So you have no doubt heard that exercise can help you live longer and more importantly healthier? But for many, when exercise is mentioned it strikes fear into their soul as physical torture, running endless miles, having to attend a gym, “no pain, no gain” attitude to get the most out of its benefits.
It is important to remember that the use of s resistance training is nothing new to the world of health & medicine.
The intensity of muscle work ranges on a continuum from what your muscles do at complete rest (minimal tone), and then an increase in muscle work and energy as you are sitting there trying to stay upright and awake using your postural muscles and your lower leg gently contracting to maintain venous return. Up to the highest intensity of work they could perform doing what is known as a Maximal Isometric Contraction, where the resistive force is so high that the muscles can no longer create any limb movement (e.g. pushing against an immovable object like a wall and asking muscle to work maximally)
It is important to recognise that muscle performance can be measured by two factors, muscle strength (force) and muscle power.
The underlying component being muscular strength is the amount of contractile force a given set of muscle fibres can generate, muscle power combines factors of strength (force) and the speed at which a muscle contracts – thus with muscle power this includes limb movement speed, control, coordination.
In resistance training we do focus mainly on just improving the muscle contractile force or strength. In a rounded exercise programme, where we involve aspects of movement balance and coordination, we can actually add some muscle power which takes place following learning to better coordinate movement. A good example is young children. Their muscles will not increase in strength as a result of training, but we can improve the power their limbs can generate by teaching them how to coordinate movements and muscle actions better – this may be similar with older people too and hence reminding of us of those important teaching and movement techniques is essential to maintain safety and also effect.
A key physiological rational why we choose to work people at less the 70% VO2max (<80%) maximal heart rate, is not just for safety reasons but it is a level at which allows more continuous activity to be metabolically sustained.
Once we start to take the muscle work above this 70% level of intensity, the energy for muscular contraction increasingly relies on anaerobic metabolism, and the time it takes for muscle fatigue to set in becomes shorter and shorter. When we are working above our maximal aerobic capacity, and head towards maximal muscle work muscle fatigue can set-in in a matter of seconds. So for example; lifting something heavy, say a wheel barrow, or a heavy box, or furniture, usually in less than 30 secs you start to feel your muscles shake and burn and then you have to take a break.
By completing short bouts of muscular work this type of activity might be achievable, acceptable and beneficial and safe to a lower functioning patient. There is a high level of local muscle intensity but if the activity involves a localised muscle group, the aerobic demand can be kept relatively low.
If we look at muscle work sustainability, it provides us with descriptions of the different types of muscle work to which we refer in the various components of muscular fitness training.
Aerobic endurance muscular work – that which muscle contractions can be sustained in excess of 5 minutes but more often 10 minutes and hopefully 30 to 60 minutes
Muscular endurance – typically lasting between 30 seconds and 2 mins (20 to 100 repetitions)
Muscular strength–muscle work that fatigues in under 30 seconds (1 to 15 repetitions of muscle work)
The guidelines for resistance training focus on the types of activities where muscle work is challenged in 12 or less repetitions; however, even aerobic exercise and muscular endurance exercise can contribute to improvements in strength, especially in the low functioning patient.
However, the fundamental driving factor that promotes muscular strength improvement is the total volume. Although overload of any type will provide a stimulus for improvement, the higher the volume, the greater the result.
Correspondingly, muscular strength and endurance activities do have some benefits to improving aerobic fitness; again this is most apparent in the lower functioning individual.
The important aspect from a safety perspective is that during resistance training, as you move-up the continuum towards a maximal voluntary contraction, you need to reduce the size of the muscle mass engaged to prevent large sustained increases in afterload, which should be a consideration for those with certain medical conditions..
Here we can see that at low, moderate and high intensity training, when the activities are isolated to specified muscle groups, the levels of rate pressure product (RPP) do not change much between the low intensity (40% 1RM to 80% 1RM).
These RPPs are equivalent to moderate intensity exercise where the heart rate would be no higher than 95 – 110 bpm and the systolic BP no higher than 160mmHg.
Dynamic resistance exercises performed at 40%, 60% and 80% of 1RM produced much lower haemodynamic responses than those obtained during a treadmill stress test.
Current guidelines recommend abstinence from exercise training for 6 weeks post-sternotomy. This practice is not based on any empirical evidence, thus imposing potentially unnecessary activity restrictions. Delayed participation in exercise training promotes muscle atrophy, reduces fitness and prolongs recovery.
In light of this though caution should be exercised in those having undergone sternotomy. Lower body exercises should be started as soon as the patient is able to stand. If there is no sign of sternal instability then upper body movement should be engaged. That being said, any movement involving the sternum should be thoroughly risk assessed taking into account other factors and co-morbidities.
FITT principle to exercise
F Min 2 x per week (non-consecutive days)
I Borg(6-20) RPE 14 at final rep
T minimum 1 set, 8-12 reps (sets x reps x weight=total volume-the more the better)
T individualise to each patient
Initial weight should be set at a level that allows the participant to achieve the repetition range at a RPE11-14. For those new to RT the main emphasis is to allow time for MSK adaptation and also to develop good technique, reducing the risk of increased muscle soreness and injury. Each repetition should include the following: a slow, controlled movement (≈2 seconds up and 2 seconds down), one full inspiration and expiration, and no breath holding (Valsalva maneuver).
If maximal tests are available, eg, a 1 RM, then 40% of 1 RM for the upper body and 50% to 60% of 1 RM for the hips and legs can be used as the starting weight for the first training session. If a prior test is not available, start with an estimated easy to light weight. When the individual can comfortably (RPE 11) lift the weight for up to 12 repetitions, resistance can be increased by 5-10% for the next training session, or to a weight that can be lifted no less than 8reps. If the participant cannot complete the minimum number of repetitions (8reps) using good technique, the weight should be reduced.
Support and education is essential so that participants should find the appropriate weight to use within the correct repetition range. Because the level of fatigue (intensity) is an important factor for attaining optimal benefits and the performance of resistance exercise at a high level of fatigue has not been associated with an increased risk of precipitating cardiovascular events in healthy adults, resistance training to volitional or near-volitional levels of fatigue could be considered.
Individuals with a lower fitness level may focus on machine-based RT as this is regarded as safer, whereas advanced individuals may perform more complex free weight exercises. When assessing the load for a patient, the Borg RPE scale provides the patient’s own subjective stress perceptions so is a very good measure of capacity.
SPOR principle to exercise
Specificity- Training must be specific to the activity you are doing, the type of fitness required and the particular muscle groups.
Progression- As your body adapts to a particular training level, you need to progress to a new level of fitness. To do this a gradual increase in intensity is needed to create an overload. Aim for 5-10% per week or be guided by RPE.
Overload- Training must be increased to a higher level than normal to create the extra demands to which your body will adapt.
Reversibility- The progressive effects of training can reverse. If exercise is reduced in intensity or stopped then the benefits will also.
RT is safe and effective in in those with chronic health conditions including CVD and myocardial dysfunction groups and may actually be a starting point for low functioning patients prior to doing more aerobic exercise.
So advise every patient pushing, pulling and carrying!