Effects of Variable Load Exercise on Aging Atrophy

This study is being conducted to determine whether a novel training approach (variable load exercise) is an effective countermeasure to attenuate for rapid declines in muscle power, function, contractile capacity and fiber type distribution that typically originate from aging and muscle disuse.

The present study is planned over a 24-month investigation period, including ethics application write-up, equipment calibration, participant recruitment, general health examination, familiarization trails, pilot study, data collection in the main portion of the study, data analysis and paper write-up for peer-review journal.Collaboration with Institute for Kinesiology Research of Koper (a municipality in Slovenia), University of Split, University of Udine and Padua is planned. In addition, recruitment of students of Applied Kinesiology at University of Primorska, to collaborate on data collection so they could use data acquired to write their final papers or master thesis is also planned.

After obtaining ethical approval, seniors will be recruited from the Primorska region in Slovenia, via presentations in Daily Activity Centers, social medial and local newspaper. Exclusion and inclusion criteria will be applied as outlined in the next paragraph and those applicants remaining will be randomized into different groups. Data collection will be carried out on eight separate occasions, including familiarization, pilot testing, main portion of the study and follow up data collection, in a randomized counter balance crossover fashion. Following familiarization and pilot study all participants will be randomly assigned to either (I) RT or (II) variable load exercise (VLE) before a crossover of experimental protocols is executed, after a minimum washout period (2x times the duration of experimental protocol) and a follow-up measurement will take place two weeks after experimental protocols are completed. Each participant will be allocated into RT or VLE with pre/post measurements preceding each condition, for eight consecutive weeks following a structured linear periodization model, previously used in healthy older adults (Colon et al., 2017). In total of 2 weeks of familiarization period (to ensure reliability of assessment and avoid learning effects), 4 weeks of pilot study (comparing old and young participants) 16 weeks of different training protocols (RT and VLE, plus 4 weeks of washout period) accompanied with follow-up measurements two weeks after completing training protocols, since training effects are in general dose-dependent and their effects are reversible. Lastly, testing procedures will be conducted at the same facility, by the same researchers using the same equipment at the similar time of the day across the investigation.

The selection of participants will consist of both male and female adults established on a purely voluntary basis. We will follow a strict inclusion and exclusion criteria (in brief):

1. Inclusion criteria: (Signed informed consent and doctor's permission; Age >50 years)
2. Exclusion criteria: (Any cardiovascular disease or ECG examination abnormalities (at rest and under load); hypertension (resting BP > 140/90 mm Hg); previous history of musculoskeletal and neurological disorder/injury; previous history of neurological disorders; supplement or drug consumption that may interfere with training outcomes; alcohol consumption and smoking; BMI >30 kg/m2).

The risks and benefits will be outlined to each participant before inclusion into the study. Risks include potential transient discomfort from the venipuncture blood sampling and muscle soreness originating from experimental training protocols. The participants will get valuable information on how their muscles adapt following systematic training protocols.

Experimental Protocol (Total experimental time: ~120 min for all trails, pre/post data collection):

1. Arrival to laboratory, anthropometric characteristics assessment; resting BP measurement
2. Rest, supine 30 min; complete blood sampling to measure inflammation response;
3. Perform non-invasive muscle composition assessment with Tensiomyography (TMG) of lower limbs;
4. Perform high density surface electromyography (HD EMG) of vastus lateralis and medialis muscles;
5. Perform muscle architecture assessment by ultrasound imaging;
6. Perform muscle voluntary contractions using dynamometry .
7. Energy cost of locomotion assessment

In order to increase the accuracy of the results of the study, all individuals will participate in a two session familiarization period before the study began. The subjects were asked to withdraw from intense physical activity two days prior to baseline assessment. All assessments will be performed in a closed and ventilated facility, with a temperature range of 18-22 C during the morning, and by the same researchers.

Intervention: To determine the optimal load during a single training session of multiple joint squat exercise by using the flywheel (FW) device (http://nhance.se/products/nhance-squat-ultimate/). A large number of papers were published in this area demonstrating that this sort of eccentric muscle overload is beneficial in terms of muscle power gains, balance improvements, contractile capacity, early architecture changes etc., in aging population. The key advantage of this sort of exercise (compared to classical RT) is that this device is equipped with three different wheels, providing different inertia (load), corresponding to 0.025, 0.05, 0.1 kg m2. Even more, this device offers an actual power output feedback (in Watts) in real-time. Thus, this allows us to benchmark a certain threshold where actual changes in both neuromuscular and cardiovascular system(s) occur (in case of continuous BP monitoring, of course) occur.

The originality of the expected results - A large number of recently published papers were looking at different modalities of RT with constant loads, different periodization models and their effects on muscle recovery in this specific population. However, their findings clearly showed that regardless of RT training or different training periodization strategies type II muscle fibers kept declining with muscle disuse and aging. Thus, one could speculate that sudden mechanical overload approach (or variable iso-inertial load) will be a viable tool to tackle muscle power and function loss via additional type II muscle fibers recruitment patterns. In addition, the present study aims to determine whether some specific blood markers (like agrin) could detect neuromuscular junction alterations following these experimental protocols.