Table 2: Objectively measured physical activity at baseline and follow-up periods across grade cohorts and total study sample.

Grade 9 ( )Grade 10 ( )Total ( ) value
% % %

Students with valid PA at each time point
 T0: Prepolicy296(100.0)151(100.0)477(100.0)N.A.
 T1: February 2009–June 200999(33.4)68(45.0)167(37.4)N.A.
 T2: September 2009–January 201073(24.7)21(13.9)94(21.0)N.A.
 T3: February 2010–June 2010138(46.6)94(62.3)232(51.9)N.A.
 T4: September 2010–January 201154(18.2)0(0.0)54(12.1)N.A.
 T5: February 2011–June 2011122(41.2)2(0.0)124(27.7)N.A.
 T6: September 2011–December 201144(14.9)0(0.0)44(0.09)N.A.

Time points contributed per student, mean ± SD2.79±1.182.23±0.8502.60±1.11<0.0001a

Baseline PA
 Students with baseline data296(100.0)151(100.0)447(100.0)N.A.
 Minutes per day, mean ± SD58.7±24.157.6±23.858.3±24.00.5890a
 Accumulated ≥ 30 min/day265(89.5)131(86.8)396(88.6)0.3833b
 Accumulated ≥ 60 min/day138(46.6)61(40.4)199(44.5)0.2104b

PA at students’ last followup
 Students with ≥ 1 followup230(77.7)110(72.9)340(76.1)0.3304b
 Minutes per day, mean ± SD42.6±23.547.2±23.944.1±23.70.0485a
 Accumulated ≥ 30 min/day (% with ≥ 1 followup)149(64.8)82(74.6)231(67.9)0.0712b
 Accumulated ≥ 60 min/day (% with ≥ 1 followup)46(20.0)25(22.7)71(20.9)0.5627b

PA change from baseline to last followup
 Students with ≥ 1 followup230(77.7)110(72.9)340(76.1)0.3304b
 Change (min/day), mean ± SD−14.6±24.7−11.1±29.0−13.4±26.20.2701a
 Percentage change (%), mean ± SD−18.7±48.8−10.0±51.0−15.9±49.60.1871a

Wilcoxon two-sample test used to compare across grade cohorts.
bChi-square test used to compare across grade cohorts.
N.A.: denotes not applicable.