The Acute Cardiorespiratory Response to Blood-flow Restricted Versus Traditional Exercise Training Regimens (CaRe BFR)

Detailed Description

This study investigates the acute physiological and perceptual responses to blood flow restriction (BFR) exercise compared with conventional endurance and resistance exercise in both patients with chronic obstructive pulmonary disease (COPD) and healthy individuals. The study consists of multiple experimental arms using randomized crossover designs to enable within-subject comparisons across exercise modalities and conditions.

Endurance Exercise - COPD Participants (Exhaustive Protocol)

Patients with COPD will complete three cycling exercise conditions in a randomized, crossover design:

Blood Flow Restriction Cycling (BFR-CYC)

Continuous Cycling (CONT-CYC)

Interval Cycling (INT-CYC)

All sessions will be performed on a cycle ergometer under standardized laboratory conditions, including a warm-up followed by the respective protocol. Exercise will be performed to symptom limitation (volitional exhaustion) unless predefined safety criteria are reached.

BFR-CYC: Continuous cycling at 50% peak work rate (PWR) with bilateral thigh cuffs inflated to 50% limb occlusion pressure (LOP). A maximum duration of 30 minutes is applied as a safety limit.

CONT-CYC: Continuous cycling at 65% PWR until symptom limitation.

INT-CYC: Interval cycling with repeated bouts at 80% PWR, interspersed with recovery periods at 50% PWR, until symptom limitation.

During all sessions, cardiorespiratory parameters (ventilation, oxygen uptake, carbon dioxide production), muscle oxygenation (NIRS), blood lactate, hemodynamic responses, and perceptual responses (dyspnea, perceived exertion) will be continuously measured.

Endurance Exercise - COPD and Healthy Participants (Fixed-Duration Protocol)

Both COPD patients and healthy participants will complete two endurance exercise conditions in a randomized, crossover design:

Blood Flow Restriction Cycling (BFR-CYC)

Non-BFR Control Cycling

All sessions will be conducted under standardized laboratory conditions on a cycle ergometer. Exercise will follow a fixed-duration protocol and will not be performed to volitional exhaustion, unless predefined safety criteria require early termination.

BFR-CYC: Three intervals of 2 minutes at 50% PWR, separated by 1-minute recovery periods, with bilateral thigh cuffs inflated to 50% LOP during exercise intervals.

Control: Time- and structure-matched protocol (3 × 2 minutes) without blood flow restriction at 65% PWR, with identical recovery periods.

During all sessions, cardiorespiratory, hemodynamic, and perceptual responses (dyspnea, perceived exertion) will be continuously measured.

Resistance Exercise - COPD and Healthy Participants (BFR vs Control, Fixed Protocol)

Both COPD patients and healthy participants will complete two resistance exercise conditions in a randomized, crossover design:

Blood Flow Restriction Resistance Exercise (BFR-RE)

Non-BFR Control Resistance Exercise

All sessions will be performed on a leg press device under standardized laboratory conditions. Exercise will follow a fixed set and repetition scheme and will not be performed to volitional exhaustion, unless predefined safety criteria require early termination.

BFR-RE: Unilateral right-leg press at 40% of one-repetition maximum (1RM) with cuffs inflated to 80% LOP. Protocol: 4 sets (30-15-15-15 repetitions).

Control: Bilateral leg press at 40% 1RM, 3 sets of 15 repetitions, without blood flow restriction.

During all sessions, cardiorespiratory, hemodynamic, and perceptual responses will be continuously measured.

Resistance Exercise - Healthy Participants (LOP Comparison Arm)

Healthy participants will complete two BFR resistance exercise conditions in a randomized, crossover design:

BFR at 40% LOP

BFR at 80% LOP

All sessions will be conducted on a leg press device under standardized laboratory conditions. Pneumatic cuffs will be applied to the proximal thigh of the right leg.

Participants will perform unilateral right-leg press exercise at 40% 1RM using a standardized protocol of 4 sets (30-15-15-15 repetitions) with fixed rest intervals. The protocol will be completed as prescribed (not to volitional exhaustion) unless predefined safety criteria require early termination.

Neuromuscular function will be assessed using maximal voluntary contraction (MVC) of the knee extensors measured before and immediately after exercise. Voluntary activation will be evaluated using the twitch interpolation technique with supramaximal electrical stimulation.

Inclusion and exclusion for the healthy participants are defined by the following criteria.

Inclusion criteria

• Age ≥ 18 years
• Clinically healthy

Exclusion criteria

• Physical or intellectual impairment precluding informed consent or protocol adherence
• Non-German speaking (precluding informed consent)
• Pain during exercise of any origin
• Pregnancy
• History of thromboembolic event in the lower extremity
• Resting systolic blood pressure <100 mmHg

Inclusion and exclusion for the COPD participants are defined by the following criteria.

Inclusion criteria

• Age ≥ 18 years
• Diagnosed COPD according to GOLD-guidelines12

Exclusion criteria

• Physical or intellectual impairment precluding informed consent or protocol adherence
• Non-German speaking (precluding informed consent)
• Acute or recent (within the last 6 weeks) exacerbation of COPD
• Pain during exercise of any origin
• Pregnancy
• History of thromboembolic event in the lower extremity
• Resting systolic blood pressure <100 mmHg