Exploring immediate cardiorespiratory responses: low-intensity blood flow restricted cycling vs. moderate-intensity traditional exercise in a randomized crossover trial

Abstract

Purpose: Blood-flow restriction (BFR) endurance training may increase endurance performance and muscle strength similar to traditional endurance training while requiring a lower training intensity. We aimed to compare acute cardiorespiratory responses to low-intensity interval exercise under BFR with moderate-intensity traditional interval exercise (TRA).

Methods: We conducted a randomized crossover study. The protocol involved three cycling intervals interspersed with 1 min resting periods. With a 48-h washout period, individuals performed the protocol twice in random order: once as BFR-50 (i.e., 50% incremental peak power output [IPPO] and 50% limb occlusion pressure [LOP]) and once as TRA-65 (65% IPPO without occlusion). TRA-65 intervals lasted 2 min, and time-matched BFR-50 lasted 2 min and 18 s. Respiratory parameters were collected by breath-by-breath analysis. The ratings of perceived breathing and leg exertion (RPE, 0 to 10) were assessed. Linear mixed models were used for analysis.

Results: Out of the 28 participants initially enrolled in the study, 24 healthy individuals (18 males and 6 females) completed both measurements. Compared with TRA-65, BFR-50 elicited lower minute ventilation (VE, primary outcome) (-3.1 l/min [-4.4 to -1.7]), oxygen consumption (-0.22 l/min [-0.28 to -0.16]), carbon dioxide production (-0.25 l/min [-0.29 to -0.20]) and RPE breathing (-0.9 [-1.2 to -0.6]). RPE leg was significantly greater in the BFR-50 group (1.3 [1.0 to 1.7]).

Conclusion: BFR endurance exercise at 50% IPPO and 50% LOP resulted in lower cardiorespiratory work and perceived breathing effort compared to TRA at 65% IPPO. BFR-50 could be an attractive alternative for TRA-65, eliciting less respiratory work and perceived breathing effort while augmenting perceived leg muscle effort.

Trial registration: NCT05163600; December 20, 2021.

Keywords: Blood flow restriction training; Cardiorespiratory response; Cycling exercise; Healthy individuals; Interval training; Occlusion.

Fig. 1

Overview of the intermittent cycling protocol (A) with a detailed description of traditional endurance exercise (TRA-65) and blood-flow restriction endurance exercise (BFR-50) (B). IPPO: Incremental peak power output; * Cuff inflation/deflation (only during BFR-50)

Fig. 2

Flow chart: Three individuals could not be contacted anymore, and one individual had a hamstring injury that was not associated with the study. BFR-50: Blood-flow restriction endurance exercise; TRA-65: Traditional endurance exercise

Fig. 3

Time course of alterations in VE during intermittent cycling exercise as measured by BFR-50 (red) and TRA-65 (green). The annotation displays mean difference (95% CI) from linear mixed regression modeling. VE: minute ventilation; BFR-50: Blood-flow restriction endurance exercise; TRA-65: Traditional endurance exercise. The box plots display the median (line inside the box), interquartile range (IQR, edges of the box), and whiskers (lines extending from the box). Whiskers represent the range within 1.5 times the IQR from the 25th percentile (Q1—1.5IQR) to the 75th percentile (Q3 + 1.5IQR)

Fig. 4

Time course of alterations in oxygen consumption (VO₂) (A), carbon dioxide output (VCO₂) (B), tidal volume (VT) (C), and breathing rate (BR) (D) during intermittent cycling exercise, represented by BFR-50 (red) and TRA-65 (green). The annotation displays mean difference (95% CI) from linear mixed regression modeling. BFR-50: Blood-flow restriction endurance exercise; TRA-65: Traditional endurance exercise. The box plots display the median (line inside the box), interquartile range (IQR, edges of the box), and whiskers (lines extending from the box). Whiskers represent the range within 1.5 times the IQR from the 25th percentile (Q1—1.5IQR) to the 75th percentile (Q3 + 1.5IQR)

Fig. 5

Time course of alterations in the rating of perceived exertion breathing (RPE breathing) (A), the rating of perceived exertion leg (RPE leg) (B), and heart rate (HR) (C) during intermittent cycling exercise as BFR-50 (red) and TRA-65 (green). The annotation displays mean difference (95% CI) from linear mixed regression modeling. BFR-50: Blood-flow restriction endurance exercise; TRA-65: Traditional endurance exercise. The box plots display the median (line inside the box), interquartile range (IQR, edges of the box), and whiskers (lines extending from the box). Whiskers represent the range within 1.5 times the IQR from the 25th percentile (Q1—1.5IQR) to the 75th percentile (Q3 + 1.5IQR)