The Heart, Blood and Strongman - Episode 4: Blood Volume and Performance

Blood is more than a transport medium

For a Strongman athlete, blood is an active part of the performance system. It transports oxygen and nutrients, helps dissipate heat, maintains perfusion pressure and allows the heart to support the cardiac output required during exercise. Blood volume is therefore more than a laboratory number. It links the heart, vessels, muscle and thermoregulation.

Total blood volume consists mainly of plasma and the formed elements of blood, especially red-cell mass. These components do not change in exactly the same way and have different consequences for performance. Plasma directly influences circulating volume and venous return, while red cells largely determine oxygen-carrying capacity.

Plasma and red-cell mass

Plasma is the liquid portion of blood. It contains water, electrolytes, proteins and many molecules transported through the circulation. When plasma volume is well maintained, blood circulates within a sufficiently filled system and venous return to the heart can be supported.

Red-cell mass is the total amount of circulating red blood cells. Because hemoglobin in red cells binds oxygen, red-cell mass is linked to oxygen transport capacity. Performance, however, does not depend on hemoglobin alone. Cardiac output, peripheral oxygen extraction, hydration and muscle function also matter.

How does training affect blood volume?

Regular exercise can produce adaptations in plasma volume and fluid regulation. Repeated training can increase the body's capacity to retain water and sodium and to distribute circulating volume according to demand. Plasma-volume expansion is a recognized exercise-physiology adaptation, although its magnitude varies between individuals and training types.

In a strength athlete, these changes interact with large muscle mass, dietary intake, sweating and hydration strategies. Strongman does not impose the same circulatory demands as distance running, but it is not a purely anaerobic sport either: many events involve repeated effort, substantial circulation and thermal stress.

Blood volume and venous return

For the heart to pump effectively, it must receive blood. The amount of blood returning to the heart contributes to ventricular filling before contraction. In simple terms, sufficient circulating volume provides the cardiovascular system with the material needed to support cardiac output.

During exercise, this relationship is dynamic. The muscle pump, breathing and changes in vascular tone all influence venous return. When a Strongman athlete stops abruptly after a heavy carry, blood redistribution and vasodilation can rapidly alter venous return and blood pressure.

Why hydration can change performance

Fluid loss through sweating can reduce plasma volume. When the loss becomes substantial, circulating volume becomes less available and the cardiovascular system must work harder to maintain pressure and perfusion. In heat, the body must simultaneously send blood toward the skin for heat dissipation and toward active muscle for exercise.

This conflict is relevant in outdoor Strongman competitions, particularly in hot weather. Repeated sweating without appropriate fluid replacement can contribute to performance decline, greater cardiovascular strain and slower recovery.

Water is not the whole hydration strategy

Water is important, but fluid physiology cannot be reduced to plain water alone. Sodium and other electrolytes contribute to fluid distribution between compartments and to neuromuscular function. Sweat sodium losses vary substantially between individuals, so hydration strategies should be individualized according to environment, exercise duration and sweat rate.

For a Strongman athlete, an excessively aggressive hydration strategy can be just as inappropriate as inadequate intake. The goal is to maintain hydration compatible with performance and safety, not to chase a perfect body-weight number from one event to the next.

Hemoglobin and oxygen transport

Hemoglobin is the main oxygen carrier in blood. Total oxygen-carrying capacity depends heavily on hemoglobin concentration and on the total mass of hemoglobin in the body. This creates an important distinction between concentration and total amount.

When plasma volume expands, hemoglobin concentration can fall through dilution without a reduction in total hemoglobin mass. This is one reason an isolated hemoglobin value should be interpreted in the context of plasma volume and hydration status.

What does this mean for a very large athlete?

In a Strongman athlete with high body mass and substantial muscle mass, absolute circulatory demand is considerable. The heart must support perfusion of a large amount of active tissue, while blood flow moves through a vascular system that can shift quickly between vasoconstriction and vasodilation.

This is one reason general cardiovascular fitness matters even in a strength-dominated sport. An adapted heart, adequate circulating volume and good exercise tolerance can help an athlete repeat performance without disproportionate decline.

Blood volume and cardiac output

Cardiac output is the product of heart rate and stroke volume. Blood volume influences this system indirectly through venous return and cardiac filling. When venous return is well supported, the ventricles can use the Frank-Starling mechanism to adjust contraction according to filling volume.

In practical terms, circulating volume is one of the conditions that allows the heart to deliver blood effectively. It is not a separate switch for cardiac output, but part of the physiological context in which the cardiovascular pump operates.

What happens after a longer event?

After a longer event, especially in the heat, fluid losses can remain important after exercise has ended. Heart rate can remain elevated, core temperature may still be high, and the body continues to redistribute blood for thermoregulation and recovery.

That is why cardiovascular recovery between events is not simply about sitting down. Gradual recovery, cooling, appropriate fluids and electrolytes, and nutrition compatible with the competition schedule all matter.

More blood is not automatically better

More is not always better. Increased circulating volume within physiological adaptation can support performance, but pathological volume expansion or abnormal changes in blood composition can have negative consequences. Likewise, increasing red-cell mass should not be pursued artificially without medical indication.

This nuance matters in strength sports because some pharmacological interventions can alter hemoglobin, hematocrit and red-cell mass. A high value is not a biological trophy. It must be interpreted within the broader cardiovascular and hematological picture.

Plasma volume and recovery

Adequate plasma volume supports circulation during recovery. After exercise, the body must gradually restore water and electrolyte balance, and repeated exposure to dehydration can prolong fatigue and reduce the ability to reproduce performance.

In a competition with multiple events, small differences accumulated between events can become important by the end of the day. An athlete may enter the final event with apparently preserved muscular strength but with circulation and thermoregulation already compromised.

Why red-cell mass is not the same as hematocrit

Hematocrit is the proportion of blood volume occupied by red cells. It does not directly tell you how much total red-cell mass exists. If plasma volume expands, hematocrit can fall through hemodilution even when red-cell mass is unchanged or increased.

For this reason, a blood profile in an athlete should be interpreted with hydration status, sampling time and training context in mind. A single complete blood count cannot by itself describe the whole circulatory state.

What is the body actually trying to maintain?

The body is trying to maintain homeostasis. When blood volume falls, the kidneys, hormones and autonomic nervous system contribute to conserving water and sodium and maintaining pressure. When volume is adequate, the cardiovascular system can respond more flexibly to exercise and temperature changes.

In Strongman, this flexibility is valuable. Events are not identical, rest intervals vary, temperature changes, and cardiovascular demand can move rapidly from maximal effort to recovery.

Blood volume and repeated performance

Competition performance depends on more than a single peak-force event. The athlete must repeat efforts, recover, and enter the next event with a functioning cardiovascular system. Well-supported circulating volume can contribute to this chain through its effects on venous return, cardiac output and thermoregulation.

Blood volume can therefore be viewed as part of the hidden infrastructure of performance. It does not lift the weight for the athlete, but it helps the body keep delivering blood and managing stress between maximal efforts.

Conclusion

Blood volume influences performance through two major components: plasma volume, which supports circulating volume and venous return, and red-cell mass, which contributes to oxygen transport. Training, hydration, sweating, temperature and body composition continually change this balance.

For Strongman, a high-performing cardiovascular system is not only an adapted heart. It also requires enough circulating blood to fill that heart, support cardiac output, carry oxygen and enable thermoregulation. On a multi-event competition day, this infrastructure can become the difference between producing one huge effort and producing several strong efforts across the entire contest.

Selected bibliography

Sawka MN, Convertino VA, Eichner ER, Schnieder SM, Young AJ. Blood volume: importance and adaptations to exercise. Sports Med. 2000;29(3):149-159.

Convertino VA. Blood volume: its adaptation to endurance training. Med Sci Sports Exerc. 1991;23(12):1338-1348.

Montero D, Lundby C. Regulation of plasma volume in humans during and after exercise. J Physiol. 2017.

Sawka MN, Noakes TD. Does dehydration impair exercise performance? Med Sci Sports Exerc. 2007;39(8):1209-1217.

Kenefick RW, Cheuvront SN. Hydration for recreational sport and performance. Sports Sci Exchange. 2012.

Convertino VA. Cardiovascular consequences of exercise-induced blood volume reduction. Phys Sportsmed. 1987.