Eija Haapalainen Perttu Laurinen Pekka Siirtola Juha Röning Hannu Kinnunen Heidi Jurvelin Exercise energy expenditure estimation based on acceleration data using the linear mixed model. 131-136 2008 IRI http://dx.doi.org/10.1109/IRI.2008.4583018 conf/iri/2008 db/conf/iri/iri2008.html#HaapalainenLSRKJ08