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Eur J Appl Physiol
DOI 10.1007/s00421-015-3287-5
REPLY
An inability to distinguish edematous swelling from true
hypertrophy still prevents a completely accurate interpretation
of the time course of muscle hypertrophy
Felipe Damas1 · Stuart M. Phillips2 · Manoel E. Lixandrão1 · Felipe C. Vechin1 ·
Cleiton A. Libardi3 · Hamilton Roschel1 · Valmor Tricoli1 · Carlos Ugrinowitsch1
Received: 19 October 2015 / Accepted: 20 October 2015
© Springer-Verlag Berlin Heidelberg 2015
the experimental design are important and described in the
“Discussion” section of our article (Damas et al. 2015).
The explanation the authors provide in the letter is
already acknowledged in our manuscript: “Addition-
ally, DeFreitas et al. (2011) speculated that the significant
increase in muscle CSA that they found in the first week of
RT in untrained individuals was possibly [italics added for
emphasis] due to edema and could be falsely attributed to
hypertrophy; thus, they considered that the increased CSA
was indicative of hypertrophy only at week 3–4 (when it
was different from week 1)”. Since DeFreitas et al. did not
provide any measurement of edema it is not possible to
estimate the degree of edema that was present at the third
week of RT, and that was the main reason that we suggested
they might have overestimated the degree of increase in
muscle CSA. Importantly, the authors report an increase
in muscle CSA of 5.95 % at week 3, leading the reader to
believe that this was the actual magnitude of muscle hyper-
trophy. In their letter, on the other hand, they report (per-
haps more appropriately and realistically, in our opinion)
an increase in muscle CSA of around 2.41 % (under the
assumption that an unchanged amount of edema of 3.45 %
was present at this time), which was not clearly stated in
their manuscript. In addition, the authors include in their
original manuscript the minimal detectable statistical dif-
ference approach stating “…if an individual has a pre- to
post-training increase in CSA that is less than 3.37 % [and
estimate with an incredible degree of precision], then the
change was not real. The change in that scenario could
be attributed to the measurement error of the instrument.
However, an increase in CSA greater than 3.37 % (in total
change) should be attributed to the intervention, which is
typically resistance training”. It seems then that a large
assumption has been made by DeFreitas et al. that edema
is a constant fraction of the CSA measurement and their
Dear Editor,
DeFreitas et al. state that “The findings of Damas et al.
have not influenced the previously proposed time course
of skeletal muscle hypertrophy” with regard to our recent
publication (Damas et al. 2015). We appreciate the article
from DeFreitas et al. (2011), which depicts a theoretical
time course of muscle hypertrophy throughout a resistance
training (RT) program. In our view, we did not misinterpret
the findings of Defreitas et al., but instead we highlighted
the differences between our study protocol and theirs. As
can be read in our manuscript, both studies indicated sig-
nificant increases in muscle cross-sectional area (CSA)
around the third week of RT. However, our participants per-
formed only four previous RT bouts before the CSA assess-
ment (RT was performed twice a week), while DeFreitas
et al. (2011) used a three times per week RT; therefore
their participants performed around 9–12 RT bouts dur-
ing 3–4 weeks before measurements. These differences in
Communicated by Klaas R. Westerterp/Håkan Westerblad.
This reply refers to the letter available at
doi:10.1007/s00421-015-3286-6.
* Felipe Damas
felipedamas@usp.br
1 School of Physical Education and Sport, University of São
Paulo, Av. Prof. Mello de Morais, 65, São Paulo, SP
05508-030, Brazil
2 Department of Kinesiology, McMaster University, 1280
Main Street West, Hamilton, ON L8S 4K1, Canada
3 Laboratory of Neuromuscular Adaptations to Resistance
Training, Federal University of São Carlos, Rod. Washington
Luiz, km 235, SP310, São Carlos, SP 13565-905, Brazil
Eur J Appl Physiol
1 3
measurement error and they arrive, simply by subtraction,
at a ‘real’ hypertrophy of 2.41 % increase in muscle CSA
indicated by them in the letter to the Editor. We propose
that there may be, as we acknowledged in our paper, some
hypertrophy but due to an unknown contribution of edema
and the error of measurement even a 5.95 % increase in
muscle CSA is not interpretable as hypertrophy without
direct measurement.
We would like to reiterate that our findings do not
invalidate their time-course study; instead we suggest
their hypertrophy values might be overestimated. We high-
light that four bouts of RT (or even 9–12 bouts we con-
tend), performed during 2 weeks (or 3–4 weeks), are not
enough stimuli or time to promote whole muscle hypertro-
phy to the degree estimated and reported by ourselves or
by DeFreitas et al. Rather, our data including measurement
of edema, muscle damage markers and functional param-
eters indicate the increase in muscle CSA at this early time
point is largely attributed to edema-induced muscle swell-
ing (Damas et al. 2015). We propose that without empiri-
cal data or measurement of edema-induced muscle swell-
ing there can be no definite conclusion on the magnitude
of ‘real’ hypertrophy. When measured directly increases in
muscle fibre cross-sectional area are significant from pre-
training only at 7 weeks and not at 4 weeks (Green et al.
1999). Finally, we agree with the authors that the theme is
not closed, and a combination of both studies, analysing the
time course of muscle hypertrophy coupled with a measure
of edema would be indeed of upmost importance to gain
full understanding on resistance training-induced hypertro-
phy time course.
References
Damas F, Phillips SM, Lixandrao ME, Vechin FC, Libardi CA,
Roschel H, Tricoli V, Ugrinowitsch C (2015) Early resistance
training-induced increases in muscle cross-sectional area are
concomitant with edema-induced muscle swelling. Eur J Appl
Physiol. doi:10.1007/s00421-015-3243-4
DeFreitas JM, Beck TW, Stock MS, Dillon MA, Kasishke PR 2nd
(2011) An examination of the time course of training-induced
skeletal muscle hypertrophy. Eur J Appl Physiol 111(11):2785–
2790. doi:10.1007/s00421-011-1905-4
Green H, Goreham C, Ouyang J, Ball-Burnett M, Ranney D (1999)
Regulation of fiber size, oxidative potential, and capillarization
in human muscle by resistance exercise. Am J Physiol 276(2 Pt
2):R591–R596