European Journal of Applied Physiology

, Volume 115, Issue 5, pp 1135–1145 | Cite as

Influence of short-term unweighing and reloading on running kinetics and muscle activity

  • Patrick SaintonEmail author
  • Caroline Nicol
  • Jan Cabri
  • Joëlle Barthelemy-Montfort
  • Eric Berton
  • Pascale Chavet
Original Article



In running, body weight reduction is reported to result in decreased lower limb muscle activity with no change in the global activation pattern (Liebenberg et al. in J Sports Sci 29:207–214). Our study examined the acute effects on running mechanics and lower limb muscle activity of short-term unweighing and reloading conditions while running on a treadmill with a lower body positive pressure (LBPP) device.


Eleven healthy males performed two randomized running series of 9 min at preferred speed. Each series included three successive running conditions of 3 min [at 100 % body weight (BW), 60 or 80 % BW, and 100 % BW]. Vertical ground reaction force and center of mass accelerations were analyzed together with surface EMG activity recorded from six major muscles of the left lower limb for the first and last 30 s of each running condition. Effort sensation and mean heart rate were also recorded.


In both running series, the unloaded running pattern was characterized by a lower step frequency (due to increased flight time with no change in contact time), lower impact and active force peaks, and also by reduced loading rate and push-off impulse. Amplitude of muscle activity overall decreased, but pre-contact and braking phase extensor muscle activity did not change, whereas it was reduced during the subsequent push-off phase.


The combined neuro-mechanical changes suggest that LBPP technology provides runners with an efficient support during the stride. The after-effects recorded after reloading highlight the fact that 3 min of unweighing may be sufficient for updating the running pattern.


Running Unweighing Reloading SSC EMG GRF 



Active peak force


First 30 s sample of each running condition


Body weight


Center of mass


Vertical displacement of CoM during the braking phase




Last 30 s sample of each running condition


Vertical ground reaction force


Ground reaction force


Gastrocnemius lateralis


Gastrocnemius medialis


Impact peak force


Vertical stiffness


Lower body positive pressure


Minimal force after IPF




Rating of perceived exertion




Stretch-shortening cycle


Tibialis anterior




Vastus lateralis


Vastus medialis



We are particularly grateful for the assistance given by Dr. Antoine Morice and Dr. Cedric Morio for data analyses.

Conflict of interest

None of the authors had any financial or personal conflict of interest with regard to this study.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  • Patrick Sainton
    • 1
    Email author
  • Caroline Nicol
    • 1
    • 2
  • Jan Cabri
    • 2
  • Joëlle Barthelemy-Montfort
    • 1
  • Eric Berton
    • 1
  • Pascale Chavet
    • 1
  1. 1.Aix Marseille Université, CNRS, ISM UMR 7287MarseilleFrance
  2. 2.Department of Physical PerformanceNorwegian School of Sport SciencesOsloNorway

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