Jerry Rice trained on sand. So did the Brazilian national football team. Beach sprints, dune climbs, barefoot drills on shifting ground. The principle is simple: sand absorbs energy, so your muscles must produce more of it. Sand is unstable, so your stabilisers must work harder. Sand is uneven, so your proprioceptive system is always on.

The biomechanics of sand locomotion have been quantified in detail. A 2012 meta-analysis in the European Journal of Applied Physiology found that running on sand requires approximately 1.6 times the energy expenditure of running at the same speed on a firm surface. The increase is attributable primarily to the foot's sinking into the surface on impact, a phenomenon called 'sand deformation work', which means that stored elastic energy in the Achilles tendon and plantar fascia is dissipated rather than returned. Every step on sand is, in mechanical terms, a step on a surface that refuses to give anything back.

This has important implications for lower limb conditioning. The calf musculature, gastrocnemius, soleus, and the deep posterior compartment muscles, must work concentrically against sand resistance on every push-off. The intrinsic foot muscles, atrophied in most adults by decades of supportive footwear, are recruited constantly to maintain basic stability. The ankle complex, often the first joint to be injured in conventional training, is challenged through its full range of motion on every step rather than in the narrow band demanded by flat surfaces.

Erg Chigaga is not a beach. It is one of the largest and most remote dune systems in Morocco, covering over 100 square kilometres of undulating sand that rises in places to over 300 metres. The dunes are not flat. They are ridges, bowls, slopes, and faces that change shape with the wind. No two training sessions on the same dune are biomechanically identical because the dune itself changes between visits.

Training here is unlike training on any beach. The scale creates genuine physical challenge. A dune climb at dawn is a full-body cardiovascular event. The loose sand of a steep face demands that each foot placement be deliberate, sink too far and you lose ground, push too hard and you compress the surface and gain purchase. Finding the correct pressure distribution is an unconscious neurological calculation that the body makes several hundred times per dune climb. By the end of a thirty-minute dune session, neural fatigue is as significant as muscular fatigue.

The glute activation benefits of sand training are particularly well documented. A study published in the Journal of Strength and Conditioning Research found that sand-based plyometric training increased gluteus maximus activation by 24 percent compared to equivalent drills on grass. The mechanism is postural: the unstable surface forces a forward lean, which loads the hip extensors rather than the quadriceps and transfers demand from the knee joint to the hip. This is a functionally important pattern, most sedentary adults are quad-dominant and glute-inhibited, a combination associated with anterior knee pain, lower back dysfunction, and reduced running economy.

The impact reduction benefits of sand training are particularly relevant for guests recovering from lower limb injuries or managing chronic joint conditions. Ground reaction forces during running on sand are approximately 40 percent lower than on tarmac, according to studies conducted at the Sport Performance Research Institute in New Zealand. This means that sand running can provide equivalent cardiovascular and metabolic stimulus to road running with substantially less joint loading, a meaningful tradeoff for any adult whose training history includes impact-related damage. The instability that creates the additional muscular demand simultaneously attenuates the compressive forces that cause wear at the knee and hip.

We do not use the sand as a gimmick. We use it as the primary training surface because the research supports it. Studies on sand-based training show increased caloric expenditure, improved ankle stability, greater glute activation, and reduced impact on joints compared to hard surfaces. A two-hour morning session at Erg Chigaga achieves training adaptations that would require substantially more time on conventional surfaces, with lower injury risk and higher recovery potential.

At Umnya, the dune sessions are designed around the thermal window. Dawn is the optimal time: the sand is firm from overnight cooling, the air temperature is manageable, and the light is extraordinary. By mid-morning, loose surface sand begins to heat rapidly. Sessions move indoors or to shaded environments. The desert enforces its own periodisation, which happens to align closely with evidence-based recommendations for morning exercise and heat management in endurance populations.

The barefoot dimension of sand training deserves a specific note. Most retreat guests arrive with feet that have been in shoes for the majority of their waking lives for the past several decades. The plantar fascia, a band of connective tissue that supports the arch of the foot, is often thickened and inelastic. The intrinsic foot muscles are weak. Walking barefoot on sand for forty-five minutes per day over eight days produces measurable changes in plantar pressure distribution, arch height, and foot muscle strength, changes that transfer to gait efficiency and injury resilience in footwear.

The dunes are beautiful. But that is not why we train on them. We train on them because they make the body work in ways it has forgotten how to. The instability, the resistance, the scale, the absence of handrails and flat floors and calibrated surfaces, these are not challenges to be overcome. They are the point.