2007, Piran, Slovenia

Environmental Ergonomics XII
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007
MAXIMAL EXPLOSIVE POWER OF THE LOWER LIMBS
ADAPTATIONS TO 35-DAY BED REST:
RESULTS OF THE 2006 VALDOLTRA BED REST CAMPAIGN
Stefano Lazzer 1 , Giovanni Messina 1 , Ivan Zadro 1 , Renzo Pozzo 1 , Marco Narici 1,2 ,
Olivier Seynnes 2 , Maarten de Boer 2 , Igor B. Mekjavic 3 , Rado Pisot 4 , Gianni Biolo 5 ,
Guglielmo Antonutto 1 , Pietro Enrico di Prampero 1
1 Dipartimento di Scienze e tecnologie Biomediche – MATI Centro di Eccellenza -
Università di Udine, P.le M. Kolbe 4, 33100 Udine, Italy
2 Centre for Biophysical and Clinical Research into Human Movement (CRM),
Manchester Metropolitan University, Alsager Campus, Alsager, ST7 2HL, Cheshire,
UK
3 Department of Automation, Biocybernetics and Robotics, Institute Jozef Stefan,
Ljubljana, Slovenia
4 Institute for Kinesiology Research (IKARUS), University of Primorska,
Garibaldijeva 1, 6000 Koper, Slovenia
5 Dipartimenti di Scienze Cliniche, Morfologiche e Tecnologiche – Clinica Medica –
Università di Trieste - Ospedale di Cattinara Strada di Fiume 447, 34149 Trieste,
Italy
Contact person: pprampero@makek.dstb.uniud.it
INTRODUCTION
Data obtained before and immediately after the Euromir 1994 and 1995 missions have
shown that maximal power during very short “explosive” efforts of the lower limbs
(MEP) of 0.25 to 0.30 seconds duration was reduced to about 67% after one month,
and to about 45% (of pre-flight values) after about six months, space flight (Antonutto
et al., 1999). In these same subjects, the muscle mass of the lower limbs declined by
only 9-13% (Zange et al., 1997). These data suggest that a substantial fraction of the
observed decreases of maximal power may be due to a deterioration of the motor coordination
brought about by absence of the constant pull of gravity. A similar, albeit
less impressive, fall of maximal explosive power was observed after 42 days of bedrest
(BR) in five non-athletic male volunteers, in which case the maximal explosive
power was reduced to 76% of pre BR value (Ferretti, 1997; Ferretti et al., 2001), as
compared with 67% after 31 days space flight.
The aim of the present study was to further investigate the effects of BR on muscle
force, power and EMG during MEP exercises.
METHODS
Ten healthy males (age 22.3 ± 2.2 years) underwent 35-day horizontal BR without
countermeasures in the clinical facility of the Orthopaedic Hospital Valdoltra,
Ankarana (Slovenia). Each participant gave written informed consent to this
investigation that was approved by the local Ethics Committee.
Three days before bed rest (BR-3) and on the first day of recovery (R+0) MEP of the
lower limbs was measured, during pushes with both feet on two force platforms
located on a dedicated multipurpose ergometer dynamometr (EXER, figure 1).
Overall (right + left limb) force and speed of the consequent back-wards movement of
the carriage-seat on which the subjects sat, were recorded by appropriate transducers.
EMG recordings were simultaneously collected from thigh muscles (vastus lateralis
and biceps femori). In a different experimental section, forces developed during
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