European Journal of Applied Physiology

, Volume 116, Issue 6, pp 1159–1177 | Cite as

Anatomical and neuromuscular variables strongly predict maximum knee extension torque in healthy men

Original Article

Abstract

Purpose

This study examined the relative influence of anatomical and neuromuscular variables on maximal isometric and concentric knee extensor torque and provided a comparative dataset for healthy young males.

Methods

Quadriceps cross-sectional area (CSA) and fascicle length (lf) and angle (θf) from the four quadriceps components; agonist (EMG:M) and antagonist muscle activity, and percent voluntary activation (%VA); patellar tendon moment arm distance (MA) and maximal voluntary isometric and concentric (60° s−1) torques, were measured in 56 men. Linear regression models predicting maximum torque were ranked using Akaike’s Information Criterion (AICc), and Pearson’s correlation coefficients assessed relationships between variables.

Results

The best-fit models explained up to 72 % of the variance in maximal voluntary knee extension torque. The combination of ‘CSA + θf + EMG:M + %VA’ best predicted maximum isometric torque (R2 = 72 %, AICc weight = 0.38) and ‘CSA + θf + MA’ (R2 = 65 %, AICc weight = 0.21) best predicted maximum concentric torque.

Conclusion

Proximal quadriceps CSA was included in all models rather than the traditionally used mid-muscle CSA. Fascicle angle appeared consistently in all models despite its weak correlation with maximum torque in isolation, emphasising the importance of examining interactions among variables. While muscle activity was important for torque prediction in both contraction modes, MA only strongly influenced maximal concentric torque. These models identify the main sources of inter-individual differences strongly influencing maximal knee extension torque production in healthy men. The comparative dataset allows the identification of potential variables to target (i.e. weaknesses) in individuals.

Keywords

Cross-sectional area Fascicle angle Muscle activity Moment arm distance Linear models Strength 

Abbreviations

AIC

Akaike’s information criterion (an information-theoretic approach for model selection)

AICc

Akaike’s information criterion for a small dataset

ΔAICc

The model's AICc minus the minimum AICc among candidate models

AICcwi

The percentage of times that a given model would be selected as the ‘best-fit model’ by AICc, and serves as the weight of evidence for a given model being the best model from a set of candidate models

BF

Biceps femoris

CI

Confidence interval

CSA

Anatomical cross-sectional area

CV

Coefficients of variation

DIST

Distal region muscle measurements

EMG

Electromyogram

EMG:M

Quadriceps EMG amplitude normalised to M-wave amplitude

EMG:MRF

RF EMG amplitude normalised to RF M-wave amplitude

EMG:MVL

VL EMG amplitude normalised to VL M-wave amplitude

EMG:MVM

VM EMG amplitude normalised to VM M-wave amplitude

EMG:MAVEQ

Average EMG:M ratio of RF, VL and VM

ICR

Instantaneous centre of rotation

ICC

Intra-class correlation coefficient

lf

Fascicle length

MA

Patellar tendon moment arm distance

Mmax

Maximum peak-to-peak amplitude of the M-wave

MVC

Maximal voluntary contraction

MID

Middle region muscle measurements

M-wave

Maximum muscle compound action potential of vastus lateralis

PCSA

Physiological cross-sectional area

PROX

Proximal region muscle measurements

RF

Rectus femoris

RMS

Root mean square

ROM

Range of motion

TCON

Maximum voluntary concentric torque

TCON-QUAD

Maximum quadriceps-only concentric torque

TISO

Maximum voluntary isometric torque

TISO-QUAD

Maximum quadriceps-only isometric torque

TPot-TW

Maximum potentiated twitch torque

TUn-TW

Maximum unpotentiated twitch torque

%VA

Percent voluntary activation (calculated by interpolated twitch technique)

VI

Vastus intermedius

VL

Vastus lateralis

VM

Vastus medialis

θf

Fascicle angle

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Copyright information

© Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  1. 1.Centre of Exercise and Health ScienceEdith Cowan UniversityJoondalupAustralia
  2. 2.Faculty of SustainabilityLeuphana UniversityLüneburgGermany
  3. 3.School of Exercise and Health Sciences, Centre for Exercise and Sport Science Research (CESSR)Edith Cowan UniversityJoondalupAustralia

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