EXSC-510: Advanced Exercise Physiology Article Review
Reason for Article Choice and Importance
I selected the article “Damage and the repeated bout effect of arm, leg, and trunk muscles
induced by eccentric resistance exercises” due to the information in the last case study
assignment. (Chen et al., 2019) In the case study assignment, movement, and the scenario of Sara
complains of being very sore for 24-72 hours after working out with Tommy. I believe that Sara
is experiencing delayed-onset muscle soreness, however, as she continues to workout, she will
experience repeated bout effect. Delayed-onset muscle soreness is “muscle soreness that occurs
12 to 24 hours after an exercise bout.” (Powers et al., 2021) Repeated bout effect is “following
recovery from delayed-onset muscle soreness, a subsequent bout of the same exercise results in
minimal symptoms of muscle injury and soreness.” (p. 529b) I know that the more knowledge I
have on how muscles are affected, how the levels of plasma createine kinase and myoglobin play
a part in reactions in muscles, to workouts, specifically beginner level, the better I will be able to
help anyone that is new to working out, or returning to the gym. I know it will be beneficial to
the person I will be coaching if I am able to explain to him/her what they may experience after
their first workout, the best way to conteract any delayed-onset muscle soreness, what to do in
the future prior and after their workouts, and what to expect in future workouts. What better way
to learn the information then to zone in and specifically work the topic?
The importance of knowing about repeated bout effect and delayed-onset muscle
soreness, from the trainers’ standpoint, is so we can appropriately coach customers, for their
physical and mental benefit; to help them to prevent injury, and be able continue to workout in
the fashion that benefits them. Currently, according to Powers et al., there are a few different
theories to explain repeated bout effect, they are 1) neural theory; (2) connective tissue theory,
and (3) cellular theory. (p. 529b)
Introduction
Resistance exercise has been known to assist in strengthening of muscles, and increasing
flexibility. Resistance strength training exercise is recommended, especially for adults and the
older population, at least twice a week, involving all major muscle groups. The focus of this
study is on how eccentric exercises can improve muscle function, as well as other health
platforms; and to better understand the outcomes of eccentric focused workouts by
unaccustomed individuals. In past studies, it has been noted that eccentric exercises have resulted
in muscle damage, delayed-onset muscle soreness, as well as chemical changes in the blood,
such as muscle proteins (creatine kinase (CK)) and myoglobin.
Many different studies have shown to have conflicting information regarding muscle
damage, and repeated bout effect of leg and arm muscles, as well as limited information being
available.
Exercise induced muscle damage can also lead to rhabdomyolysis. In this study, the
authors want to look at the possibility of this occurring, however, according to other studies, the
changes in blood chemicals, creatin kinase (CK) or myoglobin, were detected to cause
rhabdomyolysis after one session of eccentric exercises. According to Merriam-Webster’s
medical dictionary, rhabdomyolysis is defined as the destruction or degeneration of muscle
tissue (as from traumatic injury, excessive exertion, or stroke) accompanied by the release of
breakdown products into the bloodstream and sometimes leading to acute renal failure.
(Rhabdomyolysis definition & meaning 2021)
This study compares nine resistance eccentric exercises using gym based machines, to
test for changes in delayed-onset muscle soreness (DOMS), creatine kinase (CK), myoglobin
(Mb), and maximal voluntary isometric contraction strength (MVC). These levels will be tracked
after the first and second bout of eccentric exercises. It was hypothesized that large increases in
plasma CK activity and Mb concentration would be found after the first but not the second bout.
Methods
With the use of nine different resistance training machines in a gym setting, 15 young
university male students, who lead a sedentary lifestyle and no recent injuries, were used for this
study. All participants performed the eccentric exercises that were selected for, this study. The
eccentric exercises were arm curl, elbow extension, chest press, leg extension, leg curl, standing
calf raise, lat pulldown, abdominal crunch, and back extension. These exercises were done
during the first and second bouts. The weight was set for 80% of MVC, and each participant did
5 sets of 10 repetitions of each exercise during each bout. The MVC load was determined by the
use of a load cell system that was implemented into each machine and connected to a data and
analysis system. This was measured bilaterally, then individually per side for each exercise.
MVC strength was charted immediately following the exercise in addition to that, MVC and
soreness levels were charted before and 1-5 days after the exercise session. Blood samples were
taken before and 1 – 5 days after each exercise bout to measure the creatine kinase activity and
myoglobin concentration levels. Participants were also instructed to drink 2L water each day for
the 7 days following exercise, and check urine color to avoid kidney failure. The reason for this
is to monitor kidney function, to avoid rhabdomyolysis.
The strength and weaknesses of the research study’s design is that it doesn’t specifically,
but does slightly indicate how the participant gets to the starting position of the eccentric portion
of the exercise. There also seems to be limited studies to compare the methods and results. This
study also seemed to reiterate written sections, such as the MVC instructions. Muscle soreness
didn’t seem to play a large part in this study in regards to what seemed to be the main focus of
the study since the first word of the title is “Damage and repeat bout effect”, though there is a
section and figure for this under the results section, however the main focus throughout the study
was on MVC.
Summary
Results of this study showed no significant differences in the baseline measures, however,
CK activity and Mb concentrations were highest after the first exercise bout. Regarding the
MVC for the muscle groups, results showed that the MVC strength decreased with greater
significance for the arm muscles then the other eight muscle groups. Muscle soreness was noted
after the first bout with no significant differences between dominant and non-dominant sides.
Muscle soreness was noted to be of significantly greater after the first bout, and with a less
significance after the second bout of eccentric exercises. Also, muscle soreness was more
significant in the arm than other muscle groups. In regards to CK activity and Mb concentration,
these levels were highest four to five days after the first eccentric exercise bout and did not
increase significantly after the second bout. Results state that no significant differences in regard
to muscles for MVC strength or soreness, however, in Figure 5 the knee extensors showed the
most difference between strength and soreness. Results also showed that the relation of MVC
strength decreased with increase in CK activity and Mb concentration, however, the study states
that there is no real correlation of CK activity and Mb concentration and muscle soreness.
Discussion
The hypothesis for this study was stated “that the magnitude of DOMS and decreases in MVC
strength after the first bout of eccentric exercise would be different among the muscles, but the
magnitude of the repeated bout effect would be similar among them.” The writers believe that
the findings were in line with the hypothesis, but that there were notable limitations to their
study. These limitations include that the participants were limited to only young males, indirect
markers of muscle damage, the time between exercise bouts, and the length of the exercise bout
at 4 hours. In comparison to previous studies, they found that CK activity and Mb concentration
increased after the first bout, which could suggest that these participants had greater muscle
damage, specifically to the arm muscles. MVC strength, muscle soreness, as well as CK and Mb
levels, were decreased after the second bout. It was also noted that CK and Mb levels after
performing eccentric exercises for the first time were indicative of rhabdomyolysis.
Conclusion
For novice exercisers, muscle damage is inevitable, especially after the first workout
session, however, with repeated bout effect, their muscles should not experience delayed-onset
muscle soreness as intense as the first time. Though CK activity and Mb concentrations will be
elevated after the first bout, additional exercise sessions should not increase these levels to such
extreme as to indicate rhabdomyolysis. It is also beneficial that everyone should have a
resistance strength training routine that includes eccentric exercises for better health, fitness, and
quality of life.
More research should be done to include a wide range of age groups and gender, to have
a more precise outcome and knowledge of how eccentric exercises cause muscle damage,
delayed-onset muscle soreness, and how repeated bout effect is beneficial.
Lara Malloy
EXSC 510
References
Chen, T. C., Yang, T.-J., Huang, M.-J., Wang, H.-S., Tseng, K.-W., Chen, H.-L., & Nosaka, K.
(2019, February 7). Damage and the repeated bout effect of arm, leg, and trunk muscles
induced by eccentric resistance exercises. Wiley Online Library. Retrieved December 11,
2021, from https://onlinelibrary.wiley.com/doi/10.1111/sms.13388.
Powers, S., Howley, E. T., & Quindry, J. (2021). Exercise physiology: Theory and application to
fitness and performance. McGraw-Hill.
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