased to 30 bpm during AS and 30 bpm during ST. His VAS score improved from 84 mm to 60 mm. After discharge, he attended school every other day and performed supine stretching exercises on days when he was unable to get out of bed.

Patient 4 was a 13 year-old female with long-standing school absenteeism due to orthostatic intolerance (OI). She had suspected selective mutism and autism spectrum disorder, although no formal diagnosis had been made. During HUT, her heart rate increased from 73 bpm at rest to 93 bpm during ST (increase of 20 bpm). Although this did not meet the diagnostic criteria for POTS, she fulfilled the diagnostic criteria for OI because she had chronic orthostatic symptoms, daily functional impairment, and reproducible symptom provocation during standing without an alternative explanation. After 11 days of rehabilitation, HR fluctuations remained similar (8 bpm during AS and 21 bpm during ST); however, her VAS score improved from 82 mm to 61 mm.

DISCUSSION

This feasibility case series demonstrated that a short-term inpatient supine ergometer program was safe, well tolerated, and implementable in pediatric patients with orthostatic intolerance. All four participants completed the intervention without adverse events, and adherence to supervised and self-training sessions was high, indicating good acceptability of the protocol. Improvements in perceived exertion were observed consistently, whereas changes in heart rate responses during standing tests were variable. Although three patients returned to school after discharge, the frequency of attendance differed among individuals. These findings suggest that a brief supine exercise program may serve as a feasible initial rehabilitation approach for adolescents with OI who have difficulty engaging in upright exercise. Although lower-limb exercise, such as walking, is recommended, no established therapy currently exists for adult or pediatric OI. Exercise is considered key to recovery⁶⁾, and it is recommended to begin in a supine or semi-lateral position and gradually increase intensity through warm-up, exercise, and cool-down phases. Periodic reconditioning is central to OI treatment, particularly in chronic disease, where reduced cardiovascular function may worsen disability¹⁹⁾. Structured programs combining endurance and resistance training have been reported¹⁹⁾, and recent evidence in adolescents with POTS has shown that structured exercise training can improve circulatory dynamics and autonomic regulation²⁰⁾. However, therapy remains challenging in OI because deconditioning itself is part of the pathological process²¹⁾. Therefore, we developed a supine exercise regimen and initiated this pilot study. Most patients were able to resume school attendance, although the frequency varied among individuals. Only one patient, who was able to attend more than three days per week, was suspected of having a developmental disorder. Previous research suggests that school refusal may be related to autonomic dysfunction and sensory hypersensitivity⁴⁾. In addition to OI, we believe that the patient’s absence may also have been associated with a developmental disorder, which may explain the discrepancy between the VAS scores and the hemodynamic findings.

This case study has several limitations. First, the small sample size and single-center design introduce potential institutional bias and limit the generalizability of the findings. Second, the absence of a control group precludes causal interpretation, and the observed improvements may reflect factors other than the intervention itself, such as hospitalization, structured daily routines, reduced stress, or increased supervision and support. Third, psychological and developmental factors were not systematically assessed, despite previous reports indicating their potential relevance in patients with orthostatic intolerance²²⁾. These factors may have influenced both symptom perception and functional outcomes, including school attendance. Future studies should incorporate standardized psychological and developmental assessments. Additionally, the cardiac autonomic nervous system was not sufficiently evaluated; factors such as adrenergic receptor sensitivity may contribute to the observed responses²³⁾. Furthermore, compliance with exercise therapy was assessed only during hospitalization, and no long-term follow-up data were available to evaluate sustained effects. Finally, although feasibility and safety were demonstrated, objective physiological improvements were limited and inconsistent, and the conclusions rely primarily on subjective measures and school reintegration outcomes. Further studies are required to assess the long-term durability and efficacy of this intervention²⁴⁾.

Supine ergometer exercise appears to be a feasible and safe rehabilitation strategy for pediatric OI. Further controlled studies are needed.

Funding

The authors did not receive any funding.

Conflict of interest

The authors declare no conflicts of interest.