Written by Ben Bunting: BA(Hons), PGCert. Sport & Exercise Nutrition. L2 Strength & Conditioning Coach.
In this article we look in to the benefits of concurrent training practices to help improve muscle strength and stamina for the elderly population who are at an increased risk of falling and injury.
We shall cover the following areas:
- Exercise adaptation
Is Concurrent Training an Effective Strategy for Muscle Health?
It is understood that as a person ages, the mechanistic Target of Rapamycin (mTOR) signalling is diminished which results in muscle atrophy (sarcopenia) (Prashanth et al., 2012). Bone loss is adjacent to atrophy due to various age-related factors (Drinkwater, 1995).
It is considered that a combination of aerobic (cycling) with resistance training such as squats for two gyms sessions per week is suitable for the elderly. Yet the acute and chronic benefits of RT may be lost when combined with endurance exercise within a concurrent exercise programme.
It is the aim to understand whether concurrent training (CT) is an effective method of improving protein balance and establish the optimum volume and intensity to be applied.
It is widely considered that resistance and endurance training are both regarded to help maintain a higher quality of life (Sillanpaa et al., 2012). We outline each exercise type below.
Endurance exercise is typically of low load bearing and over a long duration of time such as running, cycling and swimming.
Consistent training such as combining high intensity interval training with long, slow or moderate pace running leads to an improved capacity of endurance performance by increasing mitochondrial biogenesis (cells increasing mitochondrial mass).
This is due to increases in Adenosine monophosphate (AMP), calcium ions (Ca 2+) and nicotinamide adenine dinucleotide (NAD +), (NAD+ declines with age). In turn this stimulates the activation of sensing proteins and transcriptional Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1a).
Biogenesis alongside capillary density improves oxygen transport, energy production (greater glucose uptake) and delay onset muscle soreness (Joyner and Coyle, 2008).
Mitochondrial mass is the net result of the net increased balance between biogenesis and degradation that is linked to ageing. This correlates with other age-related diseases and decline of organ function.
Degradation leads to a decline of Adenosine triphosphate (ATP) which will impact cell function and reduce muscle contraction among additional functions.
Endurance activity results in fatigue resistance and improved aerobic metabolism.
Typically, strength or resistance training consists of higher loads within short periods of time that would engage type 2 muscle fibres and change neural adaptations. A good example is the bench press.
Muscle hypertrophy requires increases in protein synthesis via ribosome biogenesis from mechanistic target of rapamycin complex 1 (mTORC1) (Brooks et al., 2019). mTORC1 signalling is required for hypertrophy as a response to exercise, tissue repair and acts as a central node.
The required mechanisms are mechanical loading, branch-chains amino acids and growth factor.
Resistance training triggers this extracellular stimuli reaching the cell membrane to react with receptors, in turn activating intracellular signalling pathways. This changes gene transcription and protein synthesis to stimulate muscle remodelling.
Signalling pathways that mediate muscular development through activation of intracellular protein kinase B (PKB), myostatin and microRNAs play an important role for muscle function and adaption.
This adaption will include increased myofibrillar resulting in improved strength, power, and muscle size.
It has been identified that bouts of low load exercise performed to failure can lead to strength, whereas short burst levels of high intensity can result in endurance adaptions (Rasmus et al., 2018).
A trial demonstrated that V02max improves during CT as well as strength and muscle cross sectional-area (de Souza et al., 2013).
This example shows that the p70S6K1 total protein increased due to phosphorylation dependent on Mtor signalling. The kinase activity increases protein synthesis and rapid cell growth.
Concurrent training has also led to increased mRNA levels when compared to just endurance activity. This results in improved mTOR signalling, positive impact on mitochondrial biogenesis and the activation of proteins signalling protein synthesis.
It is considered that CT increases muscular mitochondrial oxidative capacity, and thus improves muscle health, regardless of age (Irving et al., 2015).
However, for serious performance increases, concurrent training results in compromised adaptions as the two genetic and molecular mechanisms are distinct and is not as effective as single mode training (Hawley, 2009).
Both resistance and endurance training will elevate muscle protein synthesis (MPS) (Knuiman et al., 2018) (Damas et al., 2015), it also triggers protein breakdown at a level that exceeds synthesis by altering anabolic and catabolic hormones.
Training in a fasted state creates a negative protein balance which will lead to protein degradation (Kumar et al., 2009).
Research dictates that a positive nitrogen balance is required to benefit from training, this can be achieved by consuming protein and carbohydrates that provide amino acids and insulin to stimulate MPS (Mori, 2014).
Aerobic performance and muscle declines with age (Buskirk and Hodgson, 1987) and resistance training is also beneficial to bone health for elderly people (Baechle and Earle, 2000)
Based on current literature, it is recommended that the elderly employ a training regime of concurrent activity, contrary to recommendations for the trained athlete.
The subject’s requirements are not to increase sporting performance; and therefore, is not susceptible to any potential performance loss that could be a result of mediating two opposing training adaptions.
Much of the literature regarding CT focuses on end state measures such as maximal VO2 capacity and maximal strength. From a performance perspective, the molecular responses are not linear. Therefore, maximum hypertrophy or mitochondrial biogenesis cannot be achieved compared to singular training.
Yet CT exercise programs have proven to be the most effective way to improve overall health status for elderly people.
Research demonstrates numerous benefits are attainable from CT including strength, gait, balance, reduced risk of falls, neuromuscular, cardiovascular activity, and other functional parameters for physically frail, elderly subjects (Cadore et al., 2013).
Intensity and Volume
Greater strength was achieved from progressive programs (20% progressing to 80% 1 repetition max) performed thrice weekly.
Effective endurance programs that include walking consist of 5-10 minutes duration which progressing to 60 minutes with an intensity of 70-75% of heart rate (HR). Cycling up to 80% of peak HR for a duration of 4 months has enhanced MPS (Short et al., 2004).
Sources confirm that CT programs spanning from 12 weeks up to 12 months result in significantly reduced (22-40%) incidences of falls. (Lord et al., 2003) (Barnett et al, 2003) (Clemson et al., 2012).
Furthermore, untrained people have a greater capacity to respond to exercise and activate molecular pathways which benefit more from CT rather than singular exercises (Coffey and Hawley, 2017).
Evidence has shown that to prevent any loss of potential hypertrophy (due to a calorie deficit which would impact MPS) during CT the frequency should be no more than 4 times per week and 70% of VO2max for best results (Hughs et al., 2018).
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