In essence, tissue flossing creates conditions that are comparable to
localized tissue hypoxia, where muscles need to adapt to a lack of
oxygen. Although the partial vascular occlusion stimuli used in this
study are substantially shorter (3 x 3 minutes) compared to systemic
acute hypoxia stimulation, which is usually up to 40 minutes long, there
is some evidence that systemic hypoxia actualized via hypoxic chambers
can produce similar physiological responses to BFR
training \cite{Schoenfeld_2013}.
It has been suggested that the excitation of the sarcolemma remains
unaffected by systemic
hypoxia \cite{Kayser_1993,Rupp_2014}.
However, in a study where TMG parameters were used to assess muscle
contractile function at acute moderate altitude (hypoxia), an increment
of Tc and decrement of Dm was
registered \cite{Morales_Artacho_2015}.
In a recent study, \citet{Vogrin_2020} investigated the acute effects of a floss band applied over the ankle
joint on the TMG parameters of the gastrocnemius medialis muscle but
failed to find any statistically significant difference in TMG response.
The authors suggested that tissue flossing has a significant but
localized effect on the wrapped part of the body.
Similarly, the results of the present study show a significant
shortening in RF contraction time (Tc_RF) immediately after tissue
flossing intervention in the LOW condition and a medium effect in
Dm_RF in favor of the LOW condition compared to CON and HIGH. At the
same time, TMG parameters remained virtually unaltered in other muscles
(VM and BF) in the CON and HIGH conditions. As proposed by \citet{Wilson_2019}, a
shortening Tc and a decrement in Dm parameters can be interpreted as a
sign of neuromuscular potentiation. Since potentiation was only observed
in RF after the LOW condition, it could be demonstrating that the effect
of tissue flossing is precisely localized to the wrapped body area and
has a negligible effect on the neuromuscular parameters of muscles
distal from the wrapped area.
Moreover, in the present study, the ASLR test remained unaltered,
regardless of the wrapping pressure. Even though there were no
statistically significant differences, a drop in ASLR 30 minutes after
the CON condition compared to LOW is very likely associated with themedium effect recorded. One of the most significant practical
implications arising from previous tissue flossing studies where floss
band had been applied around the ankle joint, was the enhancement in
ankle joint range of motion (ROM) while maintaining, or even increasing,
athletic
performance \cite{Driller_2017,Driller_2017a}.
In contrast, the findings of the present study suggest that when floss
band is wrapped around the upper thigh, it has no significant effect on
the adjacent joint range of motion (ASLR test remained unchanged). It
could suggest that hypoxia and reperfusion may not be the only mechanism
inducing ROM improvement after tissue flossing. These findings suggest
that there are different mechanisms causing the observed changes in
neuromuscular parameters. We can speculate that one possible mechanism
could be the stimulation of pressure-sensitive mechanoreceptors in the
tissue directly under the wrapped part of the body. The fact that
mechano-sensory receptors are more abundant in ankle joint tissue
compared to muscles and
tendons \cite{Taylor_2009} may explain why ROM improved in ankle wrapping studies but no ASLR
improvement was observed in the present study.
The present study might have some limitations. First: although the
pressure was individualized according to the literature and controlled
using a pressure sensor, there was no insight into the actual blood-flow
occlusion created in the affected leg. Furthermore, it was difficult to
consistently and accurately apply the floss band in the HIGH condition,
resulting in higher deviation from the target pressure. Second: it is
difficult to explain why knee flexors were not affected by the floss
band since they were partially wrapped as well. Although the floss bands
were expertly applied for consistent banding on the front and back of
the thigh, pressure sensors were only placed frontally therefore
pressure, and thus vascular occlusion, for BF may have been different.