Why do some people respond so well to training while others struggle?

Why do some people struggle to respond to Exercise – Benefits May Vary from Person to Person

Why do some people not respond to exercise? Naas Physio Clinic -

Research at the Joslin Diabetes Centre has identified a molecular switch that may provide an explanation for how some people respond really well to exercise, whether cardiovascular or resistance based, while others performing the same activity do not. The name of the protein “switch” is c-Jun N-terminal kinase (JNK).

When the protein is activated it stimulates muscle growth in response to exercise; however, when inactive, muscles respond by improving their endurance & aerobic capacity. It is the first time that this protein has been researched in this capacity.

The relevance of this is that if a group of people do the same  exercise programme then some will have huge improvements in aerobic capacity while others will have minimal or no response.

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Why don’t I respond to exercise? Research Suggest a Protein Switch May Play a Role

When the researchers compared a group of mice that had the JNK protein switched off with a normal group of mice they found that the altered mice had a significantly higher increase in aerobic capacity and greater development of muscle fiber types that improve endurance capacity.

Aerobic capacity acts as a predictor of diabetes & cardiovascular disease and therefore the ability to respond to cardiovascular exercise is a key determinant of health. Diabetes and cardiovascular disease are the two most common chronic illnesses affecting Western society. Cardiovascular disease is the most common cause of death in Ireland with 1 in 3 dying from the disease.

The researchers found that the JNK protein was highly activated in the muscles of people who performed leg weights but not in those performing endurance exercises. However, a significant minority of individuals did demonstrate some JNK activation in their leg muscles during endurance exercise. This may inhibit improvements in endurance capacity in those individuals.

The researchers are now investigating ways of inhibiting JNK activation such as developing approaches that reduce the mechanical stress on muscles.

Further evidence suggests that “improvements in aerobic capacity are blunted and aerobic remodelling of skeletal muscle is impaired in several animal models associated with chronic hyperglycaemia”.

The authors suggest that current changes in diet and lifestyle, such as consumption of high carbohydrate and processed foods, can give rise to altered blood sugar control and, therefore, impair the capacity of the muscle to respond to training. 

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Tara L. MacDonald, Pattarawan Pattamaprapanont, Prerana Pathak, Natalie Fernandez, Ellen C. Freitas, Samar Hafida, Joanna Mitri, Steven L. Britton, Lauren G. Koch, Sarah J. Lessard. Hyperglycaemia is associated with impaired muscle signalling and aerobic adaptation to exercise. Nature Metabolism, 2020; DOI: 10.1038/s42255-020-0240-7. https://pubmed.ncbi.nlm.nih.gov/32694831/


Picking the Right Running Shoes

How Do I Pick the Best Running Shoes for Me?

Before deciding how to pick the best running shoes, it is important to dispel a few myths regarding running shoes and what their role is.

Research suggests that running related injuries have not decreased over the past 40 years despite the constant ‘advancement’ in research and shoe development.

There is a widespread belief that foot pronation and differences in leg length are major causes of knee, ankle & back pain. It is rare that a day goes by without a patient mentioning one of these factors as the potential cause for their current injury.

Conventional wisdom suggests that over-pronation is one of the major drivers of injury, especially in runners. When the published literature is analysed, any such link between foot posture & leg length varation with injury is shown to be less clear cut.

For example, a recent prospective study found leg length discrepancy was not associated with running injury in recreational runners (Hespanhol Junior et al. 2016).

The most common issue that I hear patients bring up in the clinic is that they have been told that they have a flat foot (pronation) and therefore they have been provided with orthotics to ‘correct’ this. Let’s firstly address the issue of foot pronation and injury risk.

Shoe inserts and orthotics have been used for decades to prevent injuries in runner’s. Even though there was no research to substantiate the claim, foot pronation was considered one of the major variables in injury rates in the early scientific literature. It therefore was considered to be one of the major considerations in shoe design as a means of decreasing injury rates.  

The main risk factor for having a running-related injury is having had a previous injury in the last 12 months.

picking the right running shoes


Foot pronation is not associated with increased injury risk in novice runners wearing a neutral shoe: a 1-year prospective cohort study

The commonly held belief that excessive foot pronation is associated with an increased risk of injury is not backed up by the scientific literature. Therefore, this brings into question the benefit of anti-pronation shoes and the use of orthotics to prevent injury in runners.

Results of this study showed that at one year follow-up compared, when compared with a neutral foot posture, no significant differences were found after 250 km of running for highly supinated feet, supinated feet, pronated feet, and highly pronated feet.

Most interestingly, the findings revealed that pronators had a significantly lower number of injuries/1000 km of running than those with a neutral foot posture. However, those with highly pronated feet had the highest number of injuries per 1000km of running.

Conclusions: The results of the present study contradict the widespread belief that moderate foot pronation is associated with an increased risk of injury among novice runners taking up running in a neutral running shoe. More work is needed to ascertain if highly pronated feet face a higher risk of injury than neutral feet.

Ref: Nielsen et al. (2014). Foot pronation is not associated with increased injury risk in novice runners wearing a neutral shoe: a 1-year prospective cohort study.  British Journal of Sports Medicine.

Ref: http://bjsm.bmj.com/content/early/2013/06/12


Ning et al. (2015). Running shoes and running injuries: mythbusting and a proposal for two new paradigms: ‘preferred movement path’ and ‘comfort filter’. British Journal of Sports Medicine; 49: 1290-1294.

The authors of this study report that changes in the actual plane of motion of the foot were small & not systematic. Changes occurred primarily in the range of movement but not in the path of movement.

They report that shoe conditions that are more comfortable are associated with a lower movement-related injury frequency than shoe conditions that are less comfortable. 

The authors propose that an athlete should select a running shoe using their own comfort filter. This automatically reduces the injury risk.

In other words: if it feels good to you then you may have a decreased injury rate by wearing it

Are orthotics good for Shin splints?

The theory is that decreasing foot pronation should reduce the traction of the muscles where they insert into the shin bone. However, the evidence for orthotics in reducing shin splints is inconclusive at present.

Interestingly, Newman et al. (2013) reported that prior orthotic use is a highly significant risk factor for the development of shin splints.

The authors reported that orthotic use is a risk factor for shin splints and therefore they are NOT USEFUL for preventing shin splints.

Does running style impact on shin pain?

Loudon & Reiman (2012) assessed the running technique in individuals with shin splints and compared this to individuals without a history of the condition.

Three-dimensional analysis in runners measured peak hip internal rotation, pelvic tilt, and knee flexion.

The authors reported that the runners that had a history of shin pain demonstrated significantly greater pelvic tilt, hip internal rotation and less knee flexion than the pain-free group. The authors suggest that increased pelvic tilt can create valgus moment due to the body’s center of mass shifting medially.

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What Your Exercise Habits Might Say About How Long You’ll Live

What Your Exercise Habits Might Say About How Long You’ll Live

A new study shows the importance of consistent exercise into later life in determining lifespan. Previous research has shown that exercise is protective against disease; however, if people stop exercising in their later years then such benefits rapidly disappear.

On a more positive note, a new study suggests that people that commence exercise in midlife, even if they have not exercised for years prior to this point, can rapidly gain most of the longevity benefits associated with regular exercise.

The parts of the globe where people live the longest are often referred to as the ‘blue-zones’. When looking at the so-called ‘blue zones’ across the globe, one common characteristic of these groups, aside from social integration, is a consistent level of exercise that is sustained into old age.

Most research into exercise only monitors participants at one stage of their lives. In this research published in the Journal of the American Medical Association, data from 315,059 participants was analysed to determine exercise habits across their lifespan.

Analysis of the data demonstrated that participants who had been sedentary throughout their lives were most likely to have died, particularly from heart disease. Those who were consistently active, were 30 to 35 percent less likely to have passed away and 40 percent less likely to have died of a heart attack.

Exercise into old age. Naas Physio Clinic

Exercising Into Old Age is the Key

The most relevant finding from this study was that those that had stopped exercising but commenced again in their 40s or 50s had similar protection against premature death as those who had exercised consistently throughout their lives.

A note of caution also applies to those who think that being fit in their youth can be protective in later years. The study showed that those that were active and subsequently ceased exercise in middle age were as likely as the always-inactive group to have died.

The Common Mistake that Stops People Exercising Consistently

In my experience people often set lofty goals when commencing exercise. For example, they may start running 1k and have the ultimate goal of running 10k or doing a marathon. Some people complete this goal and then stop exercising altogether, or in setting the bar too high, they place too much pressure on themselves and stop exercising altogether. This research demonstrates that consistency is the key when it comes to exercise. For this reason, it is better to keep your exercise enjoyable, rather than turning it into a chore, which can sometimes occur when goals are set that are beyond your capacity to sustain in the longer-term.

The take home message is this: if you are active now, it is critical that it is sustained. Indeed, the older you are, the higher your risk of chronic disease, and therefore, the greater the potential benefit derived from regular exercise.

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