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Case Study: Athletes
Dr. Bosak
EXSC 510: Advanced Exercise Physiology
Raekwon J. Parker
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The two fraternal twins (Tommy & Jimmy) are each developing their physiques in their
distinct ways. By their choice of athletic endeavors, Tommy and Jimmy have ended up with
tremendously different aerobic and anaerobic energy systems. Jimmy wanted to be a marathon
runner (a distance sport that places long-term stress on the aerobic system) while Tommy
decided to be a shot-putter (a brief-duration, high-energy exercise that places bursts of energy on
the anaerobic system). Each requires a different physiological process involving slightly different
muscle composition, energy usage and metabolic processing. Their different training regimens
vary in terms of repetitions, duration, intensity, and frequency, all of which influence the
development of specific muscle fiber types. Some parts of the sport encourage extensive use of
type I muscle fibers (for example, long-distance runners), while others require type-II fibers
(shot-putters or sprinters). This is why each twin’s sport needs a well structured comprehensive
strength and conditioning program that adjusts the body’s primary energy systems and prepares
it to develop the muscle fiber that best suits the athletic needs.
Jimmy, one of the fraternal twins who is focusing on marathon training, will
predominantly engage in endurance workouts. Since Jimmy spends much less time training at
sustained, lower-intensity work (such as typical endurance workouts), his muscles are likely to
produce a higher percentage of Type 1 fibers, which exhibit slower-twitch characteristics.
Because these slow fibers contain more mitochondria and myoglobin than fast fibers, they are
better suited to the oxidative energy system, which stores and releases energy to support long-
duration, low-intensity exercise activities (Powers, 2018). As Jimmy's muscle fibers adapt to this
type of training, he will experience an enhanced capacity for fat metabolism and other
endurance-related physiological improvements. Through his endurance training, Jimmy will see
an enhancement in the amount of antioxidants in his muscles. His training will also lead to better
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cardiovascular efficiency, as evidenced by an increase in his maximum oxygen uptake
(VO2max) and the amount of blood his heart can pump with each beat (stroke volume), which
will occur alongside a reduction in his resting heart rate. These physical adaptations are expected
to significantly boost Jimmy's performance in long-distance running events.
Tommy, the twin who competes in shot put, will engage in strength training that demands
high intensity. His muscle composition will be skewed towards Type 2 fibers, which are fast-
twitch and supported by the anaerobic energy systems for ATP production (Powers, 2018). Shot
put requires the generation of substantial power in a brief period, and while Tommy may
experience fatigue more rapidly than Jimmy, he can also utilize ATP more swiftly for muscle
contractions. As a result of his training, Tommy's muscle mass is expected to increase as the rate
of protein synthesis exceeds that of protein breakdown, a dissimilar to the experience of his
brother Jimmy.
For athletes aiming to enhance their athletic abilities, the force production plays a crucial
role in their progress. The persistent need for a certain level or kind of force output will influence
which muscle fiber type becomes more prevalent in an individual's muscles. Type 1 muscle
fibers, also known as “slow”-twitch fibers, contract more gradually compared to Type 2 muscle
fibers, which are “fast”-twitch. This variance in contraction speed is a key reason why Jimmy is
expected to have a higher proportion of Type 1 muscle fibers because of his sport as a long
distance marathon runner, while Tommy is likely to have a greater abundance of Type 2 muscle
fibers because of his position as a short burst explosive shot putter .
Tommy will rely more heavily on the anaerobic glycolysis system due to his training
focused on producing significant force, which will lead to a more frequent use of his Type 2
muscle fibers compared to those of Jimmy. The anaerobic glycolysis pathway is crucial for
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supplying ATP during short, intense bursts of exercise, a type of activity that is not a regular part
of Jimmy's training regimen but is essential for Tommy's shot put events. Jimmy is not regularly
engaged in or trained for the type of competition that demands the energy system in question; on
the other hand, Tommy is dedicated to mastering an event that necessitates proficiency in this
particular energy system.
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References
Powers, S.K. and Howley, E. T. (2018) Exercise Physiology: Theory and application to
fitness and performance (10th Ed.). McGraw Hill
Raekwon J. Parker
