Boxing is a combat sport that requires the unique combination of well-developed hand and foot speed, footwork, evasion skills, muscular strength and power as well as a high aerobic capacity (Zazryn et al., 2006). Boxing matches are won either by the participants who score more points (i.e. landing legal punches) or when the opponent is unable to continue to fight (Zazryn et al., 2006). Previous studies have demonstrated that boxers with great physiological capacities such as a high individual anaerobic threshold and hand grip strength typically have a better competitive ranking (Guidetti et al., 2002). However, these physiological aspects are not the only determinants of optimal performance in boxing. In fact, such performance depends on a combination of technical skills, psychological and physiological aspects (Guidetti et al., 2002) and this complexity makes it difficult to quantify the training load in boxing.
Although each boxing training session will vary in content according to the training objectives, it generally consists of activities such as warm-up, rope skipping, skill development boxing exercises, bag punching drills and sparring with partners. Due to the combative nature of boxing, it is difficult to assess exercise intensity during these sessions using traditional objective methods such as heart rate monitors or other microtechnology devices (i.e. GPS, accelerometers etc.), as these devices may interfere with training, especially during sparring. In fact, a common problem for coaches and scientists working with boxing is the difficulty in quantifying training load.
Accurate measurements of training load are essential in a well-controlled training plan (Banister et al., 1975). At present, no studies have investigated the most appropriate methods for quantifying training load in boxing. However, the session rating of perceived exertion (session-RPE) method (Foster et al., 2001) for quantifying training load has shown to be valid for many sports, including soccer (Alexiou and Coutts, 2008; Impellizzeri et al., 2004), Australian football (Scott et al., 2013), taekwondo (Haddad et al., 2011), cycling (Foster et al., 2001), swimming (Wallace et al., 2009) and resistance training (Day et al., 2004; Singh et al., 2007). This method uses a modified version of Borg's CR-10 scale (Borg et al., 1985) of perceived exertion as a measure of intensity to quantify the training doses. Athletes provide a session-RPE measure 30 minutes after bout by rating their perception of effort for an entire session, and this rating can be multiplied by the training session duration in minutes to provide session RPE method (internal training load). The rationale behind the 30 minutes period before the session-RPE collection is that either easy or hard exercise periods near the termination of the exercise sessions may have a 'recency' effect on global RPE measures if completed at the end of the session (Foster et al., 2001). Hornsby and colleagues (2013) indicated, in a recent publication, that session-RPE is not linked to terminal acute RPE. Presently, it is unknown if reporting session-RPE earlier (10 minutes after completing each training session) could alter the training load score. Indeed, the 30 minutes time delay required to assess session-RPE is generally considered a practical limitation of this approach, as it increases time demand on athletes.
Thus, the first aim of the present study was to verify if session-RPE estimations obtained 10 minutes after boxing training sessions of different intensities differed from session-RPE taken after 30 minutes. We hypothesized that a reduced period between the training session and providing the session-RPE measurement would not affect with the result. The second aim was to determine whether session-RPE measurements could be used to identify different intensity training sessions in boxing.
Eight male Olympic boxing athletes (age = 18.8 [+ or -] 1.8 years; height = 1.71 [+ or -] 0.09 m; body mass=66.7 [+ or -] 16.5 kg) from the same boxing team volunteered to participate in this study. No participants reported any history of injury within one year before recruitment. All athletes were tested during the preparation phase (i.e. mesocycle) of the training calendar. Each participant had at least four years of boxing experience, and typically performed three boxing-specific training bouts (2 hours) each week. All participants were informed about the aims and risks of participating in the present study and signed an informed consent document before engaging in the study. The study was approved by the Ethics Committee of the School of Physical Education of Jundiai (ESEF).
Initially, a pilot study was conducted to evaluate the exercise intensities of boxing sessions (i.e. easy, moderate and hard) according to the session-RPE scale. This pilot study revealed differences in session-RPE values among the three different groups, and demonstrated that different cadences of boxing movements could be used to modulate session-RPE in boxing. Prior to the pilot study, all athletes were familiarized with the RPE scale (Borg's CR10-Scale) and had completed over 20 regular training sessions using session-RPE. According to the methods of Foster et al. (2001), 30 minutes after each session athletes estimated RPE according to the session-RPE method. In this study, the Portuguese translation of the RPE method modified by Foster et al., (2001) was used.
This study used a randomized, matched pairs crossover research design. That is, pairs performed all the bouts of different intensities for 45 minutes each and post exercise session-RPE was collected after 10 minutes or 30 minutes. Following the pilot study, participants were divided into four pairs (i.e. training partners) according to their boxing ability. Each pair was randomly assigned to complete an easy, moderate or hard training session, which was closely supervised by one of the investigators. Each boxing session was matched for training content...