Nr. 1/05 samlet - Dansk Sportsmedicin

the muscles show that T2-weigthed MRI scans may be applied to identify damaged
muscles from which enzymes are being released into the circulation, indicating loss of
sarcolemmal integrity. Furthermore, the reduced responses after the second bout indicate
the presence of the “repeated bout effect”.
6. CHONDRODYSPLASIA: A STUDY OF MATRIX CHANGES IN PATELLAR AR-
TICULAR CARTILAGE OF A 14-YEARS OLD BOY
Storgaard Peter1 , Nicolaisen Tom2 1 2 Interface Biotech A/S, Glostrup University Hospital, 2600 Glostrup; The Sports Clinic, Frederikssund
Sygehus, Frederikssund, Denmark
Introduction: Type II collagenopathies which relates to mutations in the gene encoding
the type II collagen molecules, includes a genetically heterogeneous group of disorders
with dysfunction of type II collagen hetero-fibrils during bone growth and maintenance
of articular surfaces. In this study, we carried out LM ( light microscopy ) and TEM (
transmission electron microscopy ) of articular cartilage and explant cultured chondrocytes
from a 14-years old boy with severe articular lesions of the left patella. Material
and methods: Loose articular pieces of cartilage were removed from patella during
arthroscopy. From these fragments were cultured 2 weeks at 37C/5% CO2 as cartilage
explants in _DMEM/F12 medium containing 15% FCS, antibiotic and ascorbic acid 2phosphate.
The remaining pieces - as well as final cultured chondrocytes obtained
from explant culturing - were processed for LM and TEM respectively. Discussion: LM
and TEM of the cartilage showed a sparse and eroded extra cellular matrix (ECM) containing
many empty and highly expanded lacunae involving the upper to lower cartilage
zones. Within the ECM, type II collagen hetero-fibril aggregation and chondrocytes
containing dilated rER with accumulated matrix proteins were identified. Matrix
accumulation within rER was also demonstrated in explant cultured chondrocytes.
Furthermore vesicles containing accumulated matrix proteins were identified intracellular
and at the plasma membrane, suggesting impaired assembly and “aborted”
secretion of aggregated matrix proteins to the ECM. Conclusions: Our findings indicate
that type II pro-collagen were abnormally formed and accumulated within the rER
of chondrocytes leading to collagen aggregates in a highly compromised ECM, together
with dead chondrocytes. We suggest, that mutant type II pro-collagen are misassembled,
secreted and incorporated into the ECM, where they exert a dominant negative
effect on the function of type II collagen hetero-fibrils. We further suggest, that this
phenotype is related to mutation(s) in the Co12A1 gene.
7. JUMP HEIGHT IS RELATED TO DYNAMIC RATE OF FORCE DEVELOPMENT
Jens Bojsen-Møller, Lars R. Rasmussen, S. Peter Magnusson, Michael Kjær, Per Aagaard
Institute of Sports Medicine Copenhagen/Team Danmark Test Center, Bispebjerg Hospital, Copenhagen,
Denmark
Introduction: Isolated muscular function is frequently evaluated using isokinetic or
isometric procedures, although the movement patterns do not resemble those of sports
and/or daily life. It therefore seems desirable to quantify muscular performance during
more functional motor tasks, such as those that include ‘stretch-shortening cycles’.
It has been suggested that the ability to exert muscle force rapidly, i.e. the contractile
rate of force development (RFD) is important for performance in high intensity muscle
actions, however RFD has mainly been assessed during isometric conditions. The present
study evaluated the day-to-day reproducibility of dynamic RFD measured during
counter-movement jumping (CMJ), and investigated its relation to jump performance.
Methods: Twenty-four male subjects performed six CMJ’s during standardized conditions
on a force plate. Three similar test-days were completed. Maximal jump height
(MJH) was determined by integration of the ground reaction force signal, and dynamic
RFD was determined as the average slope of the force-time curve from the instant of
peak eccentric velocity to +100ms. A Pearson product-moment correlation was computed
to assess the relation between MJH and dynamic RFD. Day-to-day reproducibility
was investigated for MJH and RFD by calculating r and CV for repeated measurements.
Data are presented as means±SD. Results: MJH: 32.9±5.5cm (Day 2), and
32.9±5.7cm (Day 3), r=0.97, CV=2.89%. Dynamic RFD: 1883±926N . s-1 . kg-0.33 (Day 2),
and 1849±967N . s-1 . kg-0.33 (Day 3), r=0.82, CV=10.25%. MJH (32.9±5.7cm) correlated
positively to dynamic RFD (1866±902 N . s-1 . kg-0.33), r=0.53, P