No matter how fit or strong you are, we all have days in the gym when our workout feels weak.

When this happens, it is important to take it in your stride and adjust your expectations for your session. After all, we can’t all perform at 100% every day.

It is important to acknowledge that we can often feel flat for various reasons, including these 5 common causes for a lacklustre workout…

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1. You’re under-recovered

We often focus disproportionately on the potential impact that excessive training can have on our bodies, our injury risk and our ultimate performance, but under-recovery is typically a more common issue.

Fatigue can set in when we engage in prolonged periods of intense or high-volume exercise without adequate rest or suitable training periodisation. It can also occur if you suddenly increase your training volume, frequency and/or intensity, or follow a monotonous training programme.

Other factors can also contribute to feelings of fatigue, such as emotional, psychological, environmental or physiological stress, poor nutrition, calorie deficiencies, or excluding entire food groups like carbs or fats, from your diet.

While both states share many of these characteristics, overtraining is typically chronic in nature and takes longer to overcome.

Under-recovery is different in that it is often more transient and you can typically bounce back in a few days with some extra sleep, an extra rest day or two, or a reduction in training volume and intensity (commonly known as a training taper).

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2. You slept badly

While one bad night is unlikely to impact too heavily on your training, cumulative sleep debt – multiple consecutive nights of poor quality and short duration sleep – not only affects your cognitive function but also negatively impacts your physiology and performance.

Poor sleep impacts our hormones, which can mess with energy regulation and raises stress hormone levels (like cortisol).

These effects can break down muscle and decrease the production of important anabolic hormones, such as testosterone and growth hormone, which are important for strength and recovery.

A lack of adequate sleep can also reduce motivation levels and impede your ability to recover from exercise.

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3. You’ve eaten poorly

You need to fuel your body with the right foods. Without sufficient calories and energy from stored or ingested carbohydrates or fat, your high-intensity workout will likely fall flat in the first few reps.

You should ideally eat a meal consisting of complex carbohydrates and protein roughly 90 minutes before your workout.

Complex carbs deliver a steady and sustained release of energy to get you through your training session while the protein limits muscle loss and supports recovery.

You can also include a small portion of monounsaturated fat (found in foods like nuts, avocados and olive oil) before a workout, as these fats offer a dense energy source that also supports hormone production.

Consuming a meal that contains a large portion of high-glycaemic index (GI) from processed carbs or sugar can also wreak havoc with your blood sugar levels. The resultant swings in circulating glucose levels are associated with fatigue, decreased energy, and reduced alertness.

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4. Your motivation needs a makeover

Even the most committed and dedicated gym-goers struggle to find the motivation to consistently train at their best.

The problem with motivation is that it is dynamic and influenced by multiple factors, from our moods and emotional state to the weather and the type of day we’re having.

A stayed workout plan that lacks diversity is another sure-fire way to extinguish your passion for training, and falling into a workout rut will negatively impact your motivation levels.

It is important to keep challenging yourself with new exercises or routines to keep things interesting and exciting in the gym.

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5. You’re stressed out

Stress can distract your mind, overwhelm your body and drain your energy. Whether your thoughts are consumed by a work deadline, relationship drama or family pressures, you’ll feel fatigued when you hit the gym and lack strength during your workout.

And research confirms this link. A 2009 study1 published in the Journal of Applied Physiology showed that mental fatigue can have nearly as much impact on athletic performance as muscle exhaustion.

The theory, which lead researcher Samuele Marcora calls the psychobiological model of exercise tolerance, combines psychology with biology and physiology to quantify the impact of stress of physical performance.


  1. School of Sport and Exercise Sciences, University of Kent; Mental Fatigue Impairs Physical Performance in Humans; J Appl Physiol, 2009 Mar;106(3):857-64. doi: 10.1152/japplphysiol.91324.2008. Epub 2009 Jan 8.