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New PhD thesis on reliability and methodological issues in biomechanics


Friday, January 8 PhD-student Kam-Ming Mok will defend his PhD-thesis "Reliability and methodological concerns of vertical drop jumping and sidestep cutting tasks – Implications for ACL injury risk screening" at the Norwegian School of Sport Sciences.

Every year, 1.500-2000 Norwegians will get a surgery following an injury to the anterior cruciate ligament (ACL). For many athletes, this severe knee injury can be the end of a promising sports career.

As many of these injuries occur in a cutting or landing situation with the athlete having poor knee control, a biomechanical test, a vertical drop jump (VDJ) test, often is used to identify athletes at risk for knee injuries.

Setting up a VDJ test is simple, whether visually rated in the field or measured in a lab-setting using more advanced motion analysis systems.

However, various methodological and reliability issues should be studied prior to the systematic use of this and other similar tasks as formal screening tools.

Ming (picture above, photo Jarle Stokland) has focused his PhD-work on investigating the reliability of biomechanical variables assessed during a VDJ and side-step cutting as well as the effect of various marker set configurations on knee kinematics. Also, Ming evaluated the additional effect of an overhead target to the VDJ-test compared to the test without an overhead target on knee biomechanics.

Shortly a summary of his main results

The reliability of knee biomechanics in both the VDJ and side-step cutting task is good and feasible for screening purposes. However, using different marker configurations displayed significantly different results, highlighting the need for a standardized set up of markers and guidelines to minimize variation in measurements.

An overhead target is unlikely to increase the knee moments and motion variables in elite ball team players.

These findings, however, do not answer the research question whether knee motion and moments measured in a VDJ-test indeed are associated with an increased injury risk.

The following 4 articles comprise the PhD-thesis of Ming

1) Reliability of knee biomechanics in a vertical drop jump task in elite female athletes

2) Reliability of knee biomechanics in two cutting tasks in elite female handball and football players

3) The effect of thigh marker placement on knee valgus angles in vertical drop jumps and sidestep cutting

4) The effect of an overhead target in a VDJ test

Associate professor Tron Krosshaug and Professor Roald Bahr served as supervisors for Ming. 

Read more about Ming´s projects

Ming is now back in Hong Kong where he has a lecture position.

Program for February 13 (Place: Norwegian School of Sport Sciences, Oslo)

10:15-11:00: Trial lecture «Review of existing ACL injury risk prevention programs and their effectiveness»

13:00-15:30: PhD defense


1.opponent: Associate professor Tine Alkjær, University of Copenhagen, Denmark
2.opponent: Dr Jos Vanrenterghem, University of Leuven, Belgium

Head: Professor Jan Cabri, Norges idrettshøgskole, Norwegian School of Sport Sciences, Norway

Trial lecture and PhD defense will be held in English and are open for public. WELCOME