Running head: JOURNAL ARTICLE REVIEW 1
Fatigue Threshold in Exercise Physiology
Kanani Jackson
EXSC 510 Advanced Exercise Physiology
Liberty University
Dr. Kilian
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Fatigue Threshold in Exercise Physiology
In the journal of Medicine and Science in Sports and Exercise published by the American
College of Sports Medicine is an article called “Critical Power: An Important Fatigue Threshold
in Exercise Physiology” (Poole et al., 2016). I specifically chose this article because of my
interest in the fatigue threshold and how it can affect performance. The fatigue threshold may be
defined as the critical limit below which cracks cease to propagate under cyclic loading. The
fatigue threshold informs you where your body is in terms of performance, and just how much
further you should carry on. It’s a little like your body is waving the white flag, telling you to be
mindful that it has reached the point of fatigue and to avoid pushing a lot further. As the fatigue
threshold represents an important parameter in design and failure analysis much research effort
has been devoted during the last decades to revealing underlying principles (Poole et al., 2016).
In this article, there was a study linking fatigue and performance through critical power.
Previously, it had been thought the link between fatigue and performance was vague,
there is a curvilinear relationship between the time till the limit of tolerance is achieved and
constant speeds or power outputs (Poole et al., 2016). This article dives into the current
understanding of the critical power concept from a neuromuscular, metabolic, and cardiovascular
viewpoint while considering bioenergetics and performance-related consequences of navigating
critical power in healthy patients and those with chronic diseases.
This type of research seems to be weak because some of the research has a broad
similarity to rats (Poole et al., 2016). However, this article is simply using previously discovered
data to justify or link neuromuscular, metabolic, and cardiovascular components about
performance and then further into healthy and chronic disease-struck patients. The strength of the
research lies in the fact that the authors used a retrospective approach. This study is qualitative
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due to the use of data to confirm the concepts brought forth. The weaknesses lie in the similarity
to rats, the broad range of data analysis to cover, the lack of subjects used, and the multitude of
conclusions due to the broad data analysis (Poole et al., 2016). Had this article been a
randomized control trial, there would be a higher internal and external validity to the article
itself. A randomized controlled trial would have been easily accomplished since the focus
seemed to be on the healthy aging population versus a population with chronic diseases such as
chronic obstructive pulmonary disease (COPD) and chronic heart failure (CHF) (Poole et al.,
2016).
There were a multitude of conclusions reached. The first conclusion is that critical torque,
critical power, and critical speed create a neuromuscular fatigue threshold that separates exercise
intensity areas that have distinct fatigue mechanisms (Poole et al., 2016). However, there are
physiological factors that trigger the neuromuscular system into a new phase of behavior that is
unknown (Poole et al., 2016). It’s also unknown if the heavy and severe intensity categories have
clear boundaries of torque or power output each time which makes fatigue unpredictable,
creating a grey area (Poole et al., 2016). The second conclusion is that critical power and work
are sensitive to the influence of oxygen delivery, especially when hyperoxia increases critical
power while hypoxia and blood flow obstruction reduce it; in contrast, work is reduced in
hyperoxia, at high work rates in severe areas, exercise tolerance is decreased (Poole et al., 2016).
The critical power sets the boundary higher, and the slow component drives the VO2 to its max,
which loses the efficiency of how predictable how quickly muscle fatigue can set it (Poole et al.,
2016). The third conclusion is that the critical speed especially recruits microliters of oxygen to
low oxidative fast twitch muscles where the oxygen and oxygen uptake ratios are lower for slow
twitch muscles (Poole et al., 2016). In each person, recent evidence supports that critical power
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can be influenced by contraction characteristics (Poole et al., 2016). The fourth conclusion is that
work is the buffer to resist exercise intolerance during exercise that requires critical power, the
source of the buffer depends on the conditions; the lower the buffer the quicker an intolerance
and fatigue a person will appear (Poole et al., 2016). Critical power and work decline at about the
same rate across age and chronic disease, which puts the curve toward the origin (Poole et al.,
2016). Critical power was previously named the fatigue threshold, it marks the limit for fatigue
progression and work is the fatigue constant.
The discussion comes to an overall conclusion. The authors start with the fourth
conclusion and then work their way back up mentioning each little conclusion and linking them
together. The overall conclusion is that the power duration describes and precisely predicts
exercise performance (Poole et al., 2016). Critical power with work can assess if a particular
athletic feat or functional activity is doable for a particular person; it can be used to model ideal
performance strategies in teams where each athlete has different critical power and work values
(Poole et al., 2016). “For these reasons, the power-duration relationship may be considered
critical for understanding the limitations to human performance and fatigue processes that
underpin them” (Poole et al., 2016).
In conclusion, your fatigue threshold is simply the point in a workout or race at which the
body begins to experience a decline in performance. Not only that but critical power and
work/power duration abilities can predict fatigue. Typically, you can maintain Critical Power
for 30-60 minutes. Above the Critical Power, there's an amount of work you can perform
anaerobically. However, it seems that a similar feat was confirmed by VO2max testing in certain
activities. I think this could have been effectively accomplished in a randomized controlled trial
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along with the data that this journal article had already collected. While the connection might not
have been thought of until all these things were linked, it certainly made a splash.
Kanani Jackson
JOURNAL ARTICLE REVIEW
References
POOLE, D. A. V. I. D. C., BURNLEY, M. A. R. K., VANHATALO, A. N. N. I., ROSSITER, H.
A. R. R. Y. B., & JONES, A. N. D. R. E. W. M. (2016). Critical power. Medicine &
Science in Sports & Exercise, 48(11), 2320–2334.
https://doi.org/10.1249/mss.0000000000000939
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