Table 2 Outcome measures and psychometric properties

Body structures and functions

Muscle endurance

Six-Minute Bicycle Test*

Feasible for ambulant and non-ambulant boys with DMD (pilot study, unpublished data)

T0, T2, T5

Joint mobility (PROM)

Goniometry[55] (knee ext*, ankle dfl*, shoulder abd*▪, elbow ext*▪, wrist ext▪, wrist radial and ulnar dev▪)

Standardized methods are feasible[56] and have good intra- and inter-rater reliability in DMD[57]

Passive wrist radial deviation is correlated with functional hand activities[58] and lower extremity contractures are related to onset of wheelchair reliance in DMD[4]

All

Muscle strength

Modified MRC[59] (hip ext*, knee ext* ankle dfl*, shoulder abd*▪, elbow ext*▪, wrist ext▪)

Moderate to good intra-rater reliability[59] and acceptable inter-rater reliability in DMD after a training session[60]

Muscles with MRC grade 4 or 5 are difficult to measure with MMT, but muscles with MRC grade ≤3 are more difficult to measure with HHD[4]

All

Muscle atrophy, intra-muscular fibrosis and fatty infiltration

Quantitative skeletal muscle ultrasonography (muscle thickness and echo intensity) [61]: RF, TA, BB, FF*▪

Good inter-rater agreement in children[62]

High predictive values to discriminate between children with and without a NMD[63]

T2, T5, T6/T7*

Bone density

Dexascan (femur and lumbar spine)*

Changes in bone mineral density can be detected with confidence in healthy boys ≥10 years after 6 months and in younger boys after 12 months[64], but a change in body shape may influence scan results[65]

Conventional protocol for each boy

Incidence of fractures

Semi-structured interview*

All

Activities

Functional abilities

Motor Function Measure[37] (D1*, D2*, D3*▪)

Excellent internal consistency for the global scale and the subscales in NMD[37]

Excellent to moderate intra- and inter-rater reliability in NMD[37]

Good face validity, convergent validity and discriminant validity in NMD[37]

Sufficiently sensitive to detect changes in the total score in DMD[66]

Total score predicts loss of ambulation in DMD[67]

All

Upper limb function

Action Research Arm Test[40, 41] ▪

Excellent intra-rater, inter-rater and test-retest reliability in stroke patients[40, 41]

Highly correlated with the Fugl-Meyer score⁴⁷ and Functional Independence Measure⁴⁸ in stroke patients

Suitable to detect changes over time in stroke patients[42]

All

Functional abilities (grading)

Vignos* and Brooke Scale*▪ [56]

Good inter-rater and intra-rater reliability[57, 57] and correlated with timed tests[46, 68, 69] in DMD

All

Functional mobility

Functional Mobility Scale[70] *

A clinically feasible, valid and reliable tool in CP[70, 71]

All

Functional abilities (timed tests)

Timed and graded functional tests (and total GSGC score) [72]: walk 10 meters, climb 3 stairs, rise from the floor and rise from a chair*

Good to excellent intra- and inter-rater reliability in DMD[57, 73]

Sensitive to change in DMD: a small reduction in muscle force was accompanied by a large increase in time it takes to complete functional tests[74]

All (gait, stairs and chair only in the hospital)

Finger dexterity

Nine-hole Peg Test[75] *▪

Moderately high test-retest reliability, high inter-rater agreement and adequate concurrent validity in school-age children[76]

All

Hand function

Jebsen-Taylor Hand Function Test[77] ▪

Good test-retest reliability in DMD[58]

Strongly correlated with muscle strength of the wrist extensors[58], radial deviation range of motion[58] and the Brooke scale[46] in DMD

T2, T4, T5

Functional status

PEDI[78, 79] (selfcare*▪ and mobility*)

Good inter-rater and test-retest reliability[80], content validity[79] and discriminative validity[81] in children with various diagnosis

Feasible for evaluative purposes in CP[81, 82]

T0, T2, T4, T6/T7*

Perceived manual abilities

Abilhand[83] ▪ Abilhand-kids[84] *

The Rasch-derived Abilhand is moderately related to grip and key pinch strength, has good test-retest reliability and may be sensitive to change in stroke patients[85]

The Abilhand-kids has good test-retest reliability and a higher independence in gross motor function is associated with a higher manual ability in CP[84]

T0, T2, T4, T6/T7*

Quality of upper-limb motor function

Melbourne Assessment of Unilateral Upper Limb Function[86] (item 1,2,3,10,11 and16) extended with an upper limb motion analysis (Vicon Motion Systems) with 8 cameras▪

The Melbourne Assessment has moderate to high intra- and inter-rater reliability[87] and excellent construct validity in CP[88]

A motion capture analysis system can measure task performance with an upper-limb orthosis[45], but soft tissue artefacts may negatively influence accuracy[49]

T2, T4

Incidence and fear of falls

Semi-structured interview*

All

Participation

HRQoL

KIDSCREEN-52[89](child- and parental questionnaire)*▪

Acceptable levels of reliability and validity in children and adolescents[90]

Children's most important in their lives generally map well to the items in KIDSCREEN[91]

T0, T2, T4, T6/T7*

Demographic variables

Weight and height

Body weight (kg)*▪, standing height* (cm) and arm-span*▪ (cm)

T0*, T2, T4, Y6/T7*

Co-factors

Co-interventions

Semi-structured interview*▪

All

Physical activity

Semi-structured interview (according to the PAQ-C[92] and the 60-min MVPA measure[93])*▪

All