Motivation Depends on How the Brain Processes Fatigue

How do we decide whether or not an activity which requires work is ‘worth the effort’? Researchers at the University of Birmingham & University of Oxford have shown that the willingness to work is not static, and depends upon the fluctuating rhythms of fatigue.

Fatigue – the feeling of exhaustion from doing effortful tasks – is something we all experience daily. It makes us lose motivation and want to take a break. Although scientists understand the mechanisms the brain uses to decide whether a given task is worth the effort, the influence of fatigue on this process is not yet well understood.

The research team conducted a study to investigate the impact of fatigue on a person’s decision to exert effort. They found that people were less likely to work and exert effort – even for a reward – if they were fatigued. The results are published in Nature Communications.

Intriguingly, the researchers found that there were two different types of fatigue that were detected in distinct parts of the brain. In the first, fatigue is experienced as a short-term feeling, which can be overcome after a short rest. Over time, however, a second, longer term feeling builds up, stops people from wanting to work, and doesn’t go away with short rests.

“We found that people’s willingness to exert effort fluctuated moment by moment, but gradually declined as they repeated a task over time,” says Tanja Müller, first author of the study, based at the University of Oxford. “Such changes in the motivation to work seem to be related to fatigue – and sometimes make us decide not to persist.”

The team tested 36 young, healthy people on a computer-based task, where they were asked to exert physical effort to obtain differing amounts of monetary rewards. The participants completed more than 200 trials and in each, they were asked if they would prefer to ‘work’ – which involved squeezing a grip force device – and gain the higher rewards offered, or to rest and only earn a small reward.

The team built a mathematical model to predict how much fatigue a person would be feeling at any point in the experiment, and how much that fatigue was influencing their decisions of whether to work or rest.

While performing the task, the participants also underwent an MRI scan, which enabled the researchers to look for activity in the brain that matched the predictions of the model.

They found areas of the brain’s frontal cortex had activity that fluctuated in line with the predictions, while an area called the ventral striatum signalled how much fatigue was influencing people’s motivation to keep working.

“This work provides new ways of studying and understanding fatigue, its effects on the brain, and on why it can change some people’s motivation more than others” says Dr Matthew Apps, senior author of the study, based at the University of Birmingham’s Centre for Human Brain Health. “This helps begin to get to grips with something that affects many patients lives, as well as people while at work, school, and even elite athletes.

Source: University of Birmingham

In Pictures: Decorative Sushi

Four Findings from a Systematic Review about Beer and Exercise

Ross Pomeroy wrote . . . . . . . . .

After a grueling sports match or a brutal workout, there’s often nothing more refreshing than a nice cold beer… But what about the drink’s intoxicating effects? When the human body requires recovery after strenuous exercise, will downing a beer actually backfire?

Patrick B. Wilson, an associate professor in exercise science at Old Dominion University, and Jaison Wynne, a PhD student in the Department of Human Movement Sciences at Old Dominion explored this, and a variety of other questions in the first systematic review of beer’s effects on exercise performance, recovery, and adaptation. Here are four key takeaways:

1. Athletes are much more likely than non-athletes to drink beer. Numerous surveys suggest that athletes from the collegiate level to the elite level are more likely to drink beer than non-athletes. This seems counterintuitive, as one might think that people who need their bodies to operate at peak performance would drink less. Not so.

2. Beer isn’t great for hydration after exercise. Wynne and Wilson found two studies where the researchers asked subjects to strenuously exercise, then drink beer. The exercise prompted the participants to profusely sweat, leading to an average 2% reduction in body mass from water loss. Afterwards, the researchers gave subjects water, nonalcoholic beer, ~5% alcohol beer, or a sports drink to replace all the fluids they lost. Subjects given beer retained fewer fluids, urinated more, and had worsened fluid balance a couple hours after exercise. These differences disappeared after a few more hours, however.

3. Moderate drinking the night before a competition likely won’t impair performance. A study that had athletes consume between zero and six beers the night before a test of muscle strength and endurance found that drinking two beers or less did not impact performance. However, drinking four or more was detrimental.

4. Regular drinking doesn’t seem to hinder athletic gains over many weeks of exercise. In one study, subjects were prescribed ten weeks of high-intensity interval training along with drinking either vodka, water, or beer after their workouts. There was no difference in physical outcomes between any of the groups – they all got fitter to the same degree. In another study, participants took part in a vigorous aerobic exercise program while drinking six 750-mL bottles per week of either 0.9% or 5.0% beer. Both groups’ cardiorespiratory fitness increased by the same amount, although the low-alcohol beer group enjoyed other metabolic benefits that the high-alcohol group did not, such as lower blood pressure and lower blood lipid levels.

Overall, Wilson and Wynne found that moderate beer consumption after exercise was generally harmless.

“Chronic changes in body composition, as well as muscle performance, adaptation, and recovery, seem largely unaffected by moderate beer consumption,” they wrote.

Source: Real Clear Science

Sea Bass with Orange Chili Salsa

Ingredients

4 sea bass fillets
salt and ground black pepper
fresh coriander (cilantro), to garnish

Salsa

2 fresh green chilies
2 oranges or pink grapefruit
1 small onion

Method

  1. Make the salsa. Roast the chilies in a dry griddle pan until the skins are blistered, being careful not to let the flesh burn. Put them in a strong plastic bag and tie the top to keep the steam in. Set aside for 20 minutes.
  2. Slice the top and bottom off each orange or grapefruit and cut off all the peel and pith. Cut between the membranes and put each segment in a bowl.
  3. Remove the chilies from the bag and peel off the skins. Cut off the stalks, then slit the chilies and scrape out the seeds. Chop the flesh finely.
  4. Cut the onion in half and slice it thinly.
  5. Add the onion and chilies to the orange pieces and mix lightly. Season and chill.
  6. Season the fish.
  7. Line a steamer with greaseproof (waxed) paper, allowing extra to hang over the sides to enable the fish to be lifted out after cooking. Place the empty steamer over a pan of water and bring to the boil.
  8. Place the fish in a single layer in the steamer. Cover with a lid and steam for about 8 minutes or until just cooked.
  9. Garnish with fresh coriander and serve with the salsa.

Makes 4 servings.

Source: Mexican Red Hot Cookbook


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