Table 2.

Summary of Studies Examining the Association Between Physical Activity and Indicators of Bone Health in Children <6 Years of Age.

Study (title, citation)	Subjects (age, sex, etc.)	Sample Size	Study Design	Physical Activity Exposure	Bone Outcomes	Findings
Binkley, 2004 (27)	3–5 years old at baseline (males and females) mostly white	161	One year post trial follow-up	Researcher delivered Intervention gross motor vs fine motor PA (5/d week, 15–20 min/d) and calcium supplementations	pQCT, DXA measured BMC and BA leg, periosteal and endosteal circumference tibia	Children in gross motor skill group maintained greater tibial periosteal circumference difference 1-year post intervention compared to fine motor.
Erlandson MC, 2011 (28)	4–6 years old at baseline (males and females) mostly white	163	Prospective Cohort Measured annually for 4 years	Parent report (hrs/wk) of recreational or precompetitive gymnastics	Dual-energy x-ray absorptiometry (DXA) measured total body, lumbar spine, and femoral neck bone mineral content (BMC)	Compared to non-gymnasts in other recreational sports, gymnasts had 3% more total body BMC and 7% femoral neck BMC.
Gruodyte-Raciene R, 2013 (29)	4–6 years old at baseline (males and females) mostly white	165	Prospective Cohort Measured annually for 4 years	Parent report (hrs/wk) of recreational or precompetitive gymnastics	DXA and hip structural analysis program (HSA) estimated cross-sectional area (CSA), section modulus (Z), cortical thickness (CT) at narrow neck (NN), intertrochanter (IT), shaft (S) of hip	Compared to non-gymnasts in other recreational sports, gymnasts had 6% greater NN CSA, 7% NN Z, 5% greater IT CSA, 6% greater IT Z and 3% greater S CSA.
Jackowski SA, 2015 (30)	4–6 years old at baseline (males and females) mostly white	127	Prospective Cohort Measured over 3 years	Parent report (hrs/wk) of recreational or precompetitive gymnastics	Peripheral quantitative computed tomography (pQCT) measured distal and shaft measures of bone structure at radius and tibia	Compared to non-gymnasts in other recreational sports, gymnasts had greater total bone area and total BMC at distal radius (8 to 21% difference).
Janz KF, 2006 (31)	4 −6 years old at baseline (males and females) mostly white	370	Prospective Cohort with a 3 year follow-up	Device-measured MVPA 3000 ct/mn	DXA measured BMC hip, trochanter, spine, and total body	Compared to children maintaining low levels of PA, children maintaining high levels of PA throughout study accrued 14% more trochanteric BMC and 5% more total body BMC.
Janz K, 2007 (32)	4–6 years old at baseline (males and females) mostly white	468	Prospective Cohort Measured 3 times (baseline, approximately 8 yr. and 11 yr.)	Device-measured MVPA 3000 ct/mn	DXA and HSA estimated bone structure femoral neck Z and CSA	PA positive independent predictor of Z and CSA. 40 min/d compared to 10 min/d equated to 3–5% greater CSA and Z
Janz KF, 2014 (33)	4–6 years old at baseline (males and females) mostly white	530	Prospective Cohort Measured 6 times (baseline, approximately 8, 11, 13, 15, and 17 yr.)	Device-measured MVPA (Evenson 2296 ct/min)	pQCT, DXA and HSA estimated BMC and bone structure of hip (CSA, Z) and tibia (bone stress index, polar moment of inertia)	Greater accumulation of MVPA resulted in great bone mass and structure at age 17 years
Janz KF, 2010 (34)	4–6 years old at baseline (males and females) mostly white	333	Prospective Cohort Measured 3 times baseline, approximately 8, and 11 yr.)	Device-measured MVPA 3000 ct/min	DXA measured BMC total body, hip, spine	Children at highest quartile of MVPA at baseline had 4–14% more BMC at age 8 and 11 years when compared to peers in lowest quartile. Results attenuate when controlled for baseline BMC but remained significant in boys.
Specker BL, 2003 (35)	3–5 years old at baseline (males and females) mostly white	239	One year randomized control trial	Researcher delivered Intervention gross motor vs fine motor PA (5/d week, 15–20 min/d) and calcium supplementations	pQCT, DXA measured BMC total body and leg, periosteal and endosteal circumference tibia	Children in gross motor skill group have greater tibial circumferences compared to fine motor.
Specker BL, 1999 (36)	6 months old at baseline (males and females) white	72	One year randomized control trial with outcome measures at baseline, 9, 12, 15 and 18 months.	Researcher delivered Intervention gross motor vs fine motor PA (5/d week, 15–20 min/d) and calcium supplementations	DXA measured BMC total body	No difference at follow-up between group.