Rock climbing has increased its popularity in recent decades gaining the attraction of both athletes and researchers (Heyman et al., 2009; MacLeod et al., 2007; Magiera et al., 2013; Sheel, 2004; Sherk et al., 2011; Watts, 2004). This sport offers a great variety of disciplines, each of them with specific features that provoke different physiological demands and responses (Draper et al., 2006b).
In this study we will focus on sport indoor rock climbing, which consists of ascending a wall helped by artificial structures with hands and feet being the climber permanently protected from falling thanks to a succession of pre-installed attachment points for the rope along the climbing route. In this discipline ascents last between one and two minutes (Draper et al., 2006b) and blood lactate concentration can be considered as an indicator of fatigue (Bertuzzi et al., 2007; Billat et al., 1995; Booth et al., 1999; Draper et al., 2006b; Espana-Romero et al., 2009; Mermier et al., 2000; Sheel, 2003; 2004), which shows its similarity with other short term high intensity efforts where glycolysis provides the main energy source (Draper et al., 2006b).
Forearm muscles strength has also been described as a good indicator of performance (Bertuzzi et al., 2011; Magiera et al., 2013; Deyhle et al., 2015; Espana-Romero et al., 2009; Gajewski et al., 2009; MacLeod et al., 2007; Mermier et al., 2000; Watts et al., 2000) as its fatigue can result in a decrement of climbing performance.
Watts et al (2000) indicated the necessity of studying the effect of different recovery strategies between climbing ascents due to the multiple routes or efforts on a specific route that climbers are required to perform in competitions, as well as repeated climbing efforts that they carry out during training sessions.
Numerous studies have found improved lactate removal and/or performance with active rather than with passive recovery in different types of exercise (Baldari et al., 2005; Connolly et al., 2003; Corder et al., 2000; Heyman et al., 2009; Martin et al., 1998; Menzies et al., 2010; Monedero and Donne, 2000; Spierer et al., 2004; Wells, 2015; White and Mika et al., 2007). Active recovery has been shown to enhance lactic acid clearance from type II skeletal muscle fibers through facilitating its oxidation by adjacent type I fibers (Baldari et al., 2005). Moreover, other studies (Fujita et al., 2009; McLoughlin et al., 1991) have shown that activating previously inactive muscles can also improve blood lactate removal. Therefore, the type of active recovery carried out can be important since the quantity and type of muscle mass activated may influence the increment in blood flow to different parts of the organism, facilitating metabolites clearance and removal and consequently improving performance.
Previous research has demonstrated that walking and cycling are beneficial modes of active recovery in climbing (Draper et al., 2006b; Heyman et al., 2009; Watts et al., 2000). In the named experiments the exercises chosen to recover from climbing did activate great muscle groups (lower limbs) but not the main producers of lactate (upper limbs, specially forearm muscles), which could accelerate the rate of lactate clearance by adjacent type I fibers in the previously working muscles as well as lactate removal by hitherto-inactive muscles or other organs such as the liver (Gladden, 2000; 2004).
The aim of this study was to determine if activation during active recovery of both great muscle mass as well as the principal lactate producing muscles can improve recovery in comparison with activating just great muscle mass. For this purpose, walking -which activates the muscles of the lower limbs--has been compared with easy climbing -which in addition to the lower limbs muscles activates the forearm muscles, which are the main producers of lactate and fatigue in climbing (Watts et al,. 2000; 2008)-. Both central (Rate of perceived exertion) and peripheral (Blood lactate and heart rate) fatigue indicator have been analyzed, as well as their consequences in performance (meters climbed and handgrip force).
Fourteen male recreational climbers (descriptive data presented in Table 1) with an intermediate-advanced level (Draper et al., 2011) from the climbing school at University of Alcala volunteered to take part in this study. The criteria for acceptance as a subject included climbing a minimum of 4 hours/week, a climbing experience greater than 2 years and red point climbing ability of minimum 6c, as well as refraining from doing intense exercise the day prior to testing sessions. For the duration of the study subjects were instructed to maintain normal dietary patterns and refrain from using any ergogenic aids or stimulants such as caffeine.
Ethical approval was obtained for the study in accordance with the University of Alcala Ethics Committee regulations and all participants completed an informed consent form after having the procedures verbally explained. Data of all subjects were anonymized. Participants had been familiarized with the climbing route having trained on it on a session that took place one week before the first testing session. This familiarization session consisted of five ascents to the climbing route at a self-regulated speed so at to memorize the necessary movements.
For the assessment of influence of the recovery mode, two different active recovery methods were evaluated: Walking recovery (WR) and easy climbing recovery in a 12meter route graded 4c in the French scale (CR). Both recovery methods were carried out at a self-regulated exercise intensity, as previous studies have indicated that this allows for improved lactate removal (Belcastro and Bonen, 1975; Menzies et al., 2010) as well as an optimal relationship in rock climbing between isometric time (workless and costly) and fatigue due to increased speed and frequency of muscle contraction (Rosponi et al., 2012). All participants completed both WR and CR recovery conditions using a randomly assigned two-way crossover design. There was a separation of seven days between each condition.
Prior to the climbing protocol, participants followed a ten minute warm-up which consisted of light jogging, articular mobility exercises and one light ascent of the testing route. The climbing protocol was identical for both conditions. Subjects performed three repetitions of two minutes maximal climbing efforts with two minutes of active recovery between them. During these recovery periods WR condition participants walked and CR condition participants climbed a route graded 4c at a subjectively chosen intensity, having been verbally told to perform the recovery exercise at the speed they considered optimal to recover from the previous effort. So as to avoid a competitive attitude between participants during recoveries, distance covered during this phase was not recorded. Active recovery was carried out for 1.5 minutes and the next 30 seconds were left as passive recovery to measure handgrip force and blood lactate (Figure 1) as well as to maintain the ecological validity of the climbing context, as climbers usually need some time before ascending to prepare themselves mentally for the next climbing trial and re-chalk their fingers (Draper et al., 2006b). The duration of the recovery phase was chosen to last 2 minutes so as to imitate a possible situation during training sessions, where climbers usually alternate with their belayers to ascend the routes and therefore rest while the other person is climbing.
After the last 2 minute effort...