Measurements for improvement of running capacity. : Physiological and biomechanical evaluations

Detta är en avhandling från Stockholm : Karolinska Institutet, Department of Physiology and Pharmacology

Sammanfattning: Introduction: Running is included in a large number of sports and one of the most well investigated modes of locomotion in both physiology and biomechanics. This thesis focuses on how some new methods from both areas may be used to capture running capacity in mid-distance and distance running from laboratory and field recordings. Measurement of running economy is included and defined as oxygen uptake at a given submaximal velocity in a steady-state condition. Running economy is mostly recorded on motor driven, level treadmills and consequently does not include the frontal air resistance effect. However, running economy is the sum from of a number of sub-factors. Stride characteristics and vertical displacement (Vdisp) of the centre of mass (CoM) are two of them and here novel measuring methods are described and validated to get a wider spectrum of factors that influence running economy. Aims: The aim of the work presented in this thesis was to describe and validate novel and easy-to-handle methods for improved capture of running economy with some of its subfactors. The intention is later to integrate and refine the methods mentioned for regular use when analyzing and monitoring runners capacity. Methods: The outcome of an incremental lactate-threshold test (4x4 min) was compared with and without 30 s stops for blood sampling on a treadmill (n=10). A lightweight, portable, metabolic device was validated against the Douglas bag method (DBM) in a wide range of VO2 during ergometer cycling, and thereafter used for comparison of running economy and lactate threshold measurements during treadmill and indoor track running. Further, the device was compared to the DBM during treadmill running (n=14). An infrared radiation device emitting a dense web of 40 IR beams over the running surface was validated with respect to stance-phase duration against force plate in overground running and a contact shoe during treadmill running (n=14). The Vdisp of the CoM was measured with a position transducer and an accelerometer and compared to the output of an optoelectronic motion capture system during treadmill running (n=13). Results: Lactate-threshold running-velocity results were equal during continuous running and running with 30 s intervals. During ergometer cycling the portable device was valid and reliable in a wide range of measurements and during track running the device showed a VO2 cost approximately 6% higher than during treadmill running, most probably expressing the air resistance. The IR device demonstrated systematically an 11.5 ±8.4ms longer stance duration than the contact shoe over a wide range of velocities. Vdisp measuredwith a one-point position transducer somewhat overestimated (7 mm) the Vdisp CoM from the optoelectronic system, but can be compensated for. Conclusions: Blood sampling may, preferably be performed with 30 s interruptions of running during lactate threshold testing on treadmill as no difference from sampling during continuous running was detected. Running economy measurements with the portable metabolic device were reliable for running on treadmill and track, but overestimated VO2 with 5-6% compared to DBM on the treadmill. The convenient IR mat and position transducer may well be used to capture stride characteristics and CoM Vdisp during treadmill running.

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