1. What will happen to me if I take part?

All study visits will be at the University of Glasgow main campus within the Sir James Black building.

Initial visit (duration 1 hours)

We will ask that for each study visit you come to the laboratory with clothing suitable to exercise in (loose shorts) for your own comfort and to also make it easier for us to complete certain measurements where access to upper legs will be necessary. Changing facilitates will be provided on-site. After the screening process, your physical activity and your diet will be assessed via questionnaires. We will then familiarise you with the physical function tests and neuromuscular measurements.

Visit 2 (duration 1 hours)

Before the remaining study visits in the morning, you will be asked to arrive at the laboratory after an overnight fast (no food or caffeinated/calorific beverages from 10pm), and without having done intense exercise for two days prior to the visit. Upon arriving in the laboratory, we will collect a blood sample (after which we will provide you with a snack), and measure your body composition, muscle size, muscle strength and physical function. You will then be familiarised with the resistance training protocol, and we will determine your maximum strength for two leg exercises. After these measurements are completed, we will randomly assign you to consumed 2g/day of either krill oil or a mixed vegetable oil.

Visit 3 (duration 3 hours)

After 8 weeks of supplementation, you will attend for a third study visit. This will involve a blood sample and repeating the same measures from the baseline visit with the addition of a measurement of soreness in the upper legs. We will then ask you to complete muscle-damaging exercises consisting of a warm-up of 5 minutes of downhill walking (5% decline at a self selected speed between 3-6 km/h) followed by 4 sets of machine exercises of both leg kicking and leg pushes. These leg exercises will be performed at ~70% of your maximum strength and we will ask you to perform as many repetitions as you can, with the last two sets of each exercise also consisting of 4 extra lowering repetitions. Five minutes and 60 minutes following the muscle-damaging exercise, all the measurements, including blood samples, will be repeated.

Visit 4 (duration 1 hours)

Two days after visit 3, we will once again repeat the measures taken on visit 3 for a final time.

Measurements

Blood sample: A blood sample (15ml) will be collected from a vein in your arm by a trained member of the research team.

Muscle size: We will use an ultrasound to assess muscle thickness of one of the muscles on the outside of your legs.

Muscle strength: You will sit in a chair with your legs at a 90-degree angle. A strap will be placed around the right ankle which will be connected to a force sensor and three sticky surface electrodes will be placed on your thigh. We will then ask you to contract as hard as you can with the leg fixed in position, and we will record the force for 5 seconds. You will perform 3 contractions, with a 1min rest between contractions. After the maximal contractions, will be ask you to contract at 20, 35 and 50% of your maximal effort for 15 seconds so that we can record electrical activity in your muscle. We will then stimulate a contraction with a small electrical current at rest and during a maximal contraction.

We will also measure grip strength, making 3 measures from each hand. We will measure your strength on exercise machines, for both leg kicking and leg pushing. Following a warm-up, the weights on each machine will be progressively increased in until you cannot do any more.

Physical function: We will ask you to rise from a chair 5 times and to walk a distance of 4 metres and record how long this takes. We will also ask you to stand for 10 seconds with your legs in 3 different positions. These will be demonstrated to you before you do this.

Body composition: We will measure total fat and lean mass using bioelectrical impedance analysis.

Soreness: We will ask you to mark on a line how sore your muscle feels to measure muscle soreness before and immediately after the muscle damage protocol in two different tests. In the first test, we will apply a fixed, moderate amount of pressure on your thigh and we will ask you how sore it feels; in the second test, we will apply an increasing amount of pressure until on your thigh until you tell us it feels sore.

Inclusion Criteria:

• Be 60 years old or older
• Have a BMI of less than 30kg/m2
• Participating in resistance-type exercise for less than 1h per week

Exclusion Criteria:

• Diabetes
• Severe cardiovascular disease defined as arrythmia, valve disease, coronary artery disease, heart failure, peripheral arterial disease, cerebrovascular disease, congenital heart disease or myocardial infarct.
• Seizure disorders
• Uncontrolled hypertension (blood pressure higher than 150/90mmHg at baseline measurement)
• Cancer or cancer that has been in remission for less than 5 years
• Ambulatory impairments limiting the ability to perform muscle function assessments
• Dementia
• Taking medications known to affect muscle (like steroids)
• Having an implanted electronic device (such as a pacemaker, defibrillator, or insulin pump)
• Allergies to seafood
• Regular consumption of more than one portion of oily fish per week