Time Spent in Sedentary Activity Is Related to Gross Motor Ability During the Second Year of Life

Abstract

Sedentary activity occupies a substantial amount of time during early childhood, with these habits influenced by changing trends in screen time for very young children. Among school-aged children, motor ability is inversely related to sedentary activity. However, the concept of sedentary activity is rarely investigated in toddlers, and thus little is known concerning its relationship with motor development during this rapidly changing and early period of life. Among two groups of toddlers, aged 18 months (N = 26) and aged 24 months (N = 16), this study investigated cross-sectional correlations of motor development (Bayley Scales of Infant Development—III) with daily sedentary activity (accelerometers). In both groups, gross motor ability, but not fine motor ability, was inversely correlated with time spent in sedentary activity. At 18 months, gross motor raw scores inversely correlated significantly with time in sedentary activity (r = −.533, p < .001) but fine motor raw scores did not (r = .182, p = .441). Also, at 24 months, gross motor raw scores inversely correlated with time in sedentary activity (r = −.563, p = .029), while fine motor raw scores did not (r = −.112, p = .425). These findings add important missing knowledge to the empirical literature regarding sedentary activity in toddlers and its relationship to emerging motor development. Future work might investigate best practices for measuring sedentary activity in this age-group and mechanisms behind its relationship with gross motor skills.

Keywords

toddler child motor development accelerometer Bayley Scales of Infant Development—III motor skills

Introduction

Time spent in sedentary behavior is associated with poor motor performance in children of preschool age and older (Fisher et al., 2005; Hardy, Reinten-Reynolds, Espinel, Zask, & Okely, 2012; Williams et al., 2008; Wrotniak, Epstein, Dorn, Jones, & Kondilis, 2006). This association supports the Positive Developmental Trajectories of Health model (Robinson et al., 2015), wherein motor competence, perceived motor competence, and health-related fitness interact to produce either positive or negative trajectories of health through the lifespan. The earliest indication of support for this model includes preliminary and tangential evidence in infants, wherein slower leg kicking frequency correlates with later acquisition of particular motor milestones (McKay & Angulo-Barroso, 2006) and walking (B. D. Ulrich & Ulrich, 1995). Other than these findings, there is limited evidence regarding sedentary behavior and motor development during the first two years of life.

The sedentary behaviors of infants and toddlers have captured researchers’ interest but mostly in the form of electronic screen time in these age groups. One study in 6-month-olds indicated that less sedentary time is associated with acquiring more sleep (Hauck, Zott, Felzer-Kim, & Adkins, 2018). Beyond this finding and screen time research, very little is known about sedentary activity in children under two years of age besides screen time research (Downing, Hnatiuk, & Hesketh, 2015). Although it is still unclear whether sedentary activity is a determinant of negative health consequences appearing by preschool, it is clear that screen time does have early cognitive and physical risks; a systematic review of sedentary behaviors before the age of 5 years found a dose–response relationship between television watching and both decreased psychosocial and cognitive development and increased adiposity (LeBlanc et al., 2012). This knowledge has prompted screen time recommendations from the American Academy of Pediatrics (Council on Communications and Media, 2016). However, there are no guidelines regarding the broader concept of sedentary activity in infants and toddlers, perhaps due to a paucity of research, and, therefore a lack of consensus regarding a definition or measurement of sedentary activity in infants and toddlers.

Rising levels of sedentary activity in developed countries and corresponding health consequences may be illuminated by investigations of sedentary activity in infants and toddlers, as this may be a time period in which lifelong sedentary patterns have their origins (Jones, Hinkley, Okely, & Salmon, 2013). A systematic review documented that 2-5-year-old children spend about 12 hours per day in a sedentary manner, with wide ranging reports of 23-94% of various monitoring periods spent in a sedentary fashion (Hnatiuk, Salmon, Hinkley, Okely, & Trost, 2014). In 2014, over 90% of infants in a low-income sample were exposed to television by two months of age, spending an average of 346 minutes per day (over five hours) around a television (Perrin et al., 2014). A study in Australia reported that preschoolers spent 301 minutes each day sedentary, with 109 minutes per day in screen time, adjusting for childcare attendance (Downing, Hinkley, Salmon, Hnatiuk, & Hesketh, 2017). In the context of this limited past research, this study aimed to measure the cross-sectional relationships of sedentary activity and motor development at two specific developmental time points: 18 months and 24 months.

Method

Participants

We recruited and enrolled 42 participants: (a) 26 participants aged within two months of 18 months of age and (b) 16 participants aged within two months of 24 months of age. We recruited participants through local children’s activity centers and university listserves. Our two exclusion criteria included any medical diagnosis known to influence the motor domain or premature birth (<37 weeks gestation). Participant characteristics are presented in Table 1.

Table 1.

Participant Descriptive Information.

	18 months				24 months
	Mean	SD	N	%	Mean	SD	N	%
Age	18	0	26		24.18	0.891	16
Gender
Female			15	57.7			6	37.5
Male			11	42.3			10	62.5
Race
White			22	84.6			8	50.0
Black			2	7.7			3	18.8
Asian			2	7.7			5	31.3
Siblings
0			9	34.6			5	31.3
1			11	42.3			8	50.0
2			5	19.2			3	18.8
3			0	0			0	0
4			1	3.8			0	0
SES
HS			2	7.7			0	0
SC			4	15.4			0	0
AD			2	7.7			0	0
BD			6	32.1			5	31.3
GD			12	46.2			10	62.5
BSID motor raw scores
Gross motor	49.18	2.54	22		56.19	2.56	16
Fine motor	36.55	1.90	22		38.75	4.47	16
Total motor	85.73	3.19	22		94.94	6.43	16
Ponderal Index (g/cm³)	2.76	0.08	22		3.22	0.40	16
Accelerometry
Sedentary PA (minutes per day)	313.14	103.73	20		394.53	84.16	15
Wear time (minutes)	2895.29	2895.29	20		3043.15	906.00	15
Wear time (minutes per day)	513.83	141.44	20		490.31	152.90	15
Days worn	5.50	1.10	20		6.60	1.12	15

Note. SD = Standard deviation; N = number of participants; % = percentage of age-group; SES = socioeconomic status; HS = mother high school educated; SC = mother has some college; AD = mother has associate’s degree; BD = mother has bachelor’s degree; GD = mother has graduate degree; BSID = Bayley Scales of Infant Development—III; PA = physical activity.

Procedures

All participants’ parents gave informed consent for their infants to participate. Caregivers filled out a brief health and demographics questionnaire before data collection occurred. Data collection took place with a caregiver present.

Motor Development

We administered to all participants the Fine and Gross Motor subtests of the Bayley Scales of Infant Development-3rd edition (Bayley, 2006). Rather than standard scores, we used raw scores, both to create variables unbounded by the percent scale and because age adjustment was unnecessary, considering the consistent age of the sample at each time point. Participants were evaluated using procedures detailed in the administration manual.

Daily Sedentary Activity

All infants independently walked at the time of their assessment appointment. Therefore, for both groups, we were able to use previously published methods to measure daily sedentary time, rather than methods for prelocomoting infants (Pitchford, Ketcheson, Kwon, & Ulrich, 2017). Specifically, we measured sedentary activity with an actigraph accelerometer (GT3x+, Pensacola, FL) secured at the right hip. We set a minimum wear time of three days for three hours per day (Cliff, Reilly, & Okely, 2009) and a nonwear period of zero accelerometer movement counts for 20 minutes. We applied cut-off points to characterize epochs as sedentary (0–48 counts/15 seconds), light (49–418 counts/15 seconds), or moderate (> 418 counts/15 seconds) intensity (Trost, Fees, Haar, Murray, & Crowe, 2012), and we averaged the daily time participants spent in these intensities.

Statistical Approach

We used Pearson correlations to investigate the cross-sectional relationships of motor development with daily sedentary time. Scatter plots visually represented these relationships. All statistical procedures were performed using SPSS version 24 (IBM Corp., 2017) with an α level of .05 to indicate statistical significance.

Results

Participants at 18 months (n = 26) were 57.7% females. They were 84.6% White, 7.7% African American, and 7.7% Asian American. The largest portion of the sample had mothers with graduate degrees (46.2%). At 24 months (n = 16), participants were 37.5% females. They were 50% White, 18.8% African American, and 31.3% Asian American. Again, the largest portion of the sample had a mother with a graduate degree (62.5%). Ponderal indices of each group increased from the 18-month-old group to the 24-month-old group (2.7 at 18 months and 3.22 at 24 months). At 18 months, participants wore the accelerometer an average of 5.5 days, at 513.8 minutes per day. At 24 months, participants wore the accelerometer for an average of 6.6 days at 490.3 minutes per day. Table 1 presents descriptive information of the sample.

At 18 months, average Gross, Fine, and Total motor raw scores were 49.2, 36.6, and 85.7, respectively. At 24 months, participants’ raw scores were higher at 56.2, 38.8, and 94.9, respectively. At 18 months, participants spent an average of 313 minutes per day in sedentary activity. At 24 months, they spent an average of 394.5 minutes per day in sedentary activity.

In both age groups, gross motor ability, but not fine motor ability, inversely correlated at a significant level with time in sedentary activity. At 18 months, gross motor raw score inversely correlated with time in sedentary activity (r = −.533, p < .001), but fine motor raw score did not (r = .182, p = .441). At 24 months, gross motor raw score also inversely correlated with time in sedentary activity (r = −.563, p = .029), but fine motor raw score did not (r = −.112, p = .425). The aforementioned relationships are presented in Table 2 and presented graphically in Figure 1 as scatter plots.

Figure 1.

Scatterplot representations of associations between motor skill raw scores and sedentary PA per day at (a) 18 months and (b) 24 months.

Table 2.

Bivariate Correlations Between Motor Skill and Accelerometry Variables at 18 and 24 Months.

	Gross motor		Fine motor		Total motor
	r	p	r	p	r	p
18 months
Sedentary PA	−.533	<.001	.182	.441	−.343	.139
Light PA	−.501	.024	.258	.272	−.266	.258
Moderate PA	.005	.984	.138	.562	.094	.693
24 months
Sedentary PA	−.563	.029	−.112	.425	−.363	.184
Light PA	−.395	.146	−.119	.673	−.229	.413
Moderate PA	−.377	.166	−.020	.945	−.153	.587

Note. r = Pearson correlation coefficient; p = significance level; PA = physical activity.

Discussion

This study demonstrated an inverse relationship between gross motor development and daily sedentary time in two groups of infants aged 18 months and 24 months. This study also demonstrated no relationship between motor development and daily moderate activity. These findings are in contrast with previous studies where preschool-aged children demonstrated a strong relationship between gross motor development and Moderate – to – Vigorous intensity Physical Activity (Williams et al., 2008). Thus, it may be that the connection between moderate physical activity and gross motor development strengthens after 24 months of age. In addition, we found no relationships between fine motor development and activity variables at either 18 or 24 months of age. These results are similar to several studies on prone positioning, showing that prone positioning increases activity and does not improve fine motor skills but does influence a number of important gross motor milestones (Dudek-Shriber & Zelazny, 2007; Kuo, Liao, Chen, Hsieh, & Hwang, 2008; Wentz, 2017).

It has been speculated that children develop sedentary habits prior to five years of age (Jones et al., 2013). There is evidence that sedentary activity habits track in individuals over time, tracking coefficients for a given individual (from <5.9 years to 6–18 years) show a median of .52 (large effect) for sedentary behavior, compared with .36 (medium effect) for physical activity (Biddle, Pearson, Ross, & Braithwaite, 2010; Janz, Burns, & Levy, 2005; Janz, Dawson, & Mahoney, 2000; Jones et al., 2013; Pate et al., 1999). In addition, certain sedentary behaviors, such as television or video game use, may be more heavily entrenched than active behaviors (Epstein, Smith, Vara, & Rodefer, 1991). Thus, the infant period may deserve attention for constructing interventions specific to increasing motor performance. Infancy is a period of inherent plasticity in which habits are potentially modifiable (D. A. Ulrich & Hauck, 2013). Indeed, recent studies in children of preschool age show several important correlates of reduced sedentary time in preschools, including increased child-initiated interactions, increased free play area, mixing different age groups together, and most importantly, having a written physical activity policy (Arhab et al., 2018). In addition, in a longitudinal sample of 1-6-month-old infants, average time spent in constraining infant devices ranged from 4.2 to 8.7 hours during a 24-hour observational period; guidelines might also address constraining devices (Hauck, 2012). These promising findings suggest concrete modifications that could be taken in early childhood educational environments to intervene on sedentary behaviors before they are solidified.

In particular, the once recommended policy of eliminating screen time before two years of age (Zimmerman, Christakis, & Meltzoff, 2007) merits attention (Dietz & Strasburger, 1991). This recommendation has been since updated to allow some screen time in infants and toddlers but only when supervised and interactive with a caregiver (Council on Communications and Media, 2016). Recent studies show that children under two years of age likely spend large portions of their day engaged in screen time (Perrin et al., 2014). The motor ramifications of these trends are of great interest, and future research might consider this.

This study has two main limitations. Our findings are from a small sample of children, mostly from a high socioeconomic background meaning that our results should be interpreted with extreme caution regarding their generalization to other samples. Further investigation is necessary to verify these findings. In addition, these findings are observational, and their cross-sectional nature means that no causal conclusions regarding these relationships may be drawn.

Despite these limitations, strengths of this research include an important finding of an inverse correlation between gross motor development and daily sedentary time at 18 and 24 months and its identification of a research knowledge gap, namely, sedentary activity in toddlers, that warrants further investigation.

Footnotes

Article Notes

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