In team handball, throwing performance is determined by both velocity and accuracy (Wagner et al., 2008). The combination of these two factors gives defenders and/or goalkeepers less time to parry the shot, thus increasing the likelihood of scoring (van Muijen et al., 1991). Throwing performance is the result of sequential muscle activation, torque generation, energy transfer, and a proximal to distal increase of joint angular velocities in the kinetic chain that starts in the lower extremities and progresses through the trunk into the upper extremities (Bartlett, 2000; Fradet et al., 2004; Herring and Chapman, 1992; Joris et al., 1985; Roach et al., 2013; van den Tillaar and Ettema, 2004; 2007; 2009b; Wagner et al., 2011; 2012; 2014). This sequential behaviour requires joint mobility for both angular acceleration and deceleration throughout the kinetic chain. In their study Roach and Lieberman reported that limiting proximal kinetic chain segmental mobility by bracing decreased joint power generation throughout the kinetic chain, angular velocities, elastic storage of energy at the shoulder, and throwing velocity (Roach and Lieberman, 2014). Furthermore, kinetic chain analyses of handball throwing found correlations between throwing velocity and maximum joint positions obtained during the cocking and acceleration phase (van den Tillaar and Ettema, 2007; Wagner et al., 2011).
Since full kinetic chain analysis of throwing performance is an impractical field method, joint mobility is commonly quantified using traditional goniometric measurements of range of motion (ROM). However, only few studies explored the influence of ROM measurements on throwing performance, and non-significant findings have been reported (Schwesig et al., 2016; van den Tillaar, 2016). Furthermore, ROM measurements have an uncertain capacity to predict injuries (Andersson et al., 2018; Clarsen et al., 2014). These findings might be due to some inherent limitations of the traditional measurements. Firstly, ROM measurements might not be representative of the actual maximum joint movements attained during the throw (van den Tillaar, 2016). Secondly, goniometric measures only provide information about uniplanar and unidirectional movements of specific joints, and do not provide information about their role in the kinetic chain. Thirdly, in the current literature assessing throwing performance, goniometric measures are only applied to upper extremity joint movements, even if maximum trunk and pelvic rotations have been reported to also be important determinants (Wagner et al., 2011). Finally, passive goniometric tests have low neuromuscular demands. In fact, to the knowledge of the authors no studies so far explored the influence of dynamic postural control on team handball throwing performance. The lack of measurements that target kinetic chain assessment of both mobility and dynamic postural control are in contrast to current practice in the female Norwegian national team, where testing and training that integrate lower extremity, trunk and shoulder movements are used for both mobility and dynamic postural control purposes. Considering that this is the most successful female handball team in the past two decades (Olympic games, World Championships and European Championships several gold, silver and bronze medals), it is interesting to observe that such assessments are lacking in the literature.
Considering the aforementioned shortcomings, a study into the influence of mobility on throwing performance should include assessment of the full kinetic chain and impose greater neuromuscular demands. Thus, tests of functional mobility--i.e. the combination of range of motion (ROM) of multiple joints in ecological movements might be an appropriate assessment strategy. The hand reach star excursion balance test (HSEBT) appears to be an appropriate test since the joint movements elicited by the different sub-tests (Eriksrud et al., 2018) are similar to those associated with overhead handball throwing (van den Tillaar and Ettema, 2007; Wagner et al., 2011). Other tests such as the star excursion balance tests (SEBT) (Gribble et al., 2012; Kang et al., 2015), upper quarter Y-balance test (UQYBT) (Gorman et al., 2012) and functional movement screen (FMS) (Butler et al., 2010; Cook et al., 2006) do not have this capacity.
Specifically, the HSEBT posterior overhead unilateral hand reach measurements quantify the ability to position the hand in space, which elicit hip, trunk and shoulder joint movements (Eriksrud et al., 2018) similar to those observed in the late cocking and acceleration phases of overhead throwing (van den Tillaar and Ettema, 2007; Wagner et al., 2011). Furthermore, the unilateral anterior diagonal hand reaches to floor level elicit combinations of hip, trunk and shoulder joint movements (Eriksrud et al., 2018) similar to those observed in the follow-through phase (van den Tillaar and Ettema, 2007; Wagner et al., 2011). In addition, the rotational reaches target transverse plane joint movements (Eriksrud et al., 2018) associated with the different phases of the throw (van den Tillaar and Ettema, 2007; Wagner et al., 2011).
Therefore, the purpose of this study was to determine the influence of functional mobility and dynamic postural control assessed through specific HSEBT reaches on team handball throwing performance. We hypothesized that specific HSEBT measures correlate with throwing accuracy or throwing velocity.
Thirteen Norwegian, international level, female handball players volunteered for the study, with eleven completing the entire protocol (age: 21.7 [+ or -] 1.8 years; weight: 71.3 [+ or -] 9.6 kg; height: 1.75 [+ or -] 0.07 m; wingspan: 1.74 [+ or -] 0.09 m). Debut in the elite division in Norway was 3.5+1.9 years prior to participation in the study, and at the time of the study two players were on the national team while four different players participated in European club competitions. Exclusion criteria were musculoskeletal or neurological dysfunction or injury in the past six months, inability to participate in normal handball and throwing activities, and pain or discomfort reported during testing. All tests were done in the afternoon and participants were instructed to eat and hydrate as they would do for a regular practice. The committee for medical and health research ethics in Norway (2014/2230) and the Norwegian Centre for Research Data (40934) had reviewed and approved the study. Measurements were carried out according to the principles described in the Declaration of Helsinki. All subjects were given written and verbal information about the experimental risks associated with the study and signed an informed consent form prior to participation. Testing was done mid to late season.
This was a descriptive and cross-sectional cohort study for comparison of HSEBT reaches with overhead throwing performance (ball velocity and accuracy). Specifically, HSEBT reaches that represent joint movements associated with the different phases of the overhead handball throw, cocking, acceleration and follow-through, were selected. The unilateral posterior overhead reaches (L135 and R135) were tested since hip, trunk and upper extremity joint movements and positions assumed in these reaches (Eriksrud et al., 2018) are similar to those observed in the cocking and acceleration phase in the same joints (van den Tillaar and Ettema, 2007; Wagner et al., 2011). Similarly, the unilateral anterior diagonal reaches to floor level (L45 and R45) were tested since hip, trunk and upper extremity joint movements and positions assumed in these reaches (Eriksrud et al., 2018) are similar to those observed in the follow-through phase in the same joints (van den Tillaar and Ettema, 2007; Wagner et al., 2011). Furthermore, Left (LROT) and right (RROT) rotational reaches were done to target the hip and trunk rotations associated with the three phases of the throw (van den Tillaar and Ettema, 2007; Wagner et al., 2011).
Anthropometric measurements and limb dominance
Prior to testing, body height and weight were obtained using a Seca model 217 stadiometer and a Seca flat scale (Seca GmbH. & Co. Hamburg, Germany). A standard tape measure was used to measure wingspan (tip of middle finger to middle finger with shoulder abducted to 90 degrees in standing), arm length (acromion to tip of middle finger with shoulder abducted to 90 degrees in standing) and leg length (greater trochanter to floor in standing). The dominant hand was defined as the throwing hand, while the dominant foot was defined as the pivot foot in the 8-meter throw with run-up.
All subjects performed a 15-minute standardized warm-up. The general warm-up (10 minutes) consisted of jogging, different shuffle runs, skipping and dynamic stretching focusing on full body movements in all three planes of motion. The handball-specific part (5 minutes) consisted of throwing at a large target (wall) with a gradual increase in velocity with the last 2-3 throws at maximum throwing velocity.
A throwing target was indicated on a high-jump mat (2 m x 3 m) placed vertically in front of a handball goal in order to protect lab equipment. Based on different protocols previously used in handball throwing studies (van den Tillaar and Ettema, 2003; Wagner et al., 2014) sports...