More than the shoulder? Kinematics of the jump throw and factors influencing shoulder problems in handball

Abstract

Aims: Shoulder problems are common in handball and known risk factors include decreased shoulder rotational strength, limited shoulder rotational mobility, and sudden increases in training and competition load. The throwing motion is a large movement, and previous research has linked proximal segments´ force production to throwing velocity. Nevertheless, the influence of lower body strength and trunk rotation power (TRP) on shoulder problems in handball players has not been investigated prospectively. Similarly, the association between internal shoulder load (subjective perception of load) vs. external shoulder load (e.g. number of throws in a match) measurements and shoulder problems among handball players is unknown. Despite the jump throw being the most common throwing technique in handball, very few motion analyses of it have been conducted. Moreover, the extent to which proximal segments’ kinematics influence more distal segments, such as the shoulder, is unknown, as are possible kinematic differences between different positions. The aims of this thesis were to examine the association between pre-season strength and power in the lower body and trunk, and shoulder problems among handball players, to perform a 3D motion analysis of the jump throw and, to investigate whether internal or external shoulder load measurements were more consistently associated with shoulder problems. Increased knowledge of this topic might influence injury prevention via better load management, either by ensuring adequate pre-season strength and power or by regulating training/competition shoulder load.Methods: This thesis is based on results from three research papers. Paper I included 42 male handball players. Pre-season measurements of peak lower body strength, peak trunk rotation power (TRP), and peak external and internal rotation strength in the throwing shoulder were conducted before the 2022–2023 season. Participants were followed throughout a whole regular season (31 weeks), where they answered a weekly questionnaire specially designed to document the prevalence and severity of overuse problems, and an additional question regarding participation-related shoulder load (PSL – subjective experience of shoulder load (internal load)) during the previous week. Paper II involved 31 female handball players. The same pre-season protocol as used in paper I was conducted before the 2023–2024 season and participants answered the same questionnaire throughout the season (29 weeks). Performance data, including the total number of shots per player in all league matches were collected from HBstatz (official statistical provider for the Icelandic Handball Federation) and defined as external shoulder load. For paper I and II, the association between pre-season strength and power and the prevalence and severity of shoulder problems was assessed with the Spearman´s rho correlation coefficient. The influence of pre-season strength and power on the association between internal and external shoulder load, and the severity of shoulder problems was examined with a mixed model ANOVA. Paper III involved a 3D motion analysis of 41 male top-division players performing a jump throw, conducted before the 2022–2023 season. The correlation between proximal and distal segments´ kinematics was assessed and differences in jump throw kinematics between playing positions were analysed with an independent t-test. The explanatory strength of proximal segments´ kinematics on the variance in shoulder internal rotation (IR) angular velocity was assessed by using a stepwise regression model. Results: The results from paper I (male players) showed a negative correlation between pre-season ER strength and the prevalence of shoulder problems (rs=-0.34, p=0.029). A main effect was observed showing a positive relationship between PSL and the severity of shoulder problems (p<0.001). A significant interaction was observed between PSL and pre-season TRP in terms of their influence on the severity of shoulder problems, as males with pre-season TRP one standard deviation (SD) below the group´s mean had a stronger association between the severity score and PSL. The findings from paper II (female players) showed a positive correlation between peak lower body strength (rs=0.40, p=0.03) and peak ER shoulder strength (rs=0.38, p=0.04), and the prevalence of substantial shoulder problems. A main effect was again observed for PSL, with higher PSL associated with higher severity score (p<0.001). However, a negative association was found between the external shoulder load and the severity of shoulder problems (p=0.04). A significant interaction was observed between PSL and peak lower body strength, TRP, and ER shoulder strength in terms of their influence on the severity of shoulder problems. Female players with pre-season strength and power one SD above the group´s mean showed a stronger association between the severity score and PSL. Paper III showed that hip and pelvis kinematics explained 44% of the variance in shoulder IR angular velocity. Significant differences were found between positions with center/back players displaying higher angular velocities in all measured segments, except trunk rotation, and greater range of motion excursion in the hips, pelvis, and trunk compared to wing/pivot players. Conclusions: The findings suggest that low pre-season TRP in male players may make the throwing shoulder more vulnerable for an increase in load. Pre-season training should therefore emphasize TRP training for male players. However, the results highlight the complex interaction between multiple risk factors for shoulder problems in female players and suggest that PSL (internal load) is more consistently associated with shoulder problems in handball, compared to external load. The results also underscore the role of proximal segments´ kinematics in terms of an efficient jump throw performance, and that different on-field demands likely influence kinematic differences between central/back vs wing/pivot players. It is therefore important to tailor strength training accordingly to each player’s on-field demands.

Markmið: Axlarmeiðsli eru algeng á meðal handboltaiðkenda og á meðal þekktra áhættuþátta eru skortur á styrk og hreyfigetu í öxl og skyndileg aukning í æfinga- og keppnisálagi. Kasthreyfingin er stór, framkvæmd með öllum líkamanum og rannsóknir hafa sýnt að kraftmyndun í neðri útlimum og bol tengist kasthraða. Áhrif styrks og afls í neðri útlimum og bol á þróun axlarmeiðsla í handbolta hafa hins vegar ekki verið könnuð í framskyggnum rannsóknum. Áhrif innra álags á öxl (sjálfsmat á álagi) samanborið við ytra álag (metið með t.d. fjölda skota í leik) á þróun meiðsla í kastöxl yfir keppnistímabil hafa ekki verið könnuð á meðal handboltaiðkenda. Þrátt fyrir að uppstökk sé ein algengasta kasttæknin í handbolta hafa fáar rannsóknir greint hana með þrívíddartækni. Áhrif hreyfinga í neðri útlimum og bol á kastöxlina eru því lítið þekkt sem og áhrif leikstöðu. Markmið þessa doktorsverkefnis var því í megindráttum tvíþætt; að kanna tengsl á milli grunnstyrks og afls í neðri útlimum og bol og axlarmeiðsla yfir heilt handboltatímabil og að greina hreyfimynstur í uppstökkskasti með þrívíddarhreyfigreiningu. Einnig var innra og ytra álag á kastöxl áætlað yfir tímabilið til að meta hvor mæling hefði sterkari tengsl við axlarmeiðsli. Aukin þekking á sviðinu mun gefa sterkari forsendur fyrir meiðslaforvarnir í gegnum álagsstýringu, hvort sem er í gegnum grunnstyrk og kasttækni eða með temprun á keppnis- og/eða æfingaálagi. Aðferðir: Framkvæmd rannsóknanna sem þessi ritgerð byggir á var þrískipt. Þátttakendur í fyrsta hlutanum voru 42 leikmenn úr efstu deild karla í handbolta. Mælingar á hámarksstyrk í neðri útlimum, hámarkssnúningsafli í bol og hámarkssnúningsstyrk í kastöxl voru framkvæmdar fyrir keppnistímabilið 2022-2023. Þátttakendum var í kjölfarið fylgt eftir í gegnum heilt keppnistímabil (31 vika) þar sem þeir svöruðu vikulega spurningalista sem var sérstaklega hannaður til að kanna umfang og alvarleika álagsmeiðsla. Að auki svöruðu þeir vikulega spurningu varðandi mat á huglægu álagi á kastöxl síðastliðna viku (innra axlarálag). Þátttakendur í öðrum hluta voru 31 leikmaður úr efstu deild kvenna í handbolta. Sömu mælingar og í fyrsta hluta voru framkvæmdar fyrir keppnistímabilið 2023-2024 og var þátttakendum aftur fylgt eftir í gegnum heilt keppnistímabil (29 vikur). Þátttakendur svöruðu einnig vikulega sama spurningalista og viðbótarspurningu um innra axlarálag og í fyrsta hluta. Að auki voru upplýsingar um fjölda skota í deildarleikjum fyrir hvern þátttakenda teknar saman til þess að leggja mat á ytra axlarálag. Tengsl á milli styrktar- og aflmælinga á undirbúningstímabili og algengi og alvarleika álagsmeiðsla í öxl voru metin með Spearman´s rho fylgnistuðli fyrir þátttakendur úr fyrsta og öðrum hluta. Áhrif styrktar- og aflmælinga á tengsl innra og ytra axlarálags og alvarleika axlarmeiðsla voru einnig könnuð með blandaðri dreifnigreiningu. Í þriðja hluta var framkvæmd þrívíddarhreyfigreining á uppstökkskasti hjá 41 leikmanni úr efstu deild karla og fór hún einnig fram fyrir keppnistímabilið 2022-2023. Tengsl á milli iv hreyfinga í neðri útlimum og bol og hreyfinga í kastöxl við framkvæmd kasts eftir uppstökk voru metin með Pearson´s og Spearman´s rho fylgnistuðlum. Óháð t-próf voru notuð til að meta mun á framkvæmd á milli leikmanna eftir leikstöðu og áhrif hreyfinga í neðri útlimum og bol á hornhraða innsnúnings í kastöxl voru metin með þrepaskiptri aðhvarfsgreiningu.Niðurstöður: Niðurstöður úr fyrsta hluta rannsóknar (karlkyns leikmenn) sýndu fram á tölfræðilega marktæka (neikvæða) fylgni á milli hámarksútsnúningsstyrks í öxl og algengi axlarmeiðsla yfir tímabilið (rs=-0.34, p=0.029). Innra axlarálag hafði marktæk áhrif á alvarleika axlarmeiðsla (p