Muscle-Tendon Mechanics During Locomotor Tasks, Efficacy of Collagen Supplementation for Older Adults

Liverpool John Moores University21 enrolled

Overview

Older adults are at higher risks of tripping and falling than young adults. These falls may lead to serious injuries (bone fractures, head trauma…) and premature death. They also have an important economic cost for the society. One of the reasons identified for this increased risk of falling is the modification of muscles and tendons functional and architectural parameters with age. It is now well established that muscles of older adults are smaller and weaker, while tendons, that modulate the outcomes of muscle contraction, are less able to resist to tension and transmit forces more slowly than in young age. These changes have functional implications, especially in tasks that require to quickly generate high forces, such as recovering from a trip. This study aims to determine the links between muscle-tendon characteristics and locomotion, and to understand whether they can be improved by a four-months collagen supplementation. The investigators will measure the muscular strength and tendon stiffness of lower limb musculotendinous units (MTU) for older adults using isokinetic dynamometry (IKD) and ultrasounds. Participants' abilities to recover from a trip will then be evaluated using a custom built tripping device while walking on a treadmill (participants will wear a whole body harness attached to a rope secured to the ceiling). These performances will be linked to MTU characteristics and compared between both age groups. Finally, the investigators will evaluate the effect of a nutritional supplementation on the mechanical properties of elderly tendons and its potential impacts on their ability to safely recover from a trip, on their lean mass, and on other life quality related markers (joint pain, balance, stair climbing capacities...). The investigators expect that this study will lead to a new intervention aiming to improve the safety of older adults performing their daily activities using nutritional supplementation, which is known to have better adherence than training interventions.

Being able to walk safely, to go up and down stairs and to recover from an unexpected gait perturbation are vital for older adults' autonomy, home maintenance and life quality. It is therefore of major interest to understand the mechanisms responsible for older adults (OA) decreased functional abilities. This study aims first to understand the links between muscles and tendons characteristics and functional capacities of OA, and second to evaluate whether a 4-month collagen supplementation can improve OA musculotendinous properties, thereby improving their function. Trips are caused by an unexpected perturbation during the swing phase of gait (i.e. when the foot is not in contact with the ground). Recovering from a trip requires the production of fast and large muscle torques at the hips, knees and ankles joints to counteract the forward rotation of the body, and the propulsion of the forward leg anteriorly to the centre of mass. For OA, falling when walking on a flat surface is potentially damaging, and falling while using stairs is even more dangerous. Indeed, over 65% of falls leading to brain injury in OA happen in stairs and 10% of fall death in the US happen in stairs. Older adults with joints problem are more susceptible to report difficulties when using stairs than those without. Those with multiple joints problems are also up to 20 times more likely to have difficulties in stair climbing than OA without joint problems. Mechanically, older adults operate closer to their maximal joint moment capacities at the knee (ascent and descent) and ankle (ascent). They thus have less reserve to adjust to any perturbation that could happen and are at more risks of falling than young adults (YA). Normal gait, but also trip recovery and stair climbing are dependent on the muscles and tendons capacities to produce and transmit adequate forces in a short amount of time. With age, muscular and tendinous properties decline: muscles, that are responsible for the production of forces, become weaker and smaller, and tendons, that are responsible for the transmission of forces from muscles to the skeleton, become less stiff. It has been shown that changes in the gastrocnemius tendon's properties affect the ability of elderly to maintain balance during dynamic and demanding postural tasks, complicating OA daily living activities. This may especially be so when the individual is not only required to generate large joint moments, but to do so quickly, as is the case when trying to avoid a fall. OA with decreased muscle and tendon properties do not generate and transmit adequate forces in magnitude and velocity, which may be responsible for their decreased ability to recover from a trip and in some cases may lead to falls. Therefore, interventions that improve muscle-tendon properties of OA are likely to have benefits for recovering from a trip and preventing a fall occurring. Training interventions have been developed to minimise the effect of age on OA physical condition but although strength training can improve tendon stiffness and muscle strength, participants' adherence to these protocols can be low. Developing interventions with similar effects and which are easier to follow (that do not require modification of participants' routine) is thus of major interest. It has been shown that collagen supplementation improves the blood collagen synthesis and the resistance to tension of collagenous tissues in the body. In this study, the investigators will test a collagen supplement designed to improve joint, muscle and whole-body function. Although the investigators understand that the structure of muscles and tendons determines their function and has key roles in overall physical function and ability to recover from a trip, the investigators do not yet fully understand these mechanisms and how best to improve them. The research area will be centred upon the muscle-tendon properties and interactions that determine physical function in two different conditions (stair climbing and trip recovery), and whether these can be improved by collagen supplementation. The investigators will therefore evaluate changes in bone mineral density, lean mass, tendon stiffness, muscle strength, stair climbing and tripping recovery capacities before and after a 4-month supplementation period in 80 OA allocated either to the active product or to the placebo group.

Outcomes

Primary Outcomes

Tendon stiffness

Tendon stiffness will be measured as the change in tendon length per change in tendon force. Tendon lengthening will be measured using B-mode ultrasound as the displacement of the proximal insertion (myotendinous junction (MTJ) for the Achilles tendon and patellar insertion for the patellar tendon) during maximum voluntary contractions.