Introduction

Tissue flossing has become an increasingly popular technique among physiotherapists and strength and conditioning specialists, mostly used as a rehabilitation or performance enhancing tool\cite{Driller_2017}. The method consists of tightly wrapping part of a limb or a joint with a 1 to 2 mm thick elastic band, causing partial vascular occlusion of the blood flow distal to the wrapped area.
Despite the popularity of this method, the acute effects of tissue flossing on neuromuscular functions are still poorly understood; moreover, at the time of writing this paper, there was limited scientific evidence underlying the efficiency of this method. The majority of published studies have investigated the effects of tissue flossing applied to the ankle joint, which resulted in increased ankle range of motion (ROM) \cite{Vogrin_2020}, increased jump and sprinting ability \cite{Driller_2017,Driller_2017a}. On the other hand, only two peer-reviewed studies have investigated the effects of tissue flossing around a limb (thigh and upper-arm). Both the aforementioned studies investigated the effects of tissue flossing as a treatment for delayed onset of muscle soreness (DOMS), leading to conflicting results: in the study conducted by \citet{Prill_2019}, tissue flossing resulted in lower effectiveness than other gold standard methods to alleviate the effects of DOMS. However, the authors advocated that tissue flossing is a valid, practical and cost-effective method. In contrast, \citet{Gorny_2018} applied three sets of two-minute tissue flossing to the upper-thigh region after an exercise-induced muscle damaging protocol, finding that tissue flossing has no effects on DOMS reduction.
Although there are no available studies directly comparing tissue flossing with ischemic preconditioning/blood flow restriction (BFR) training, there are similarities between the methods \cite{Driller_2017}. Similar to tissue flossing, BFR training consists of complete occlusion of venous and partial occlusion of arterial blood flow to a limb using an elastic wrap \cite{Loenneke_2009} or a specialized inflatable cuff \cite{Takano_2005}. There is strong evidence in the literature showing the positive effects of low-load BFR training on chronic neuro-muscular adaptations \cite{Fahs_2014,Loenneke_2014,Scott_2014,Takarada2002}. On the other hand, there is evidence in the literature that single low-load BFR training sessions acutely decrease neuromuscular performance \cite{COOK_2013,HUSMANN_2018,Sieljacks_2015}, although \citet{Girard_2019} failed to find such differences during a multi-set resistance exercise leading to volitional failure in diverse conditions of systemic hypoxia, BFR, or normoxia. Divergence in the literature arises from differences in protocols, in particular, in the use of different restrictive pressures. Some authors \cite{Scott_2014a} have proposed cuff pressure individualization to achieve more reliable results. Indeed, \citet{Loenneke_2015} and \citet{Fatela_2016} demonstrated that different relative blood flow occlusions result in different neuromuscular impairments.
To our knowledge, there are no studies in the literature investigating the effect of tissue flossing around a limb on neuromuscular performance. Moreover, a fixed apriori-defined high wrapping pressure (approx. >180 mmHg) was used in the majority of previous tissue flossing studies \cite{Driller_2017,Vogrin_2020,Driller_2017a,Mills_2020}. Therefore, the aim of this study was to investigate the acute effects of tissue flossing applied over the upper-thigh region by using different degrees of wrapping pressure on Active straight leg raise test, maximum voluntary contraction, and the contractile characteristics of knee extensors and flexors assessed using tensiomyography.

Methods

Study design

The present study followed a cross-over repeated measures design. Each subject was exposed to three similar intervention protocols, one per visit. At each visit, following warm-up and pretest assessments, the upper-thigh of the dominant leg was wrapped using a rubber elastic band (floss band), with subjects being instructed to perform active knee extension and flexion movements. The pressure used to wrap the band was individualized to each subjects’ thigh circumference and was different on each visit according to the selected protocol (CON, LOW, HIGH). During each visit, comprising pre (PRE), immediately after (POST) and 30 minutes after (POST30) applying the floss band, participants performed several lower-leg assessments in the following order: i) Active straight leg raise test (ASLR); ii) TMG of the rectus femoris (RF), vastus medialis (VM) and biceps femoris (BF) muscles; iii) maximum voluntary contractions of knee extensors and flexors - MVC (see Figure \ref{975321}). There were at least 48-hours of delay between consecutive visits to avoid between-session influences.