The Krill Ageing Muscle Mechanisms (KAMM) Study

We will measure grip strength using a handgrip dynamometer, making 3 maximal contractions in each hand, with the dominant hand recorded. The highest grip strength will be used in analysis.

We will assess peripheral motor unit (MU) characteristics in the vastus lateralis muscle using intramuscular electromyography

We will measure gait speed using a gaitrite connected mat during a 4 m walk test and the timed up and go test at usual speed.

We will measure the muscle strength of the knee extensor muscles during a maximal voluntary contraction (MVC)

We will measure this using ultrasound

We will measure this using ultrasound

We will measure this using ultrasound

Blood samples (15 ml each visit) will be collected

During the contractions to measure NMJ transmission instability we will also calculate force steadiness, as a measure of neuromuscular control

will be measured using High Density surface electromyography (HDsEMG) during submaximal (10%, 30%, 50% and 70% of MVC) and during the MVC

Motor unit spike train will be measured using the surface electromyography (sEMG) electrodes while participants exert 20% of maximum voluntary contraction

Intermuscular coherence will be measured for 1 min on 20% of MVC using sEMG electrodes.

Cortico-muscular coherence is a derived measure, based on measurement of the electroencephalography (EEG) and motor unit spikes. EEG electrodes will be placed over the motor area of hands and worn during hand contractions

Single stimuli will be delivered to the muscle while participants maintain a 20% MVC isometric contraction, and the intensity of stimulation was increased until a plateau in twitch amplitude and rectus femoris M-wave (Mmax) occurs. Supramaximal stimulation will then be delivered by increasing the final stimulator output intensity by a further 30%.

Motor evoked potentials (MEPs) will be elicited in the rectus femoris of the dominant leg via single pulse TMS and assessed using electromyographic (EMG) recordings.

corticomotor inhibition during the MVCs a single TMS stimulation will be delivered over the motor cortex.

For assessment of corticospinal excitability, participants will maintain a 20% MVC isometric contraction while 20 single TMS pulses, separated by 6 s, will be delivered over the motor cortex

The 4 m walk test involves participants walking a 4m distance at a normal walking pace, walking through the 4m line at the end of the gaitrite mat. The Timed Up and Go test (timed version of the Get Up and Go test) involves the participant sitting on a chair getting up, walking 3 meters in front of them across the gaitrite mat, returning to the chair and sitting down. The Theia markerless system will be used to extract Gait parameters

We will also get posture information from the 3D skeleton measurements and balance (pitch and roll) which are important in assessing fall risks and functional gait.