New research finds MMA athletes experience more harmful changes to the blood than boxing, revealing bigger risks and a stronger need for athlete-specific recovery strategies.
Study: Changes in the rheological properties of blood in combat sports athletes (boxing vs MMA). Image credit: BioFoto/Shutterstock.com
A recent study analyzing blood viscosity and flow characteristics in combat sports athletes reveals that simulated MMA (mixed martial arts) sparring sessions lead to more pronounced changes in red blood cell deformability, aggregation, and plasma volume compared to boxing matches. The findings are published in Scientific Reports.
Background
Combat sports athletes frequently engage in dynamic sessions of direct confrontation. These sports, such as kickboxing, boxing, and MMA, rely on anaerobic processes during sessions and generate high physiological stress. This level of physical exertion induces substantial changes in the rheological properties of blood.
Rheological properties of blood refer to blood viscosity and flow characteristics. These properties are determined by the complex interplay between various blood components, such as plasma and red blood cells (RBCs). Blood viscosity is influenced by hematocrit (the percentage of RBCs), plasma viscosity, RBC deformability, and aggregation, which collectively affect blood flow in the body.
RBCs must be deformed to facilitate easy transport through narrow capillaries, ensuring cellular oxygen delivery. Physical exercise is known to either increase or decrease the deformability of RBCs and is thus expected to significantly impact blood’s rheological properties.
In the current study, researchers examined the rheological properties of blood in two groups of combat sports athletes, specifically those participating in boxing and MMA, and compared them with those of a control group of participants who led a sedentary lifestyle.
Study design
The study population included 16 boxers and 16 MMA performers who were elite-level athletes and regularly competed. The control group included 14 non-training men who led sedentary lifestyles.
Blood samples were collected from combat sports athletes before and after the dynamic sessions of direct confrontation (standardized simulated sparring, not official matches). Red blood cell deformability (elongation index at various shear stresses) and fibrinogen concentration were primarily determined, as these parameters are significant determinants of blood rheological properties.
The study was conducted during the preparatory period of training. All athletes were matched for age, training experience, and weight category. Environmental conditions were strictly controlled.
Study findings
The comparison between boxing and control groups before and after the combat session revealed an induction in RBC deformability at shear stresses of 4.24, 8.23, 15.95, 30.94, and 60.00 Pa among boxers.
This increase suggests that the training may stimulate the turnover of red blood cells, potentially enhancing deformability and oxygen delivery by replacing older cells with newer, more efficient ones.
The study also found an induction in boxer fibrinogen levels compared to that in control group participants. Physical exertion-induced induction in fibrinogen level leads to RBC aggregation, increasing blood viscosity.
However, there were no statistically significant changes in aggregation index or plasma viscosity in boxers, indicating that the increased RBC deformability may help maintain blood flow despite elevated fibrinogen levels.
A reduction in RBC deformability at shear stress 0.58 was observed in boxers compared to control participants. This may indicate mild RBC deformability impairment, potentially linked to oxidative stress from temporary tissue hypoxia or immune responses. A higher WBC level in boxers compared to controls further supports this notion.
In boxers, an increased WBC level and reduced RBC deformability at shear stress 2.19 were observed after the combat session. This suggests the activation of WBCs, which are stiffer and can alter blood circulation dynamics by interacting with RBCs through free radicals, thereby reducing their deformability.
By comparing the MMA and control groups before and after the combat session, the study found increased WBC, fibrinogen, and RBC deformability at shear stress 30.94 and 60.00 among MMA performers. The MMA group also observed a reduced RBC deformability at shear stresses of 0.58 and 1.13.
The study found significantly higher blood morphology indicators and RBC aggregation post-fight in the MMA group. The increased RBC aggregation observed post-fight in the MMA group potentially reflects a physiological response to elevated fibrinogen levels and inflammatory stress.
These findings collectively suggest greater disturbance and impairment in the rheological properties of blood in MMA athletes compared to boxers. The dynamic and comprehensive fighting techniques in MMA, including punches, kicks, knee strikes, grips, and chokes, cause more extensive injuries in larger areas of the body, including limbs and torso.
A much greater reduction in plasma volume was observed in the MMA group (~9%) compared to the boxing group (~1.6%), reflecting the prolonged duration and higher intensity of MMA sparring, which engages multiple muscle groups. A reduced plasma volume is a physiological response to intense physical activity, where fluid shifts from the intravascular space to working muscle tissues, resulting in hemoconcentration.
A significantly reduced plasma volume in the MMA group may indicate hemoconcentration-related changes in blood’s rheological properties, such as increased aggregation and decreased deformability of RBC. These combined effects may impair blood flow and reduce tissue oxygen delivery.
The authors note that the physiological changes observed after sparring are acute, but if repeated or unaddressed, could contribute to impaired blood flow and increased cardiovascular strain.
Study significance
The study reveals that simulated MMA fights have a more negative impact on the blood’s rheological properties than boxing matches.
This outcome may be influenced by MMA's more diverse and intense physical demands, which involve higher energy expenditure, greater tissue damage, and stronger inflammatory responses.
The study findings highlight the need for tailored hydration and recovery strategies in MMA to mitigate the adverse effects of hemoconcentration on athletic performance and recovery. Specific recommendations include strategies to minimize oxidative stress (e.g., antioxidant-rich diets and supplements), exercises that enhance vascular flexibility, and systematic blood parameter monitoring for combat athletes.
The study’s limitations include the use of simulated sparring rather than official competition, the inclusion of only elite male athletes, and a relatively small sample size. Further research is needed to confirm these findings in larger, more diverse cohorts and real tournament settings.
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