Effects of verbal instruction on maximal isometric force and rate of force development in people with multiple sclerosis and healthy controls

TY - JOUR

T1 - Effects of verbal instruction on maximal isometric force and rate of force development in people with multiple sclerosis and healthy controls

AU - Destefano, Natalie

AU - Barone, Donald

AU - de Freitas, Paulo B.

AU - Uygur, Mehmet

N1 - Publisher Copyright: © 2025 DeStefano, Barone, de Freitas and Uygur and BJMB.

PY - 2025/3/15

Y1 - 2025/3/15

N2 - BACKGROUND: Isometric maximum force (MaxF) and rate of force development (MaxRFD) obtained from sustained contractions are two important outcomes used in clinical and research settings that evaluate strength and power of an individual, respectively. These outcomes are often impaired in people with multiple sclerosis (PwMS) and are associated with functional limitations. The values of these isometric outcomes can be influenced by the verbal instructions given to the participants prior to contraction. AIM: We investigated the effects of two common instructions-“as hard as possible” (AH) and “as fast and as hard as possible” (AFH)-on MaxF and MaxRFD in both upper and lower extremities in PwMS and in controls. METHODS: Twenty-seven PwMS (median EDSS=2.0, range: 0-5.5) and age-and gender-matched healthy controls completed isometric assessments of grip force (GF) and knee extension (KE) under both AH and AFH instructions. RESULTS: Instructions did not significantly affect MaxF in either group or muscle group (p>0.05). However, AFH instruction yielded a significantly higher MaxRFD compared to AH in both GF and KE across both groups (p<0.001). INTERPRETATION: MaxF is unaffected by instruction type, while MaxRFD is sensitive to instruction that emphasizes both speed and magnitude of a contraction. Therefore, AFH instruction enables efficient and simultaneous assessment of both outcomes in neuromuscular evaluations, including clinical populations like PwMS where both outcomes may be impaired, and where the effects of disease could be more prevalent in the lower extremity than the upper extremity.

AB - BACKGROUND: Isometric maximum force (MaxF) and rate of force development (MaxRFD) obtained from sustained contractions are two important outcomes used in clinical and research settings that evaluate strength and power of an individual, respectively. These outcomes are often impaired in people with multiple sclerosis (PwMS) and are associated with functional limitations. The values of these isometric outcomes can be influenced by the verbal instructions given to the participants prior to contraction. AIM: We investigated the effects of two common instructions-“as hard as possible” (AH) and “as fast and as hard as possible” (AFH)-on MaxF and MaxRFD in both upper and lower extremities in PwMS and in controls. METHODS: Twenty-seven PwMS (median EDSS=2.0, range: 0-5.5) and age-and gender-matched healthy controls completed isometric assessments of grip force (GF) and knee extension (KE) under both AH and AFH instructions. RESULTS: Instructions did not significantly affect MaxF in either group or muscle group (p>0.05). However, AFH instruction yielded a significantly higher MaxRFD compared to AH in both GF and KE across both groups (p<0.001). INTERPRETATION: MaxF is unaffected by instruction type, while MaxRFD is sensitive to instruction that emphasizes both speed and magnitude of a contraction. Therefore, AFH instruction enables efficient and simultaneous assessment of both outcomes in neuromuscular evaluations, including clinical populations like PwMS where both outcomes may be impaired, and where the effects of disease could be more prevalent in the lower extremity than the upper extremity.

UR - https://www.scopus.com/pages/publications/105031103603

UR - https://www.scopus.com/pages/publications/105031103603#tab=citedBy

U2 - 10.20338/bjmb.v19i1.517

DO - 10.20338/bjmb.v19i1.517

M3 - Article

SN - 1980-5586

VL - 19

JO - Brazilian Journal of Motor Behavior

JF - Brazilian Journal of Motor Behavior

IS - 1

M1 - e517

ER -