The aims of this study were to 1) determine if hypergravity (HG) squats can produce foot forces similar to those measured during 10-repetition maximum (10RM) squats using weights under normal 1-G(z) condition, and 2) compare the kinematics (duration and goniometry) and EMG activities of selected joints and muscles between 10RM and HG squats of similar total foot forces. Eight men and six women [27 yr (SD 4), 66 kg (SD 10)] completed ten 10RM [83 kg (SD 23)] and 10 HG squats (2.25-3.75 G(z)). HG squats were performed on a human-powered short-arm centrifuge. Foot forces were measured using insole force sensors. Hip, knee, and ankle angles were measured using electrogoniometers. EMG activities of the erector spinae, biceps femoris, rectus femoris, and gastrocnemius were also recorded during both squats. All subjects were able to achieve similar or higher average total foot forces during HG squats compared with those obtained during 10RM squats. There were no differences in total duration per set, average duration per repetition, and goniometry and EMG activities of the selected joints and muscles, respectively, between 10RM and HG squats. These results demonstrate that HG squats can produce very high foot forces that are comparable to those produced during 10RM squats at 1 G(z). In addition, the technique and muscle activation are similar between the two types of squats. This observation supports the view that HG resistance training may represent an important countermeasure to microgravity.
This report was prepared a s. an account of work sponsored by t h e. United States Government. Neither the United States nor the United States Atomic Energy ~o m t n i s s i o n , nor any of their employees, nor any of their contractors, subcontmctors, or their employees, makes any. warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness or. usefulness of any information, apparatus, product'or process disclosed, o r represents that its use would not infringe privately owned rights.. . DISTRIBUTION OF THIS 00CUM.ENT IS UHLIMIT k ACKNOWLEDGMENTS Appreciation is extended to H. D. Curet and L. J. Ybarrondo for their help in guiding the task to completion and to T. E. Curry and K. A. Dietz for their help and suggestions in preparation of the final copy.
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