The rest that wears you out: Why a day at the beach can be exhausting

Every day, a community garden and a seaside promenade are all that separate Carmen Gutiérrez from Sardinero Beach in the Spanish city of Santander. As director of the Cantabria School of Film and Television, she could practically jump onto the sand from the privileged location of its main campus in Santander. Even so, she tries not to do so when she has an afternoon of work at the computer ahead of her.

“Because the beach is tiring,” she says.

In fact, if she returns home after a few hours by the sea, “I don’t feel like unpacking my beach bag. I just want to lie down on the sofa,” she admits.

The feeling will be familiar to any holidaymaker. Although, in theory, few activities seem more relaxing than spending hours stretched out on a towel under the sun, soothed by the breeze and the sound of the waves, it is common to return from a day at the beach feeling drowsy and low on energy. But how is it possible to end up exhausted after enjoying what is supposed to be the ultimate summer retreat?

A body that never goes on vacation

“People think the body is resting, but it’s doing enormous metabolic work,” Javier Ceballos, a sports medicine specialist and former doctor for Racing Santander, tells EL PAÍS.

Ceballos has been retired for several years and is a well-known figure in Santander. He spends much of his time playing beach paddle, a traditional paddle game popular along this coastal region.

Ceballos attributes the sensation of beach fatigue to three physiological mechanisms. The first is thermoregulation. “When ambient temperature rises, the body’s priority is to keep our temperature stable at around 37ºC [98.6ºF],” he says. To achieve this, the body activates a complex physiological system that consumes energy even if we are motionless under a beach umbrella. “While we’re lying on the towel, the body is working to prevent overheating.”

When the hypothalamus, the brain’s thermostat, detects excess heat, it instructs superficial blood vessels to dilate and activates sweating. As sweat evaporates, it helps cool the body. But although these processes often go unnoticed, they come at a cost. “The body is constantly making adjustments: blood flow to the skin increases, the heart has to work harder, and all of that ends up producing a feeling of fatigue,” the expert explains.

That demand is compounded by fluid loss. “Even if you’re still and lying down, you continuously lose fluid because of the heat, the breeze and sweating. Even mild dehydration makes the heart work harder and that also contributes to tiredness,” says Ceballos.

According to the Mayo Clinic, exposure to high temperatures — especially when combined with high humidity — can lead to a range of heat-related disorders, from muscle cramps to heat exhaustion and, in severe cases, heat stroke, a potentially life-threatening medical emergency. Symptoms include fatigue, dizziness, weakness, headache, nausea and difficulty concentrating.

Young children and older adults are the most vulnerable groups, since their ability to regulate body temperature is less effective, Ceballos warns. “In older people, the sensation of thirst appears later, which is why it’s so important to drink before you feel thirsty.”

The third mechanism involves the body’s defense against solar radiation. Even when sunburn does not occur, ultraviolet rays can generate oxidative stress and damage skin cells, triggering an inflammatory response. “The sun acts as an aggressor and the immune system responds,” says the expert.

As part of this process, the body releases immune-signaling molecules known as cytokines, which are also associated with the fatigue experienced during some infections. “They send signals that promote tiredness and force the body to rest in order to repair the damage,” Ceballos adds.

The beach is also not as passive an environment as it appears. Fatigue may begin even before setting foot on the sand. During summer, people often sleep poorly because of the heat or changing schedules, and waking up early to secure a good spot on the beach hardly helps.

Then comes carrying umbrellas, coolers, and beach gear, a physically demanding task, especially for those who lead sedentary lifestyles. And after that there are walks, swimming, games with children, or activities such as paddle and frisbee. Even walking on sand requires considerably more effort than many people realize.

An Italian study estimated that walking on sand requires nearly twice as much energy as walking on a firm surface. Researchers attributed the difference to the fact that the body recovers movement energy less efficiently with each step on sand, forcing the muscles to work harder to move forward.

“You have to keep lifting your foot because it sinks, and that requires a lot more energy,” says Ceballos, adding that he becomes particularly aware of this when he is playing beach paddle.

Precisely because he understands this physiological toll so well, Ceballos limits his time at the beach. “I stay two hours, two and a half at most.” His routine consists of playing beach paddle for just over an hour, staying hydrated throughout, going for a swim, enjoying a little sun while always protected, and then heading home.

Recommendations

To reduce the strain, Ceballos’ recommendations are simple. The first is to hydrate before feeling thirsty. “A sip of water every hour is essential.” He also warns against some false remedies: “Alcohol and sugary juices dehydrate you more. I would drink water and perhaps a beverage with electrolytes — sodium and potassium — but without sugar or not excessively sugary.”

He also emphasizes another basic rule: avoid the hours when solar radiation is strongest. “The worst hours are between 12 p.m. and 4 p.m.” He adds other precautions: avoid heavy meals, “which divert more blood to the stomach,” use appropriate sun protection, and take regular breaks in the shade.

Everything suggests that beachgoing should be enjoyed in moderation. “It’s not psychological; the body is working constantly,” he summarizes.

In fact, many people report feeling even more exhausted the following day. Ceballos explains that cellular repair, rehydration, and the restoration of the body’s internal balance all take time. “It’s the bill the body charges you.”

Perhaps that is why Carmen Gutiérrez has adopted her personal rule. Even though Sardinero Beach is only a few steps away from her workplace, she avoids going there if another afternoon at the office lies ahead. Simply because, as she puts it, “it’s tiring, and it gets everything sandy.”

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