Nutritional strategies, including supplementation, are widely sought after to improve the
function of the neuromuscular system (muscle strength and power). Milk fat globule
membrane (MFGM, composed of the membrane that surrounds milk fat droplets) has begun to
receive increasing attention as a potential supplement to improve muscle function and
size due to a series of promising longitudinal studies (> 4 weeks of supplementation),
however the overall findings are still conflicting which is likely due to methodological
limitations of previous studies. Therefore, it is important to thoroughly investigate
whether chronic supplementation of a MFGM-containing supplement is effective at improving
the function and physiology of the neuromuscular system within healthy, recreationally
active adults.
This study aims to compare the effects of chronic (12 weeks) bioactive whey protein
concentrate (BWPC) supplementation versus an isocaloric, isonitrogenous whey protein
isolate placebo on the physiology (contractile properties, coactivation, timing of action
potentials), morphology (total/functional muscle cross-sectional area/volume), and
function of the neuromuscular system of healthy, recreationally active adults.
Utilising a randomised, double-blind, parallel group study design, participants will be
allocated to one of two groups: BWPC or placebo supplement group. Once consented,
participants will complete screening questionnaires to confirm their eligibility.
Altogether, participants will be required to attend 5 laboratory sessions (1
familiarisation ~ 1.5 hours, 4 main measurement sessions each ~ 2 hours) at the
neuromuscular laboratories situated within the Matthew Arnold building at Loughborough
University. The familiarisation and first two baseline measurement sessions will be done
over a 2-week period, after which participants will be asked to consume a supplement
daily for 12 weeks (84 daily doses) while they maintain their usual lifestyle (diet and
exercise/physical activity). Then they will attend two further post measurement sessions,
with the first being at exactly 12 weeks of supplementation (i.e. 84th day) and the
second being 3-4 days later (i.e. 87th or 88th day). The supplementation protocol will
involve participants mixing 1 scoop of supplement with water and consuming the resultant
drink alongside their breakfast. Participants will be required to fill in a diet record
form twice across the supplementation period (week 3 and 9), which involves weighing and
recording what they eat/drink over 3 consecutive days. Physical activity at pre and post
will be assessed through the International Physical Activity Questionnaire (IPAQ, short
format).
During the familiarisation session participants will get to try all of the types of
contractions (voluntary and involuntary) to be performed in the main measurement
sessions, but without the recording of electromyography (EMG). The first measurement
session at baseline/post will begin with countermovement jumps on a force plate. The
remainder of the session will involve various isometric knee extension or flexion
contractions within a custom-built isometric dynamometer. This will include maximal and
explosive voluntary contractions to assess maximal strength of the knee extensors and
flexors and rate of force development of the knee extensors, respectively. Supramaximal
femoral nerve stimulation will be utilised to evoke twitch contractions of the knee
extensors. Submaximal transcutaneous muscle stimulation will be performed to assess the
force-frequency relationship (1 - 100 Hz) of the knee extensors. Finally, submaximal knee
extension contractions (10 and 25% of maximal voluntary force) will be performed while a
concentric needle electrode is inserted into the vastus lateralis to assess the stability
of neuromuscular junction transmission. Throughout this measurement session, surface EMG
signals will be collected by placing surface EMG electrodes on each of the 3 superficial
quadriceps muscles (rectus femoris, vastus lateralis and medialis) and on the hamstrings
(medial and lateral).
Within the second measurement session at pre/post, participant's will have an 3.0 T MRI
scan of the lower limbs. The procedure will be clearly explained to the participant
before they sign the MRI agreement form and fill in the MRI safety questionnaire.
For this study we want to assess whether any potential benefits of milk fat globule
membrane are influenced by age. Therefore, we will be recruiting 2 subgroups (young 18 -
30 years old; older 60 - 75 years old). The power analysis was based on detecting a group
by time interaction for isometric strength, with input parameters of: effect size = 0.15,
alpha = 0.05, power = 0.8, correlation among repeated measures = 0.8. Altogether, 38
participants are needed as a minimum within each age group (19 per group). However, to
account for a 25% drop-out rate, 48 participants will be recruited for each age group.
The total number of participants recruited will be 96 (48 young, 48 older).
Statistical analysis will involve fitting linear mixed effect models to detect any main
effects or interactions, with supplement group, time (pre vs post), and their interaction
as fixed effects, and participant as a random intercept. Visual plots (histograms and
quantile-quantile plots) will be used to verify the assumptions of normality, linearity,
and homoscedasticity of residuals.