https://www.massgeneral.org/doctors/19846/kirstin-birtwell
Kirstin Birtwell, PhD -
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https://www.topendsports.com/testing/tests/birtwell-40m-test.htm
Birtwell 40m Shuttle Test Calculator - Score Interpreter and VO2max Estimator
Calculate your Birtwell 40m shuttle test results instantly. Convert level and rep scores to fitness ratings, estimated VO2max, and compare to rugby player...
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https://www.celiabirtwell.com/
Celia Birtwell
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https://yougov.com/en-gb/topics/sports_personality/Ian_Birtwell
Ian Birtwell popularity & fame | YouGov
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