Genetic Influences on Individual Differences in Exercise Behavior during Adolescence

Table 1

Zygosity of participating twin pairs for the total sample and the different age groups (complete twin pairs added in parentheses).

	Total sample	13-14 yr	15-16 yr	17–19 yr
MZM	662 (585)	211 (197)	282 (249)	169 (139)
DZM	567 (465)	201 (170)	210 (184)	156 (111)
MZF	1042 (918)	343 (317)	380 (333)	319 (268)
DZF	738 (621)	231 (207)	265 (225)	242 (189)
DOS	1359 (1025)	516 (428)	494 (372)	349 (225)

Note. MZM: monozygotic male twin pair; DZM: dizygotic male twin pair; MZF: monozygotic female twin pair; DZF: dizygotic female twin pair; DOS: dizygotic opposite-sex twin pair.