Blood-Flow–Restricted Strength Training Combined With High-Load Strength and Endurance Training in Pulmonary Rehabilitation for COPD: A Case Report

Abstract

Objective

The purpose of this report is to describe the case of a patient with chronic obstructive pulmonary disease (COPD) who was load compromised and being referred for outpatient pulmonary rehabilitation. Low-load blood flow restriction strength training (LL-BFRT) was applied to prepare for and increase tolerability of subsequently applied high-load strength training.

Methods (Case Description)

A 62-year-old woman with COPD GOLD 2 B presented with severe breathlessness. Lower limb strength was severely reduced while functional exercise capacity was preserved. The patient was severely load compromised and had high risk to be intolerant of the high training loads required to trigger the desired adaptations. LL-BFRT was applied during the first 12 training sessions and high-load strength training in the subsequent 12 training sessions of the rehabilitation program. Endurance training on a cycle ergometer was performed throughout the program.

Results

Symptom burden in the COPD assessment test was reduced by 6 points (40%). Lower limb strength improved by 95.3 Nm (521%) and 88.4 Nm (433%) for the knee extensors and by 33.8 Nm (95%) and 56 Nm (184%) for the knee flexors, respectively. Functional exercise capacity improved by 44 m (11%) in the 6-minute walk test and 14 repetitions (108%) in the 1-minute sit-to stand test. The patient did not experience any adverse events related to the exercise training.

Conclusion

Clinically relevant changes were observed in both strength-related functional and self-reported outcomes. The achievements translated well into daily living and enabled functioning according to the patients’ desires. LL-BFRT was reported to be well tolerated and implementable into an outpatient pulmonary rehabilitation program.

Impact

The description of this case encourages the systematic investigation of LL-BFRT in COPD. LL-BFRT has the potential to increase benefits as well as tolerability of strength training in pulmonary rehabilitation. Consideration of the physiological changes achieved through LL-BFRT highlights potential in targeting peripheral muscle dysfunction in COPD.

Blood Flow Restriction Exercise, COPD, Functional Exercise Capacity, Pulmonary Rehabilitation, Strength Training

Background and Purpose

Chronic obstructive pulmonary disease (COPD) is characterized by respiratory symptoms (ie, dyspnea, cough, and sputum) and airflow obstruction.¹ As a systemic consequence of the disease, losses in muscle mass and function occur, considerably affecting exercise and functional capacity, health-related quality-of-life, and survival.² Targeting these impairments and the underlying peripheral muscle dysfunction, pulmonary rehabilitation is considered the method of choice.^2,3 Pulmonary rehabilitation is delivered in a multimodal way (ie, including exercise training, educational modules, and smoking cessation and nutritional counseling as needed).⁴ Despite pulmonary rehabilitation effectively ameliorating symptoms, exercise capacity, and health-related quality-of-life,³ peripheral muscle dysfunction remains a persistent problem in COPD, leading to a vicious circle of breathlessness and deconditioning.² Furthermore, uptake of pulmonary rehabilitation programs is low and dropout rate high.⁵ In search of explanations, the high training loads required to induce adaptations in the skeletal musculature of COPD patients are suggested.² Patients with COPD, already in mild to moderate stages of the disease, suffer from an early ventilatory limitation during activity, which compromises exercise training load tolerance.⁶ Thus, the American Thoracic Society and the European Respiratory Society (ATS/ERS) emphasize the need for novel interventions targeting peripheral muscle dysfunction in COPD.²

Low-load blood flow restriction strength training (LL-BFRT) may increase benefits and tolerability of exercise training in load compromised populations by reducing arterial inflow and preventing venous outflow of the targeted skeletal muscle, which leads to a localized hypoxia and metabolite pooling that stimulates skeletal muscle strength and hypertrophy.⁷ In LL-BFRT, training loads as low as 20% to 30% of the 1-repetition maximum (1 RM) achieve equal strength and muscle mass gains as high-load strength training (HL-ST) (60% to 80% of 1 RM).⁷ To date, no studies or case reports on the use of LL-BFRT in COPD are available. LL-BFRT was extensively investigated in healthy elderly, those with various musculoskeletal conditions, and in selected cardiac conditions and proven to be safely applied.⁸

We present the case of a load-compromised COPD patient being referred for outpatient pulmonary rehabilitation in which we applied LL-BFRT to prepare for and increase tolerability of a subsequent HL-ST and endurance training program.

Methods: Case Description

Participant

A 62-year-old retired woman was referred to our center for outpatient pulmonary rehabilitation. The patient was diagnosed with COPD GOLD 2, risk class B, according to GOLD-guidelines,¹ and relevant comorbidities were fibromyalgia and osteopenia. The COPD was in a stable condition with the patient abstaining from smoking, experiencing the last acute exacerbation approximately 1 year prior to training. Medical treatment was according to guidelines without any adjustment at baseline or during the intervention (inhaled olodaterol/tiotropium bromide 2.5 mcg, 2 puffs in the mornings).

The patient’s main complaint was breathlessness, preventing her from climbing more than 20 steps at once and disabling her to carry items (eg, laundry basket, grocery) to her apartment. Additionally, intermittent joint pain in the knees, wrists, and fingers was present, which she feared might be exaggerated during exercise training.

Assessment Procedure

To measure initial training load determination and for progress monitoring, patients referred for pulmonary rehabilitation undergo a standardized baseline and follow-up assessment procedure at our center.

Cardiopulmonary exercise testing (CPET) was performed in accordance with published guidelines.⁹ A bicycle ergometer with an incremental ramp protocol (10 Watts/min) was used.

Lung function testing was performed according to ATS/ERS guidelines.¹⁰ Forced expiratory volume in 1 second, forced vital capacity, and lung diffusion capacity of carbon monoxide were obtained after short-acting bronchodilator application.^10,11

Isometric muscle strength of the knee extensor and flexor musculature was assessed by handheld dynamometry using the “break technique.”¹² Measurements were performed using a standardized protocol. Moment arms were recorded to express the results as torque measurements in Newtonmeters (Nm) and % predicted.¹²

The 6-minute walk test (6MWT) was performed according to ATS/ERS technical standards.¹³ The walking distance was documented at the end of the test.

The 1-minute sit-to-stand test (1MSTS) was performed using a standardized protocol.¹⁴ The number of sit-to-stand repetitions was documented.

Dynamic strength was quantified through 1-RM estimation from submaximal RM testing (1 RM predicted = |$\frac{weight\ lifted}{1.0278-0.0278\times the\ number\ of\ reps\ performed}$|⁠).¹⁵ Results were recorded in kilograms.

Symptom burden was assessed by the COPD assessment test (CAT).¹⁶

Arterial occlusion pressure (AOP) was determined through Mini-Doppler measurements of the Arteria dorsalis pedis at the first and eighth training session and was used to identify the occlusion pressure needed for LL-BFRT. AOP was identified to the nearest ±5 mmHg.

Clinical Reasoning

The patient presented with a respiratory limitation in CPET, showing reduced oxygen uptake (VO_2peak = 15.3 mL/kg/min; 73% predicted) and work capacity (76 W; 76% predicted). Lower limb strength was severely compromised, with a knee extensor strength of 18.3 Nm in the right leg and 20.4 Nm in the left leg. Knee flexor strength was 35.4 Nm in the right leg and 30.4 Nm in the left leg. In contrast, functional capacity was preserved with a 6MWT distance of 468 m and a 1MSTS of 13 repetitions. However, the patient presented with severe symptoms (CAT-score of 15 points) and considerable limitations in daily living. We interpreted the low muscle function as a possible cause for the severe breathlessness in demanding tasks (such as stair climbing). Considering our assessments, we concluded that the patient was severely load compromised and had high risk to be intolerant of the high training loads required to trigger the desired adaptations.

In absence of contraindications for LL-BFRT, such as thromboembolic events, polyneuropathies, and low resting blood pressure, we designed an individually tailored program incorporating LL-BFRT (Fig. 1). The patient provided written consent to take part in this experimental approach.

Figure 1

Rehabilitation setup including assessment procedures. AOP = arterial occlusion pressure; CPET = cardiopulmonary exercise testing; FEC = functional exercise capacity; HL-ST = high-load strength training; LL-BFRT = low-load blood flow restriction strength training; PA = physical activity.

Intervention

Pulmonary rehabilitation was performed in accordance with clinical practice guidelines.⁴ The patient performed strength and endurance-type exercises for 24 sessions with 2 sessions per week. The sessions took place on Tuesday and Thursday mornings, ensuring sufficient recovery. In addition, 3 lessons of education took place (topics were general disease knowledge, dyspnea management, and physical activity). We modified the strength program so that during the first 12 training sessions load was low using LL-BFRT, and thereafter, HL-ST was incorporated. LL-BFRT was applied bilaterally to the exercises of the lower limb: plate-loaded leg press and leg extension machines (Fig. 2). Initial training loads were determined through 1-RM estimation.¹⁵ Both exercises were performed in random order. However, at least a 5-minute break was ensured between the exercises. Data on adverse effects (ie, intolerable muscle soreness, vascular problems, joint pain, skin bruises, etc) were documented at each training session by the treating physiotherapist.

Figure 2

Application setup of the low-load blood flow restriction strength training (LL-BFRT) (example picture) on plate-loaded leg press (left) and knee extension (right) machines.

Low-load Blood Flow Restriction Training

LL-BFRT was performed in accordance with available evidence-based application guidelines to enhance muscle strength.⁸ An AOP of 70% was applied using manually inflatable cuffs (Slim Cuff [width 11 cm] and Hand Inflator with Manometer, VBM Medical, Sulz a. N., Germany) at the most proximal part of the thighs bilaterally. Low-load strength training at 30% of the 1 RM was applied. Each exercise consisted of a total of 75 repetitions during 4 sets. The first set covered 30 repetitions and the subsequent sets 15 repetitions each. Training rhythm was set at 1–0–1-0 (ie, 1-second concentric phase, no pause, 1-second eccentric phase, no pause). Training load was increased per exercise every time ≥33 repetitions were achieved in the first set. Training load was decreased if muscle failure was reached before achieving 27 repetitions in the first set. During the subsequent 3 sets, training load was not changed. Pilot work was used to establish these threshold values. The breaks between the sets were standardized to 45 seconds. During the breaks, the patient remained seated, and occlusion pressure was not lowered. After the exercise, the cuff was deflated and removed. An overview of the strength training programming according to the Frequency, Intensity, Type, Time components is provided in Table 1.

Table 1

FITT Components of the Strength Training Intervention^a

		LL-BFRT Phase	HL-ST Phase
Frequency		2×/wk, 12 trainings per phase, Tuesday and Thursday mornings	2×/wk, 12 trainings per phase, Tuesday and Thursday mornings
Intensity	Volume	4 sets with total 75 repetitions (30, 15, 15, 15 repetitions) under BFR	3 sets with total 24–36 repetitions (8–12 RM each)
	Initial load	30% of 1 RM	70% of 1 RM
	Rest	45 s between sets (cuff inflated), ≥5 min between exercises	60 s between sets, ≥5 min between exercises
	Progression	Volitional muscle failure ≥33 repetitions in first set	Volitional muscle failure ≥14 repetitions in any set
Type		Plate-loaded knee extension and leg press machines under BFR with 70% AOP	HL-ST: plate-loaded knee extension and leg press machines
Time		90 min per training session	90 min per training session

^aAOP = arterial occlusion pressure; BFR = blood flow restriction; FITT = Frequency, Intensity, Type, Time; HL-ST = high-load strength training; LL-BFRT = low-load blood flow restriction training; RM = repetition maximum.

High-load Strength Training

HL-ST was performed using the 3 set methodology, which was proven to be most effective in enhancing muscle strength.¹⁷ Each set was performed to muscular failure, which was aimed to be reached within 8 to 12 repetitions using 70% of the 1 RM. Training rhythm was set at 1–0–1-0. Training load was increased per exercise every time ≥14 repetitions were achieved in any set.¹⁷ Training load was decreased if muscular failure was reached before achieving 8 repetitions in any set.¹⁷ The breaks in between the sets were standardized to 60 seconds. During the breaks, the patient remained seated.

Endurance Training

Endurance training was performed using a continuous methodology on a stationary seated bicycle ergometer and lasted for 30 minutes. Target exhaustion was set at a Borg scale rating of 7 (numeric rating scale from 0–10) and was evaluated every 5 minutes throughout the exercise. Training intensity was raised if the patient’s mean exhaustion throughout 2 consecutive training sessions was less than Borg 7 and decreased if greater than Borg 7.

Outcomes

The patient did not experience an acute exacerbation of her COPD or an adverse event during rehabilitation. Compared with baseline, symptom burden was reduced by 6 points in the CAT score. Regarding functional exercise capacity, knee extensor strength improved by 95.3 Nm to 113.6 Nm in the right leg and by 88.4 Nm to 108.8 Nm in the left leg, respectively. Strength in the knee flexors was improved by 33.8 Nm to 69.2 Nm in the right leg and by 56 Nm to 86.4 Nm in the left leg, respectively.

The 1MSTS improved by 14 repetitions and the 6MWT distance by 44 m. No relevant changes in forced expiratory volume in 1 second, forced vital capacity, and lung diffusion capacity of carbon monoxide were observed. Baseline and follow-up values are presented in Table 2. Details on exercise training progression and exhaustion are shown in Supplementary Figures 1 and 2 for strength training and in Supplementary Figures 3 and 4 for endurance training. Details on the course of dynamic strength are shown in Supplementary Table 1 and on baseline CPET in Supplementary Table 2.

Table 2

Preintervention and Postintervention Values of all Assessment Variables^a

Variable	Value Preintervention	Value Postintervention	Change  (%)
CAT, points	15	9	−6 (40)
VO2peak, mL/min/kg (% predicted)	15.3 (73)	NA	NA
Peak work rate, W (% predicted)	76 (76)	NA	NA
FEV1, L (% predicted)	1.52 (64)	1.58 (67)	0.06 (3)
FVC, L (% predicted)	2.57 (86)	2.51 (84)	−0.06 (2)
TLCO, mmol/kPa/min (% predicted)	4.6 (63)	4.3 (59)	−0.3 (4)
Knee extensor strength, Nm right/left (% predicted)	18.3 (20)/20.4 (22)	113.6 (125)/108.8 (119)	95.3/88.4 (521/433)
Knee flexor strength, Nm right/left (% predicted)	35.4 (52)/30.4 (45)	69.2 (102)/86.4 (128)	33.8/56 (95/184)
6MWT, m (% predicted)	468 (92)	530 (103)	44 (11)
1MSTS, repetitions (% predicted)	13	27	14 (108)
1 RM leg press, kg	45.4	82.5	37.1 (82)
1 RM leg extension, kg	5.1	17.5	12.4 (243)

^aCAT = chronic obstructive pulmonary disease (COPD) assessment test; FEV₁ = forced expiratory volume in 1 second; FVC = forced vital capacity; 1MSTS: 1-minute sit-to-stand test; 6MWT = 6-minute walk test; NA = not applicable; 1 RM = 1-repetition maximum; TLCO = lung diffusion capacity of carbon monoxide; VO_2max = maximal oxygen uptake.

Regarding daily living, the stair-climbing ability of the patient improved by 25 steps without taking a break while carrying a filled laundry basket.

Discussion

We describe the first application, to our knowledge, of LL-BFRT in pulmonary rehabilitation for COPD. We observed impressive changes in both strength-related functional and subjective outcomes. The changes were most prominent in isometric knee extensor strength, which was our primary target in tailoring the pulmonary rehabilitation to the patient’s deficiencies. The minimal clinical important difference (MCID) of knee extensor muscle strength in patients with COPD undergoing pulmonary rehabilitation is considered to be 7.5 Nm.¹⁸ Our patient showed improvements of 95.3 and 88.4 Nm, corresponding to 13 and 12 times the MCID, respectively. In a recent meta-analysis, improvements in isometric strength of the knee extensor up to 32% were described from combined strength and endurance pulmonary rehabilitation programs.¹⁹ In the present case, this was outreached by far (strength change of 521% in the right leg and 433% in the left leg).

Besides the improvements in muscle strength, an increase in functional aerobic capacity (ie, the 6MWT) above the MCID of 30 m was observed.²⁰ The improvement of 44 m corresponds to the magnitude of change documented in the available literature.³ Baseline 6MWT distance already corresponded to 92% of the reference value and showed a normal value (103%) afterwards. Unfortunately, CPET after the program was not conclusively interpretable due to a mask leakage. In the 1MSTS, we observed substantial improvement of 14 repetitions, which is about 5 times the MCID. The 1MSTS is more strength dependent, while the 6MWT depends more on aerobic capacity^14,21; accordingly, the findings are in line with our hypothesis.

Interestingly, the course of weight used in LL-BFRT showed very little progression over time (Suppl. Fig. 1) with a short series of sessions where more load was tolerated. However, the training load had to be decreased due to task failure. Reasons for such task failure are unknown, and it remains to be shown if this is a common pattern during LL-BFRT in patients with COPD. However, we assume that LL-BFRT primed the muscles for HL-ST and enabled the continuous increases in training load.

The gains in muscle strength transferred well into daily living. The patient’s stair-climbing ability improved to her full satisfaction.

In addition, the patient reported substantially reduced COPD-related symptom burden (decrease in CAT-score of 6 points). No relevant changes in spirometry and lung diffusion capacity were observed in this patient suffering from moderately impaired airflow obstruction and diffusion capacity. Therefore, the improvements may be attributed to improvements in peripheral muscle function.

A limitation to our approach of applying LL-BFRT in combination with endurance training, as established in pulmonary rehabilitation, makes it difficult to distinguish the exact origin of improvement. Improvements in 6MWT and aerobic capacity in this case may be mostly due to the endurance component. Another minor limitation is not examining the oxygen saturation and blood pressure response during LL-BFRT. However, controlled designs and future studies may provide insight into the above minor limitations.

Since the nature of case reports does not imply generalizability, this case encourages the systematic investigation of LL-BFRT in COPD. The training regimen is novel in the field of respiratory diseases but is easily implementable using moderately priced material. From our experience, it shows potential to increase benefits and tolerability of strength training in pulmonary rehabilitation. Considering the physiological changes achieved through LL-BFRT, its potential in targeting peripheral muscle dysfunction in COPD becomes obvious. In detail, LL-BFRT has shown to induce more pronounced hypertrophy in type-1 muscle fibers and to increase satellite cell content to a greater extent compared with HL-ST.²²

In conclusion, the present case showed LL-BFRT to be well tolerated and implementable into a pulmonary rehabilitation program. We reported impressive improvements in objective and subjective outcomes when LL-BFRT was used as a preparation tool for HL-ST in a severely load-compromised woman with moderate COPD.

Patient Perspective

“The LL-BFRT training caused intense sensation of muscle burning and fatigue; however, the sensation diminished quickly when the cuff was removed. I certainly felt that my muscles were the main target of exercise. The breathlessness during LL-BFRT was easy to tolerate, and it was a relief for my joints that I did not need to lift that heavy weights. I felt much more confident to manage these when we shifted training regimens after 12 sessions.”

Author Contributions

Concept/idea/research design: D. Kohlbrenner, N.A. Sievi, C.F. Clarenbach

Writing: D. Kohlbrenner, C.F. Clarenbach

Data collection: D. Kohlbrenner, C. Aregger, N.A. Sievi, C.F. Clarenbach

Data analysis: D. Kohlbrenner, C.F. Clarenbach

Project management: C.F. Clarenbach

Providing participants: C.F. Clarenbach

Providing facilities/equipment: C.F. Clarenbach

Providing institutional liaisons: C.F. Clarenbach

Consultation (including review of manuscript before submitting): C. Aregger, M. Osswald, N.A. Sievi, C.F. Clarenbach

Funding

There are no funders to report.

Disclosures

The authors completed the ICMJE Form for Disclosure of Potential Conflicts of Interest and reported no conflicts of interest. C.F. Clarenbach reports personal fees from Roche, Novartis, Boehringer Ingelheim, GSK, Astra Zeneca, Sanofi, Vifor, Mundipharma outside the submitted work.