Who would have thought that cutting off blood flow to muscles could actually enhance athletic performance? Sports scientists have taken cues from surgeons who found that ischemic preconditioning (IPC)—repeated bouts of blood flow occlusion, and then releasing that occlusion—could optimize surgical outcomes if performed before surgery.
Now, that practice is being adopted by high performance athletes. However, a new study led by researchers at the KPE Human Physiology Research Lab has found that IPC does not enhance endurance performance during high-intensity cycling, regardless of whether applied five or 30 minutes before the activity.
In site of IPC’s growing adoption in the high performance sports world, the research, conducted by Dr. Ira Jacobs’ research team from the Faculty of Kinesiology & Physical Education, adds to the growing body of evidence that questions the practical benefits of IPC for endurance athletes. The study was a student research project conducted by former KPE undergraduate student Alex Isidori, now an MSc student at the University of Calgary.
IPC involves temporarily occluding blood flow to a limb using a pressure cuff, followed by a period of reperfusion—when blood flow is restored. This cycle is usually repeated a few times and is thought to offer performance benefits by protecting the body from ischemic stress. Some past studies have suggested IPC could improve exercise performance by enhancing muscle efficiency and oxygen delivery. However, evidence has been mixed, particularly for endurance sports like cycling.
The KPE study involved 14 recreationally active participants who completed as much work as possible while cycling for 10 minutes. Each participant completed the test on three separate occasions, under different conditions: once after IPC was applied five minutes before cycling, once after IPC was applied 30 minutes before, and once with no IPC at all (the control condition).
“The choice to use the five- and 30-minute intervals in our study was primarily based on the observations we published back in 2021 on methodological differences among IPC studies,” says Liam O’Brien, the KPE PhD student who guided Isidori (along with Professor Ira Jacobs, who directs the KPE Human Physiology Research lab and the Tanenbaum Institute for Science in Sport.) “We theorized that these methodological differences may contribute to the wide variability in response rates throughout the IPC literature. The studies we reviewed in that article showed that most IPC studies conducted exercise performance tests either immediately after (i.e., within the first 5 minutes) applying IPC or waited a period of approximately 30 minutes. There were a number of studies that had found performance enhancement when the IPC was applied within these intervals, so we were curious to compare each end.”
To induce IPC, participants had blood flow to their legs occluded using pressure cuffs inflated to ~220 mmHg—roughly the same pressure used to measure blood pressure—for five minutes at a time, repeated four times. In the control session, the same timing was followed but without occluding blood flow.
The results showed no significant differences in performance between the three conditions. Whether IPC was applied shortly before the test, 30 minutes in advance, or not at all, the cyclists completed similar amounts of work during their 10 minutes of cycling. Key physiological measures such as oxygen uptake (VO₂), heart rate, muscle blood volume, muscle oxygenation, and blood lactate levels also remained similar across all conditions.
IPC has been widely promoted as a non-invasive way to potentially boost athletic performance—a performance enhancing strategy that is not banned by sport governing bodies. However, the current study’s findings add to several others that suggest that IPC may not provide any real advantage for self-paced, high-intensity endurance events like short-distance cycling. This is particularly important information for athletes and coaches who may be considering adding IPC to their training or pre-competition routines.
The researchers also note that the effectiveness of IPC may depend on the type of exercise being performed. While it has shown promise in some sprint-based or longer-duration endurance tasks, this study suggests it may not translate to every sporting context.
“Performance enhancement is often hit or miss,” says O’Brien. “You can find several similar studies that indicate IPC absolutely does improve performance and others that find no performance enhancement whatsoever. While we have several theories, we still do not really know why certain individuals respond to IPC with performance enhancement whereas others do not. Because the response rates reported throughout the literature are so variable, I have learned to temper my expectations over whether IPC will or will not demonstrate performance enhancement.”
Although IPC is a burgeoning area of study in exercise science, the research team emphasizes the need for more rigorous and sport-specific testing before IPC can be recommended as a performance-enhancing strategy. Dr. Jacobs commented that when he has been asked by coaches and athletes about the effectiveness of IPC, he responds that it’s best to try to find out with each individual athlete in advance of competition whether or not they respond favorably to IPC. And both O’Brien and Jacobs advise that for now, athletes may be better off focusing on tried-and-true methods like proper training, nutrition, and recovery.
O’Brien says that the big picture on IPC largely depends on the population of interest. “IPC may be useful for providing an extra boost to performance in athletes, but may not be as worthwhile for the everyday exerciser,” he says. “In previous research, IPC has been shown to produce a performance improvement in the range of 1-4 %, which can mean the difference between a gold medal and missing the podium at the Olympics. But for a recreationally active person training for a 5k race, a 1-4 % improvement may not be as meaningful to their performance as well-structured training or a nutrition plan.” Furthermore, since IPC is a relatively time-consuming technique and can be uncomfortable, its use may be worthwhile for someone at peak shape looking to perform at a high level but may not be as worthwhile for “lower-stakes” athletes. “In either event, IPC has not been reported to worsen performance—so it is really a personal choice.”
This research was published in the Journal of Sports Sciences on April 8, 2025 and contributes to U of T’s ongoing commitment to evidence-based approaches in sports sciences and human performance.