Characterizing objective and self-report habitual physical activity and sedentary time in outpatients with an acquired brain injury

Outpatients with an acquired brain injury(ABI)experience physical,mental,and social deficits.ABI can be classified into two subgroups based on mechanism of injury:mild traumatic brain injury(mTBI;e.g.,concussion)and other ABI(e.g.,stroke,brain aneurysm,encephalitis).Our understanding of habitual activity levels within ABI populations is limited because they are often collected using self-report measures.The purpose of this study was to,1)describe the habitual activity levels of outpatients with ABI using objective and self-report monitoring,and 2)compare the activity levels of outpatients with mTBI vs.other ABI.Sixteen outpatients with other ABI(mean±standard deviation:[58±13]years,9 females)and 12 outpatients with mTBI([48±11]years,9 females)wore a thigh-worn activPAL 24 h/day(h/day)for 7-days.Outpatients with ABI averaged(6.0±2.3)h/day of upright time,(10.6±2.2)h/day of sedentary time,(5.6±2.7)h/day in prolonged sedentary bouts>1 h,(5960±3037)steps/day,and(11±13)minutes/day(min/day)of moderate-vigorous physical activity(MVPA).There were no differences between activPAL-derived upright,sedentary,prolonged sedentary time,and physical activity between the mTBI and other ABI groups(all,p>0.31).Outpatients with ABI overestimated their MVPA levels(t138 min/week)and underestimated sedentary time(-4.3 h/day)compared to self-report(all,p<0.001).Despite self-reporting high activity levels,outpatients with ABI objectively exhibit highly inactive and sedentary lifestyles.The habitual movement behaviours of our sample did not differ by mechanism of injury(i.e.,mTBI versus other ABI).Targeting reductions in objectively measured sedentary time are needed to progressively improve the habitual movement behaviours of outpatients with ABI.

Habitual sedentary time and stationary time are inversely related to aerobic fitness

A one metabolic-equivalent-of-task increase in peak aerobic fitness(peak MET)is associated with a clinically relevant improvement in survival risk and all-cause mortality.The co-dependent impact of free-living physical behaviours on aerobic fitness are poorly understood.The purpose of this study was to investigate the impact of theoretically re-allocating time spent in physical behaviours on aerobic fitness.We hypothesized that substituting sedentary time with any physical activity(at any intensity)would be associated with a predicted improvement in aerobic fitness.Peak volume rate of oxygen uptake(VO_(2)peak)was assessed via indirect calorimetry during a progressive,maximal cycle ergometer protocol in 103 adults(52 females;[38±21]years;[25.0±3.8]kg/m^(2);VO_(2)peak:[35.4±11.5]ml⋅kg^(-1)⋅min^(-1)).Habitual sedentary time,standing time,light-(LPA),moderate-(MPA),and vigorous-physical activity(VPA)were assessed 24-h/day via thigh-worn inclinometry for up to one week(average:[6.3±0.9]days).Isotemporal substitution modelling examined the impact of replacing one physical behaviour with another.Sedentary time(β=0.8,95%CI:[-1.3,-0.2])and standing time(β=0.9,95%CI:[-1.6,-0.2])were negatively associated with VO_(2)peak,whereas VPA was positively associated with relative VO_(2)peak(β=9.2,95%CI:[0.9,17.6]).Substituting 30-min/day of VPA with any other behaviour was associated with a 2.4–3.4 higher peak MET.Higher standing time was associated with a lower aerobic fitness.As little as 10-min/day of VPA predicted a clinically relevant 0.8–1.1 peak MET increase.Theoretically,replacing any time with relatively small amounts of VPA is associated with improvements in aerobic fitness.