Resistance exercise and artery function

The interventions for the current study are moderate intensity resistance exercise (RE) and Valsalva manoeuvres (described below). The current study is separated into 4 visits that are designed to test the physiological responses to RE, Valsalva manoeuvres (VM), and a combination of both. Each participant will complete all 4 visits (no separate arms), and at no point will the participant or researchers be blinded to the requirements of that visit. The first visit is a familiarisation and screening session, designed to determine the eligibility of a participant, answer any questions the participant may have, gain consent from the participant, and familiarise the participant with all study procedures. The following 3 visits will be completed in a randomised order and are designed to determine the effect of the interventions individually, and in combination. However, for simplicity the visits are ordered to indicate the different requirements and are labelled as follows: • Visit 2 – RE only • Visit 3 – RE and VM • Visit 4 – VM only For each visit, the main outcomes of interest are the change in the physiological variables (e.g. pulse wave velocity) from pre-intervention (e.g. prior to resistance exercise) to post-intervention (e.g. following resistance exercise) for each participant (a within-subject design). All study 4 visits will occur face-to-face, in a temperature-controlled laboratory, and be conducted a senior researcher with extensive research experience and 20 years of RE experience. The first visit will take ~1 hour and the reaming 3 visits will take ~2 hours. Each visit will be separated by at least 5 days. The information collected will include the following: Demographics (Visit 1) • Date of birth, age, sex • Height and weight • Participant contact details • Current exercise regimen Medical history (Visit 1) • Other medical conditions and medications • Smoking history: smoking status (ex, current, never) • Females: self-reported pregnancy status and menstrual cycle phase All visits • Adverse events • Serious adverse events Weight and height Height will be measured at visit 1 using a stadiometer and weight with electronic weighing scales. Participants will take off their shoes for both measurements. Pulse wave velocity (PWV) Carotid-femoral PWV will be measured using a high-fidelity tonometer (SphygmoCor, AtCor Medical). The measurement of PWV requires a concurrent electrocardiogram (3 lead) and brachial blood pressure (BP) measurements. The right common carotid and femoral pulses will be palpated. The strongest pulse point for both arteries will be marked, and the straight-line distance from this mark to the suprasternal notch will be measured using a tape measure. The tonometer will then be placed first over the right common carotid artery and be adjusted to obtain the strongest waveform, data will be collected for 10s. The process will be repeated for the femoral artery. Once successful carotid and femoral values have been obtained the Sphygomocor Software Suite (AtCor Medical) will generate an absolute PWV value in m/s. Duplicate measurements will be performed both pre- and post-completion of the visit requirements in visits 2, 3 and 4. If the duplicate measurements differ by >0.5 m/s a third measurement will be performed. All measurements will be completed by the same trained investigator. Middle cerebral artery blood velocity Middle cerebral artery blood velocity (MCAv) will be measured using transcranial Doppler Ultrasonography (Doppler-BoxX, DWL Compumedics) as a proxy for cerebral blood flow. Bilateral middle cerebral arteries will be insonated for the purposes of assessing cerebrovascular function. Dynamic cerebral autoregulation (dCA) Dynamic cerebral autoregulation (dCA) will be assessed using squat-stand manoeuvres (SSM). To quantify dCA continuous (beat-to-beat) measurements of BP and MCAv are required. Non-invasive beat-to-beat measurement of BP will be recorded via finger photoplethysmography (Human NIBP NANO, ADInstruments) and MCAv will be measured as described above. dCA measurements will be performed both pre- and post-completion (immediately after PWV measures in each instance) of the visit requirements in visits 2, 3 and 4. For the SSM, each participant will complete 2 bouts of SSM generating BP oscillations at 2 distinct frequencies - 0.05 Hz (20 s cycle: 10 s squat followed by 10 s standing) and 0.10 Hz (10 s cycle: 5 s squat followed by 5 s standing) that are timed by metronome. During the squatting phase each participant will perform a body weight squat (no additional load) until 45 degrees of knee flexion is achieved. The participant will hold this position (for either 5s or 10s), and then stand (for 5s or 10s). The participant will repeat this cyclic manoeuvre at each frequency (0.05 Hz or 0.1 Hz) for 5 minutes, with each bout of SSM separated by 5 minutes of seated rest. Additionally, heart rate will be measured via three lead electrocardiogram and partial pressure of end tidal carbon dioxide will be measured via nasal cannula to account for the influence of arterial carbon dioxide content on cerebral blood flow. Valsalva Manoeuvre (VM) All VMs completed in the current study will have a target mouth pressure (intensity) of 40 mm Hg. During the familiarisation session and visit 4 participants will be asked to blow into a cardboard mouthpiece that is connected to a calibrated pressure transducer with the achieved pressure displayed to the participant in real-time. The VMs that do not meet the target pressure will still be counted and contribute to the overall total. In visit 3 where RE will be performed with a VM, the VM will be performed during the concentric phase only during the last 6 repetitions of each set, for all exercises (see below). During visit 4 (VM only) participants will complete a total of 72 VMs performed across 12 ‘sets’. Each set will consist of 6 short VMs of 3s, separated by 2s breaks. The timing of the VM and breaks will be given verbally by the research team. Each set of VMs will be separated by 3 minutes of rest. The total number of VMs performed during visits 3 and 4 is matched at 72 and will be counted by the research team. Resistance Exercise (RE) The exercise loading for this study is 60% of the estimated 1 repetition maximum (1RM). The estimation of the 1RM for bicep curl, leg extension, leg press, and chest press will be completed within the familiarisation session (visit 1). Using the number of repetitions completed, and the load lifted, the 1RM can be estimated using Brzycki’s equation. During the determination of the 1RM for each exercise, the participant will complete sets of <10 repetitions of a self-selected submaximal load. The load will then be increased gradually across multiple sets such that the participant fatigues prior to completing 10 repetitions. Each set and exercise will be separated by 3 minutes of recovery time. During visits 2 and 3, participants will complete 3 sets of 10 repetitions for bicep curl, leg extension, leg press, and chest press at 60% of the 1RM value achieved in visit 1 (60%1RM). Each set will be separated by 3 minutes of rest. All sets and reps will be counted by the research tea. The bicep curl exercise will be completed first using a dumbbell whilst seated. The remaining exercises will be completed in a random order using Life Fitness exercise machines that will be adjusted to fit the participant. The breathing techniques (e.g. VM or continued ventilation) for each session where RE is performed is outlined below. Participants will be coached in the familiarisation session, and verbally instructed/reminded of the breathing requirements and exercise technique during visits 2 and 3. Visit 2 – RE only During this session: • Participants will perform 3 sets of 10 repetitions of bicep curl, leg press, leg extension and chest press at 60%1RM. Each repetition will be timed to a metronome, with 2s for both the eccentric and concentric phases (4s per repetition). The participant will be asked to exhale during the eccentric phase of the movement and inhale during the concentric phase. Visit 3 – RE and VM During this session: • Participants will perform 3 sets of 10 repetitions of bicep curl, leg press, leg extension and chest press at 60%1RM. Each RE repetition will be timed to a metronome, with 2s for both the eccentric and concentric phases (4s per repetition). The participant will be asked to exhale during the eccentric phase of the movement and inhale during the concentric phase. During the last 6 repetitions of each set the participant will be verbally instructed to perform a VM during the concentric phase of each exercise, generating a mouth pressure of ~40 mm Hg (no real-time feedback i.e. estimated). Participant information and education Resistance exercise technique All resistance exercise will be first demonstrated to the participants in visit 1 a senior researcher with 20 years of resistance training experience. Following the demonstration of the correct technique, the participants will be able to practice the movements without additional load prior to the estimation of their 1RM. Only when correct technique is demonstrated will additional load be applied. Feedback regarding exercise technique will be provided throughout all visits by the investigators, and all RE will be supervised. The investigators will also be able to assist the participant should they fatigue and be unable to lift the load during any visit. Diet recall Participants will be asked to repeat their diet for the 12 hours prior to visit 2, 3 and 4. As visits 2, 3 and 4 are randomised, the participant will be asked to keep a diet diary for the 12 hours prior to whichever of visits 2, 3 and 4 occurs first, and then repeat this diet prior to remaining visits. Participants will be provided with a food recall diary at visit 1 and a list of vasoactive foods that should be avoided prior to each visit. Adherence to the diet requirements will be self-reported. The diet diary will be returned at the final study visit. Restrictions prior to all visits: • Strenuous exercise and alcohol for 12 hours, and caffeine (e.g. coffee, tea, or energy drinks) for 4 hours, prior to arriving at the laboratory. Foods to avoid 12 hours prior to your laboratory visit: • Beetroot and beetroot juice • Dark chocolate • Berries including blackcurrants and grapes • Nutritional supplements containing high nitrate or anthocyanin content