Date of Award
2024
Document Type
Thesis
Publisher
Edith Cowan University
Degree Name
Doctor of Philosophy
School
School of Medical and Health Sciences
First Supervisor
Anthony Blazevich
Second Supervisor
Janet Taylor
Abstract
There is growing interest in abbreviated pre-exercise warm-up protocols, sometimes called conditioning activities (CAs), which involve the performance of relatively few intense muscle contractions with the aim of improving muscle contractile function. However, little is known about the specific mechanisms underpinning CA-induced performance enhancements, and studies involving heavy-load CAs often report a delayed performance enhancement due to post-CA “fatigue” but which possibly instead reflects a motor pattern interference effect. The primary aims of the present research were to (i) review (with meta-analysis) the literature in relation to the effects of muscle temperature (Tm) on muscle contractile function, (ii) explore the mechanisms underpinning CA-induced performance improvements, and (iii) describe the acute corticospinal adaptations to a non-velocity-specific CA to better understand potential motor pattern interference effects.
In Study 1, a systematic review with meta-analysis revealed that Tm elevation enhances explosive muscle strength (ES=0.28-0.65) but not maximum muscle strength (ES=-0.20-0.08) in both evoked and voluntary contractions. Factors such as active vs. passive warm-up, study design (pre-to-post comparison vs. post-intervention data only vs. no control group), temperature measurement site (skin vs. muscle), warm up-test-exercise specificity, training status, and biological sex did not influence the results (p > 0.05).
In Study 2, task-specific practice increased peak isokinetic knee extensor torque at 180°×s-1 (T180) by 13%. Subsequent performance of five slow-speed knee extensions (CAslow) immediately decreased T180 by 10%, whereas 15 fast-speed contractions (CAfast) further increased T180 by 5% above task-practice levels. Tm changes (r=0.29-0.63) and M-wave normalised initial electromyogram burst amplitude (i.e. first 40 ms, EMG40ms/M) were correlated (r=0.37-0.41) with changes in T180 across post-CA time points. However, the strongest correlation across time points was observed when Tm and EMG40ms/M were combined (r=0.67-0.69). Peak twitch torque was moderately correlated with T180 only in CAfast (r=0.31).
In Study 3, both CAfast and CAslow increased total thigh muscle water (TW) at 1 min post-CA by 3%, largely as a result of intracellular water accumulation (ICW, +3%; TW vs. ICW: r=0.94-0.97). Extracellular water increase was delayed (+2-3%, 5-13 min post-CA). The T180 increase (+12%) was moderately correlated with both TW and ICW increases (r=0.34- 0.43), suggesting a possible role of TW or ICW in the performance enhancement effect.
In Study 4, CAslow reduced initial electromyogram burst amplitude (i.e. first 40 ms, EMG40ms) by 30% and preparatory-phase motor evoked potential amplitude (MEPPREP) by 38% when measured during high-speed knee extensions, indicating a reduced corticospinal excitability, while CAfast induced non-significant mean increases of 23% and 40%, respectively (both significantly greater at post-CA than CAslow).
Therefore, Tm and, potentially, muscle water increases with warm-up contribute favourably to performance enhancements, but only when muscle activation is optimised. Muscle activity, especially in the initial phase, is a strong mediating variable that affects normal relationships between Tm, muscle water, and explosive muscle function. Additionally, decreases in rapid muscle activation following a non-velocity-specific CA (CAslow) were accompanied by reduced corticospinal excitability during the preparatory phase of the contraction, suggesting a motor pattern interference effect. Finally, “classic” PAP appears to play a minor role, at most, in voluntary muscle function enhancements. The present findings indicate that muscle activation optimisation through task-specific warm-up exercises may be crucial for maximising the advantages of increased Tm and muscle water for enhanced explosive muscle function with abbreviated warm-ups (CAs).
DOI
10.25958/jzy7-ee09
Access Note
Access to this thesis is embargoed until 21 June 2027
Recommended Citation
Wilson, C. (2024). The acute effect of brief, intense muscle warm-up contractions on muscle temperature, muscle water, neural drive and explosive knee extensor muscle function. Edith Cowan University. https://doi.org/10.25958/jzy7-ee09