european college of sport science

IS-BM09 Bone and exercise
A novel finding of the present study is that 10 wks of SST lowered mRNA concentration of the stress-inducible HSP72 as well as the constitutive
HSP70 in females with work-related TM myalgia. Strength training is associated with changes in protein synthesis and degradation,
and since HSPs assist in these processes, the expression of HSP could increase initially but decline in the later phase of the training
period. Mechanisms exist, which are able to attenuate the HSP response and the observed down-regulation of HSP mRNA content in the
present study may reflect an improved cellular homeostasis of TM fibers. The GFT intervention also lowered the HSP72 mRNA content.
Induction of stress protein synthesis after moderate-intensity exercise may occur in both active muscle and in less active muscle, indicating
that the signal which initiates the stress response is produced by and affects the whole body. The existence of a generalized response
of skeletal muscle to physical stress could explain the present finding in GFT, which did not involve exercise of TM, that HSP72
mRNA content in TM was lowered after a prolonged training period. In conclusion: The decrease in stress-inducible HSP72 mRNA content
after 10 wks SST and GFT supports the notion of systemic signaling. However, only SST decreased the constitutive HSc70 underlining the
significance of involving the painful muscle in training for improved cellular homeostasis.
08:30 - 10:00
Invited symposia
IS-BM09 Bone and exercise
MUSCLE FORCE AND STIFFNESS AND THEIR IMPACT ON BONES
HANS SCHIESSL, PFORZHEIM
GERMANY
Without abstract submission
MUSCLE EXERCISE: HIGH SOPHISTICATED TECHNIQUE WITH VIBRATION EXERCISE
MARTIN RUNGE, RAINER RAWER, ESSLINGEN
GERMANY
Without abstract submission
MUSCLE & BONES IN MASTER ATHLETES AND IN SPACE.
DIETER FELSENBERG, BERLIN
GERMANY
Without abstract submission
08:30 - 10:00
Invited symposia
IS-BM02 Strength training B: Neuromuscular mechanisms
TRAINING EFFECTS ON THE CHARACTERISTICS AND BEHAVIOUR OF HUMAN MOTOR UNITS
DUCHATEAU, J.
UNIVERSITE LIBRE DE BRUXELLES
The force generating capacity of an isolated muscle is strongly associated with its cross-sectional area. However, the strength produced
during natural movements depends on the extent to which a muscle and its synergist and antagonist are activated by the nervous system
(2). Although strength training is known to induce hypertrophy of the muscle fibres, some studies have suggested that increase in
voluntary activation can also contribute to the improvement in performance. A greater activation can be the result of a more complete
recruitment of motor units (ensemble comprising a motor neurone, its axon and the muscle fibres innervated by this axon) and/or an
increase in discharge rate. In addition to the increase of the force produced by each motor unit after training (3), recent evidences indicate
that the maximal discharge rate attained by motor unit is enhanced without any change in synchronization (4). This neural adaptation
occurs mainly at the beginning of a training programme.
In many sports and activities of daily life, the ability to rapidly develop force is equally important, or even more important, than the maximal
force itself. Movements that are performed with maximal velocity are usually defined as ballistic actions (1). The maximal rate of force
development during a ballistic contraction is not only limited by muscle speed-related characteristics, but also by neural factors. Among
them, the capacity of the nervous system to recruit a great percentage of the motor unit pool at the onset of muscle activation and to drive
these units at a high discharge rate is an important aspect. In that context, it has been demonstrated that dynamic training consisting in
rapid contractions against a small load (30-40% of maximum) augments both the rate of force development and the instantaneous
discharge rate of motor units (5). In addition to the latter adaptation, the incidence of doublet discharges with an interval of less than 5 ms
is increased. These neural changes, that contribute to enhance the maximal rate of force development, appear to adapt specifically to
the training conditions. Together, these findings show that, in addition to intrinsic adaptations of the muscular system, the rate of force
development during a ballistic contraction is modulated by chronic changes in motor units discharge pattern.
516 14 TH
ANNUAL CONGRESS OF THE EUROPEAN COLLEGE OF SPORT SCIENCE