Increasing hip and knee flexion during a drop-jump task reduces tibiofemoral shear and compressive forces: implications for ACL injury prevention training

Although most ACL injury prevention programmes encourage greater hip and knee flexion during landing, it remains unknown how this technique influences tibiofemoral joint forces. We examined whether a landing strategy utilising greater hip and knee flexion decreases tibiofemoral anterior shear and compression. Twelve healthy women (25.9 ± 3.5 years) performed a drop-jump task before and after a training session (10–15 min) that emphasised greater hip and knee flexion. Peak tibiofemoral anterior shear and compressive forces were calculated using an electromyography (EMG)-driven knee model that incorporated joint kinematics, EMG and participant-specific muscle volumes and patella tendon orientation measured using magnetic resonance imaging (MRI). Participants demonstrated a decrease in peak anterior tibial shear forces (11.1 ± 3.3 vs. 9.6 ± 2.7 N · kg^?1; P = 0.008) and peak tibiofemoral compressive forces (68.4 ± 7.6 vs. 62.0 ± 5.5 N · kg^?1; P = 0.015) post-training. The decreased peak anterior tibial shear was accompanied by a decrease in the quadriceps anterior shear force, while the decreased peak compressive force was accompanied by decreased ground reaction force and hamstring forces. Our data provide justification for injury prevention programmes that encourage greater hip and knee flexion during landing to reduce tibiofemoral joint loading.     

Reviews

Pat Sadler, Hiroshima Shudo University, The Caring Child by Nancy Eisenberg. Cambridge, Mass, and London: Harvard University Press, 1992, hb ISBN 0 674 09725 4, pb ISBN 0 674 09726 2, US$8.95

Garry Hornby, University of Hull, Youth in Trouble: Educational Responses, by J. F. Schostak. London: Kogan Page, 1991. 192pp., pb. ISBN 0 7494 0372 1, np

Gordon Dimmock, Harold Hill Community School, Havering, ‘Some Way to Go’: A Pilot Study on the Appraisal of Educational Resources on Leaving Home and Homelessness, Leaving Home Project. London: Information Services Charity Limited, 1987. 56pp., £4.95

Gordon Dimmock, Harold Hill Community School, Havering, Experimental Project. Final Report, Leaving Home Project. London: Information Services Charity Limited, 1991. 30pp., £6

Gordon Dimmock, Harold Hill Community School, Havering, ‘Making the Break’: Choices and Decisions Facing Young People Leaving Home, by Philip Hope, edited by Catherine ByGott. London: CSV Advisory Service and Leaving Home Project, 1989. 157pp. plus VHS video ‘Cutting Loose’, 20 min., CSV, 1988. ISBN 0 907829 57 0, £28.25+£2.40 p. & p.

Don Baines, Anglia Polytechnic University, Teacher Training in Secondary Schools, by Rowie Shaw. London: Kogan Page Limited, 1992. 162pp., pb ISBN 0 7494 0637 2, £14.95

Gill Collins, Sovereign Centre Tutorial Unit, Issues: A Cross-Curricular Course for PSE, by John Foster. Hammersmith: Collins Educational, 1992. Pupil Book One, ISBN 0 00 327334 2, £4.95; Teachers Resources One, ISBN 0 00 327339 3, £7.25; Pupil Book Two, ISBN 0 00 327335 0, £4.95; Teachers Resources Two, ISBN 0 00 327340 7, £7.25; Pupil Book Three, ISBN 0 00 327336 9, £4.95; Teachers Resources Three, ISBN 0 00 3273415, £7.25; Pupil Book Four, ISBN 0 00 327337 7, £5.50; Teachers Resources Four, ISBN 0 00 327342 3, £7.95; Pupil Book Five, ISBN 0 00 327338 5, £5.50; Teachers Resources Five, ISBN 0 00 327343 1, £7.95     

Cognitive interference during competition among volleyball players with different goal orientation profiles

In this study, we examined interfering thoughts during sport competition among university volleyball players as a function of dominant goal orientation and outcome. In particular, we investigated the performance worries and thoughts of escape experienced while performing in athletes with high task and low ego orientation and athletes with high ego and low task orientation. Goal orientations were assessed before the start of a volleyball tournament, whereas cognitive interference was assessed on three different occasions after games. The results revealed no consistent differences for performance worries. In contrast, in all analyses we found that athletes with high ego and low task orientations reported more thoughts of escape when losing than when winning, and more thoughts of escape than athletes with high task and low ego orientations when winning or losing. The results support in part the suggestion that a high ego orientation, when not accompanied by a high task orientation, can be linked to motivationally maladaptive cognitions.     

Motivation for physical activity in young people: entity and incremental beliefs about athletic ability

Three studies are reported of children and youth aged 11-19 years (n = 3478) examining the nature of beliefs about athletic ability. Drawing on related research in academic, moral and stereotyping domains, development of a psychometric instrument assessing athletic ability beliefs is detailed. Support was found for a multidimensional hierarchical structure that is invariant across age and gender. Confirmatory factor analysis revealed a structure comprising two higher-order factors of entity and incremental beliefs underpinned by beliefs that athletic ability is stable and a gift (entity), and is open to improvement and can be developed through learning (incremental). Incremental beliefs, indirectly through a task goal orientation, and entity beliefs directly, predicted self-reported amotivation towards physical education and sport. On the other hand, enjoyment of physical activity in youth was predicted directly by task orientation and incremental beliefs. Predictions concerning the moderating role of perceived competence were not supported. Our findings highlight the importance of ability beliefs and goals in understanding the determinants of physical activity in children and youth.     

The influence of self-efficacy and past behaviour on the physical activity intentions of young people

The aim of the present study was to assess the influence of self-efficacy and past behaviour on young people's physical activity intentions using an augmented version of Ajzen's Theory of Planned Behaviour. We hypothesized that self-efficacy would exhibit discriminant validity with perceived behavioural control and explain unique variance in young people's intentions to participate in physical activity. We also expected that past physical activity behaviour would attenuate the influence of attitude, subjective norms, perceived behavioural control and self-efficacy on intention. The sample comprised 1,152 young people aged 13.5 +/- 0.6 years (mean +/- s) who completed inventories assessing their physical activity intentions, attitudes, subjective norms, perceived behavioural control, self-efficacy and past physical activity behaviour. A confirmatory factor analysis demonstrated that the constructs of the Theory of Planned Behaviour achieved discriminant validity. Furthermore, the measures of attitudes, subjective norms, perceived behavioural control and self-efficacy were significantly related to their respective belief-based measures, supporting the concurrent validity of the measures of the Theory of Planned Behaviour. A non-standard structural equation model demonstrated that attitude and self-efficacy were strong predictors of physical activity intention, but perceived behavioural control and subjective norms were not. Self-efficacy attenuated the influence of attitudes and perceived behavioural control on intention. Past behaviour predicted intention directly and indirectly through self-efficacy and attitude. The present findings demonstrate that young people with positive attitudes and high self-efficacy are more likely to form intentions to participate in physical activity. Furthermore, controlling for past physical activity behaviour revealed that the unique effects of self-efficacy and attitudes on young people's physical activity intentions were unaltered.