Developing flexibility by improving both active and passive range of motion (ROM) is crucial in many sporting activities. Static, ballistic and dynamic stretching as well as proprioceptive neuromuscular facilitation are relevant methods to increase ROM (Behm and Chaouachi, 2011; Behm et al., 2016; Kay and Blazevich, 2012; Page, 2012). Static stretching is one of the most widely used method, due to its simplicity and low risks of tissue trauma (Alter, 1988; Roberts and Wilson, 1999; Sady et al., 1982). Alternative techniques have been recently investigated. Among them, foam rolling (FR) through foam roller or roller massager became a very popular method to improve functional mobility and ROM (for an extensive review, see Cheatham et al., 2015). Likewise, variable resistance training using elastic bands may contribute to assist stretching techniques and improve flexibility by facilitating joint distraction and decoaptation, hence allowing the joint surfaces to gap away from one another (Page and Ellenbecker, 2003; Rosengart, 2013).
FR is believed to positively affect fibrous adhesions in the fascia, and to restore muscles, tendons, ligaments, fascia, and soft-tissue extensibility. Although he did not directly study the effect of FR, Barnes (1977) provided a theoretical framework for the possibility of affecting fibrous adhesions, while Schleip (2003) reported that supra-physiological forces are needed to break-up fascial adhesions. Cheatham et al. (2015) extensively described the impact of FR on the properties of the fascia (e.g., alteration of the viscoelastic and thixotropic properties), and how it contributed to increase the intramuscular temperature and blood flow. FR also results in reduced arterial stiffness and improved vascular endothelial function (Okamoto et al. 2014). The vast majority of experimental research revealed that FR may offer different kinds of benefits in terms of motor performance, flexibility and recovery (for reviews, see (Beardsley and Skarabot, 2015; Cheatham et al., 2015; Schroeder and Best, 2015; Kalichman and Ben David, 2017; Mauntel and Padua, 2014). Two studies even demonstrated that rolling the contralateral limb contributed to significant decreases in pain in the affected limb (Aboodarda et al., 2015; Cavanaugh et al., 2016). More generally, prophylactic effects of FR have been reported, due to its effect on the connective tissue and local blood flow. FR was found to attenuate the decrease in muscle performance, and both reduce and delay muscle soreness (Aboodarda et al., 2015; Cheatham et al., 2015; Jay et al. 2014; MacDonald et al., 2014; Pearcey et al., 2015; Schroeder and Best, 2015; Romero-Moraleda et al., 2017). Experimental studies did not report, in contrast, clear effects of FR when performed prior to motor performance. While it may not be harmful for subsequent performance, FR was not found to positively impact performance gains such as strength, power, jump, or shuttle run tasks (Fama and Bueti, 2011; Halperin et al., 2014; Healey et al., 2014; Jones et al. 2015; Mikesky et al., 2002; Peacock et al. 2015, but see the recent study by Romero-Moraleda et al., 2017 for positive effects of FR on strength). Interestingly, and despite some conflicting results (Couture et al., 2015), FR has been found to substantially increase ROM of the hip (Behara and Jacobson, 2015; Bushell et al., 2015; De Souza et al., 2017; Mohr et al., 2014; Monteiro et al. 2017), knee (Button and Behm, 2014; Bradbury-Squires et al., 2015; MacDonald et al., 2013, 2014; MacDonald et al., 2013; 2014; Vigotsky et al., 2015), and ankle (De Souza et al., 2017; Halperin et al., 2014; Skarabot et al., 2015), without hampering muscle performance (see Halperin et al., 2014). Similar findings were reported for the sit and reach test (Sullivan et al., 2013; Pearcey et al., 2015). As both FR and stretching are likely to improve ROM, combining these two types of practice may result in greater performance gains (MacDonald et al., 2014; Roylance et al., 2013; Skarabot et al., 2015). Altogether, these data support the benefits of FR for enhancing joint ROM (Cheatham et al., 2015). While some studies compared the effectiveness of different types of roller (during either pre or post-exercise), as well as the nature and the duration of the massage pressure (Cheatham et al., 2015; Curran et al. 2008; Debruyne et al., 2017; De Souza et al., 2017; Monteiro et al., 2017), the effects of a longer FR intervention targeting several muscles on ROM, throughout several training sessions, has received little attention. Junker and Stoggl (2015) investigated the effectiveness of a 4-week training with the foam roll method on hamstring flexibility. They provided evidence that FR is effective to improve range of motion, such beneficial effects being comparable with those provided by the well-known contract-relax proprioceptive neuromuscular facilitation stretching method. There is a lack of unanimity in the literature, however, as a recent study by Hodgson et al. (2018) did not show improved flexibility after 4 weeks of rolling. Spurred by the positive findings and due to the conflict in the scientific literature, further experimental data looking at the long-term effects of FR are required to confirm the benefits of FR on the thixotropic properties of the muscle (Axelson and Hagbarth, 2001), with long-term effects which may arise from decreasing tissue adhesion (McHugh et al., 2012), and improving fascia elasticity (Wilke et al., 2016).
Joint distraction with elastic bands training (EBT) is another emerging and cost-effective component of strength and conditioning programs. Traditionally, this method has been used for strengthening muscle and improving power and velocity (Jakobsen et al., 2013; Joy et al., 2016; Jakubiak and Saunders, 2008; Rhea et al., 2009; Smith et al., 2011; Treiber et al., 1998). As well, EBT has been found to enhance jumping and sprinting performance, hence providing an alternative training method as a part of plyometric programs (Argus et al., 2011; Janot et al., 2013) or during warm-up (Wyland et al., 2015). Soria-Gila et al. (2015) reported that EBT might even result in greater strength gains than conventional weight training, while Park et al. (2015) illustrated its benefits to improve endurance, balance, agility and quality of life in elderly persons (see also Oesen et al., 2015, but Vinstrup et al., 2016, for challenging results). Another promising effect of EBT is that it may facilitate the effectiveness of motor recovery by maximizing strength gains in injured athletes while being less boring than conventional stretching, and therefore more likely to be adhered to (Lorentz, 2014). Surprisingly, very few studies investigated the effect of EBT on flexibility, although its properties make it ideal for providing load during stretching exercises (Carrio, 2012; Donatelli and McMahon, 1997; Page and Ellenbecker, 2003). Practically, joint distraction exercises might be incorporated during stretching routines in order to create more space in the joint complex (Rosengart, 2013). During joint distraction, elastic bands act as wedges to separate the joint surfaces from one another (Rosengart, 2013), hence presumably providing more space for synovial fluid to fill the joint and reduce the amount of friction (Bourneton, 1981; Le Roux and Dupas, 1995). Another advantage is that the resistance can be individually adjusted to the tolerance of the person. Joint distraction using elastic bands might thus be used not only to assist static stretching, but also active and dynamic stretching. Including elastic band training in a specific experimental protocol designed to improve flexibility appeared an original approach which has been quite neglected in the literature, with the advantage of providing an individualized form of practice with a constant traction. In addition, due to its self-adjusting nature, elastic band exercises allow participants to apply a closed-loop motor control to promote and reinforce joint distraction before performing the stretching routine.
The present study included two experiments designed to respectively investigate the effectiveness of FR and EBT on range of motion in national rugby players. In contrast to the majority of experimental studies looking at the immediate and short term effects on functional performance, we tested the effect of a 7-week training program on the performance of several stretching exercises. We hypothesized that both FR and EBT would contribute to improve joint flexibility and facilitate stretching processes.
Thirty professional national-level male rugby players (M = 18.85 years, SD = 1.10 years) voluntarily participated in Experiment 1. Twenty-three professional national-level male rugby players (M = 17.22 years, SD = 0.60 years) were recruited for Experiment 2, which was performed 1 month after Experiment 1. None of the participants were enrolled in both experiments, so that all players were selected from different Rugby teams. Anthropometric characteristics of the participants are displayed in Table 1. Players provided written and informed consent in agreement with the terms of the Declaration of Helsinki (1982). Prior ethical approval was granted by the Research Ethics Committee of the Center of Research and Innovation in Sport (University Claude Bernard Lyon 1). Any foam rolling training was suspended for 72 h prior to each experiment, and participants were requested to not practice outside of the supervised sessions until completion of the experimental procedure. Participants were not enrolled if they had suffered from any traumatic injury requiring a healing rest-period during the month preceding the experiments. None of the participants was injured during the experimental interventions.
The test-retest study spanned over a 7-week period and consisted in a pre-test (Week 0), a FR...