Athletic hip and groin pain:

Hip and groin pain presents an enormous challenge for practitioners involved in diagnosis, rehabilitation and prevention. The complex anatomy, along with a lack of understanding of the aberrant mechanisms that predispose an athlete to injury makes the management of these injuries notoriously difficult. A systematic review evaluating risk factors for groin injury identified four key factors that might predispose an individual to injury: a previous history of groin injury, reduced hip adductor strength (absolute and relative to hip abductor strength), more elite levels of competition and lower levels of sport-specific training (Emery et al 2015). These injuries are a significant burden to professional team sports. A recent meta-analysis demonstrated that hip, groin and pelvis injuries accounted for 28.3% of all injuries in men’s ice hockey (Szukics et al 2022). While in elite level soccer these injuries account for between 13 and 20% of all injuries (Sherman et al 2018).

The etiology of hip and groin injury remains poorly understood, at a fundamental level these injuries typically occur as a disconnect between the load (both acute and cumulative) that the region is exposed to, and the capacity of both the contractile and non-contractile tissues. Certain injuries will require that these tissues are unloaded and rested, while others demand an increase in tissue capacity. For this reason, rehabilitation methodologies that are capable of impacting muscle, tendon and boney tissue, and that are a low mechanical cost, are of great interest in the management of groin injury.

Blood flow restriction training:

Blood flow restriction training has recently gained popularity as a method for increasing muscle mass and strength using resistance training loads as low as 20% 1RM. Traditional resistance training methods typically demand loads greater than 70% 1RM be used in order to trigger a muscle hypertrophy response, making BFR an appealing alternative. The use of BFR in musculoskeletal and clinical rehabilitation is rapidly becoming a critical part of gold standard care. To the authors knowledge there is currently no research exploring the use of BFR in the management of hip and groin injury, however, many of the core principles in the rehabilitation of these injuries indicate that BFR may be a useful strategy for several reasons.  

Above and below the cuff:

Most of the research surrounding the use of BFR training has targeted the muscles directly beneath the cuff. For example, the application of BFR cuffs to the most proximal part of the thigh has consistently been shown to increase quadriceps muscle mass and strength when training the lower limb. However, as we learn more about BFR, we discover that the benefits of this form of training may be pertinent to other areas of the body. Recent research from Eric Bowman has demonstrated an increase in muscle strength and endurance capacity in muscles located above the cuff in both the lower (2019) and upper (2020) limb. In the lower limb this research demonstrated increase in muscle strength in hip extension and abduction with the cuff placement at the top of the thigh. Likewise, Constantinou et al (2022) demonstrated a significant increase in hip extensor strength following 4 weeks of BFR training, compared to traditional heavy resistance exercise in individuals suffering from patellofemoral joint pain. These findings suggest that BFR may be a viable strategy to improve the capacity of the tissues that surround the hip and lumbopelvic region and be a useful strategy in managing complex hip and groin injury.

Hip torque ratios and muscle strength:

The muscles surrounding the lumbo-pelvic-hip complex work synergistically to balance the pelvis and create movement. This region acts as a central hub for load transfer during all movements and is often subject to forces up to 15x body weight during high-intensity efforts such as sprinting and change of direction. There is good evidence to suggest that both the absolute strength of these muscles, along with their relative strength and balance across the pelvis is important in managing and rehabilitating hip and groin pain. For example, there is strong evidence that the relationship between hip adduction and abduction strength (referred to as the ADD:ABD ratio) is important in managing and preventing hip and groin pain. The precise desired ratio depends on the research and is likely influenced by the athlete population and the demands of the sport, however generally speaking to create balance across the pelvis the hip extensors should be the biggest producers of force across the hip closely followed by the hip flexors, and the hip adductors should be slightly stronger than the hip abductors. Depending on the nature of the injury will determine whether it is the more dominant or weaker structures that are subject to injury. Regardless, optimizing strength balance across the pelvis requires intelligent programming. In order to change the peak force generating capacity of a muscle, we typically require high-intensity resistance training methods which in conditions of hip and groin pathology can be highly provocative. While we currently lack evidence directly exploring the use of BFR in optimizing hip torque ratios and improving athlete outcomes in hip and groin rehabilitation, BFR training has been shown to improve the strength and capacity of the hip extensor, hip flexor and hip abductor muscle groups. By providing a low-cost alternative to traditional resistance training that may be better tolerated by injured athletes, BFR offers a training solution to expedite the desired improvements in maximum strength and hypertrophy of muscle that support the hip and pelvis. General guidelines for prescribing BFR training to achieve improvements in muscle strength and hypertrophy are outlined below. To achieve sustained improvement the program should be progressed based on how each individual presents clinically and their desired training outcome. See Figure 1 for some more ideas.

Pain mitigation:

Many athletes managing hip and groin injury suffer from long-term chronic pain. Often the symptoms of hip and groin pain are not significant enough to remove the athlete from competition and symptoms are managed alongside training. In these cases, finding appropriate times to effectively load the muscles across the hip is limited, and the athlete risks further aggravation of symptoms and reductions in strength. Recent research suggests that performing light load blood flow restriction exercise may have a pain modulation effect. While there is growing evidence supporting the use of BFR in pain management, how and why it is effective remains speculative. Hughes et al. (2020) recently demonstrated that BFR may activate a hypoxia-dependent endocannabinoid pathway that plays a central role in exercise-induced hypoalgesia. Other proposed mechanisms include conditioned pain modulation and the preferential recruitment of high-threshold motor units. By temporarily relieving pain, the BFR stimulus might allow the athlete to complete more intensive traditional heavy resistance training methods pain free, or potentially train and compete in their sport with reduced pain levels. For more information on programming BFR for pain relief, check out our recent blog titled Blood Flow Restriction Training and the Athletic Knee.

Athlete load management:

As we previously discussed, the lumbo-pelvic-hip complex represents the central point of load transfer across the various kinetic chains within the body. Therefore, completing meaningful strength and power training sessions using traditional methods can often be problematic in athletes suffering from hip and groin pain, and other tissues within the body risk becoming deconditioned. While the research supporting BFR training in maximal muscle strength and hypertrophy is well recognized, BFR training may also be able to develop more high threshold training adaptations that are crucial to sporting performance. Eccentric strength is widely considered an essential physical quality in injury prevention and speed development. Changes in eccentric strength are typically reserved for training strategies that supersede an individual concentric 1RM such as the Nordic hamstring exercise. However, recent research from Jones et al. (2023) has demonstrated similar increases in eccentric hamstring strength using loads at 30%1RM + BFR when compared to 80%1RM eccentric training. Similarly, BFR training when combined with plyometric and speed training has been repeatedly shown to influence speed and power performance. When combined with practical BFR using elastic wraps 100m incremental runs led to a significant increase in 100m sprint time and isometric rate of force development performed on a leg press (Behringer et al 2010). Similarly, when combined with plyometric exercise, the application of BFR led to significant improvements in vertical jump performance, reactive strength and peak force at high contraction speeds in post-operative ACL patients (Demirci et al., 2020).

Take home messages:

Athletic hip and groin pain is a complex and multi-factorial injury, making prevention, diagnosis and rehabilitation a significant challenge. Blood flow restriction training presents as a potential strategy to positively impact rehabilitation and management via three key mechanisms:

1 -Providing a low-cost method to optimize torque ratios between muscles that cross the hip and pelvis. This may be achieved by improving the absolute strength levels of individual muscle groups or by improving the balance of strength across the pelvis.

2 – Providing symptomatic pain relief for athletes as a pre-loading or pre-training strategy.

3 – By maintaining high-threshold physical qualities such eccentric strength and leg power during periods or relative unloading.

References:

Whittaker, J. L., et al., Risk factors for groin injury in sport: an updated systematic review. British Journal of Sports Medicine, 2015. 49 (12): pp 803-809.

Szukics, P. F., et al., A Scoping Review of Injuries in Amateur and Professional Men’s Ice Hockey. Orthopedic Journal of Sports Medicine, 2022. 10 (4): pp 1-12.

Sherman, B., et al., Hip and Core Muscle Injuries in Soccer. American Journal of Orthopedics, 2018. 47 (10): pp 23-29.

Bowman, E. N., et al., Proximal, Distal, and Contralateral Effects of Blood Flow Restriction Training on the Lower Extremities: A Randomized Controlled Trial. Sports Health, 2019. 11 (2): pp 149-156.

Bowman, E. N., et al., Upper extremity blood flow restriction: the proximal, distal, and contralateral effects – A randomized controlled trial. Journal of Shoulder and Elbow Surgery, 2020. 29: pp 1267-1274. 

Constantinou, A., et al., Comparing hip and knee focused exercises versus hip and knee focused exercises with the use of blood flow restriction training in adults with patellofemoral pain. European Journal of Physical and Rehabilitation Medicine, 2022. 58 (2): pp 225-235.

Hughes, L., et al., The effect of blood flow restriction exercise on exercise-induced hypoalgesia and endogenous opioid and endocannabinoid mechanisms of pain modulation. Journal of Applied Physiology, 2020. 128: pp 914-924.

Jones, M. J., et al., Low Load With BFR vs. High Load Without BFR Eccentric Hamstring Training Have Similar Outcomes on Muscle Adaptation. Journal of Strength and Conditioning Research, 2023. 37 (1): pp 55-61.

Behringer, M., et al., Low-intensity Sprint Training With Blood Flow Restriction Improves 100-m Dash. Journal of Strength and Conditioning Research, 2010. 31 (9): pp 2462-2472.