Table 5.

Studies with Twin Correlations that are corrected for PA levels or Unique Environmental Effects (twins may not be discordant for PA).

Outcomes	H-effect	PA Effect	MZ (n)	DZ(n)	Sex	PA Measurement	Comments	Ref
Weight gain	↓ correlation in inactive		1571	3029	B	Questionnaire of Physical activity levels at baseline	Finnish twin study. At all activity levels MZ twins had greater hereditability than DZ twins.	(231)
Waist Circumference		↑ 2.5 cm in low PA twin	287	189		Questionnaire in 1998 and 2002. Only looking at leisure and occupational PA	No analysis for discordant PA. If twins had large genetic susceptibility then low PA resulted in larger increase in WC	(266)
BMI		N.S.
Waist Circumference	76(M)–77(F)%	21(M)–22(F)%	71	75	B	Questionnaire	African Americans aged 22–88 from Carolina African American Twin Study of Aging. All effects are unique environemental not just PA levels.	(374)
Waist-Hip Ratio	59(M)–56(F)%	36(M)–38(F)%
BMI	89(M)–73(F)%	11(M)–27(F)%
Discordant for BMI by at least 3.		N.S.	23		B	Interviews and Questionnaire for PA	No significant effects of PA on the discordance of overweight prevalence.	(214)
Discordant for obesity		↓ fitness (8%) and activity (15%) in Obese twin	14		M	VO2max and Baecke leisure time PA	From FinnTwin study – obese also had lower adipose mitochondrial gene expression	(362)
Subscapulantrice ps BF ratio	24%		265		M	“crude” measure of PA	PA was inversely related to adjusted waist c i re umf ranee	(468)
waist circumference	46%
Diastolic BP	35%	5%	71	104	B	Interview: Lifetime exercise divided into power, aerobic, or other	Aerobic exercise in adolescence lifetime high intensity aerobic associated with low diastolic BP throughout life (mean age of 50 at study time).	(236)
Aerobic exercise amount	44%	N.S.
“Augmentation index”, or systemic arterial stiffness		↑ Sig in high genetic risk group when inactive	53	262 + 54 singlet ons	F	Questionnaires		(209)
MZ subjects that are discordant for hypertension		Hypertensive twin ↑being inactive (after military service)	281		M	Survey from the National Heart, Lung, and Blood Institute (NIH)	Twins whom are veterans of WWII aged 55–66. Surveyed at time of entry to military and time of study.	(78)
HDL cholesterol	Correctin g for genetics prevent correlatio n	↑correlation btw exercise and HDL	179	255	F	Questionnaire (one question about PA)	Kaiser Twin Registry in Oakland, CA. aged 18–85.	(105)
Lumbar spine disk degeneration	74%	N.S.	172	154	B	Interviewed about weight bearing exercise	No effect of adjustment for exercise on lumbar or cervical disk degeneration	(456)
Lumbar spine disk degeneration	73%	N.S.
total body BMC (DEXA)		1.2% less in inactive twin/hour of less exercise	30	26		Questionnaire for weight bearing exercise	Associated was not present in pre-pubescent twins	(254)
leg BMC		↓ 1.4% in inactive
Spine BMC		↓ Sig in inactive
BMD		N.S.	122	93	F	12 month recall questionnaire for sport activity	10–26 yr old from Australian twin registry.	(577)
Smoking Likelihood at follow up (about 4 yrs)		↑ 3.36x for inactive twin to be regular smokers	97	339	B	Survey for twins discordant for PA (3 categories used) at baseline	Adolescents from a Finnish Twin Registry. Did not analyze by zygosity.	(290)
Discordant Prevalence of non-Alzheimer dementias		↑Risk Correlated with Physical inactivity	106			Questionnaire administered 30 years before	Swedish twin registry average age of first questionnaire was 48	(195)
Twins discordant for chronic fatigue syndrome – cognitive functioning tests pre-post max test	Cognitive tests did were N.S.	No relationship to chronic PA was made	21		B (19 M, 2F)	Acute Cycle ergometerto max	Exercise caused no change in cognitive functioning acutely.	(103)
Various Cognitive Functions	>15%	<80%	1,432	1,715 + 268,496 siblings	M	Cycle W max/kg	PA effect for all non-shared environmental effects.	(1)

B = both;

DZ= dizygotic;

F = female;

H = heredity effect;

M = male; monozygotic;

N.S. = non-significant;

n = number of subjects.

↑ = increase;

↓ = decrease