title: Ground reaction forces and heart rate profile of aerobic dance instructors during a low and high impact exercise programme.
abstract: OBJECTIVE
  The magnitude of ground reaction forces (GRF) has been associated, although never verified, with the high incidence of lower extremities injuries in aerobic dance (AD) instructors. Moreover, during their working activities AD instructors have demonstrated HR levels, such as 70% HRmax, values, more in training rather in working status. This study was designed to investigate GRF and heart rate (HR) exhibited by AD instructors of both genders, during a simulated AD instruction, from the perspective of accepted occupational workloads.
  
  
  METHODS
  Fourteen females and 14 males instructors performed a 35 min AD exercise programme (warm up--low impact (LI) interval--in high impact (HI) interval--cool down). Four GRF measurements were taken during LI and HI time intervals, respectively. HR was recorded throughout the whole experimental procedure and was synchronised to GRF measurements.
  
  
  RESULTS
  All GRF and HR values were significantly increased in HI exercise (p<0.05) with a non significant (p>0.05) time effect for GRF. In both LI and HI exercises, females demonstrated significantly higher vertical but lower lateral GRF (p<0.05) and significantly shorter cycles of movement (p<0.05) while in HI exercise they had significant longer flight times (p<0.05). For both genders, HR was kept at 70% and 80% of HR(max-calc) and RHR was 60% and 70%, during LI and HI intervals respectively, with females showing a trend, though non-significant, for higher HR values.
  
  
  CONCLUSIONS
  The gender specificity of the significant vertical and lateral GRF pattern differences, may possibly be associated with the significant anthropometric differences of male and female AD instructors. HR(max-calc) and RHR exceeded the accepted occupational levels rising to training status levels. We suggest that AD instructors take up such instructing methods which allow them to minimize the magnitude or the rate of GRF, as well as HR levels, developed in the course of their working hour.
authors.affiliation: Laboratory of Sport Biomechanics, Faculty of Physical Education and Sport Science, National and Kapodistrian University of Athens, Athens, Greece. erousan@cc.uoa.gr
authors.forename: E N
authors.initials: EN
authors.lastname: Rousanoglou
authors.forename: K D
authors.initials: KD
authors.lastname: Boudolos
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D003615:Dancing / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005260:Female; D005528:Foot / Q000502:physiology; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D012737:Sex Factors