On Cloud X 3 review: The biomechanics of a true hybrid training shoe

Finding a single shoe that handles the heavy loads of weightlifting and the high impact of running is a biomechanical challenge. Here is an evidence-based breakdown of how the Cloud X 3 performs across different physiological demands.

“The central conflict in athletic footwear is stability versus energy return. To lift heavy safely, you need a rigid, non-compressible base to transfer force. To run without injury, you need compliance to absorb shock. The Cloud X 3 attempts to bridge this gap by using a firmer foam density that allows for proprioceptive feedback during lifts while offering just enough dampening for short-distance runs.”

Bruno Rodriguez, DPT, CSCS

The relationship

In the world of sports medicine and exercise physiology, “concurrent training” refers to the combination of resistance training and cardiovascular endurance work within the same program or session. While this approach is highly effective for general fitness and metabolic health, it presents a unique challenge for the musculoskeletal system—and specifically for the feet. The biomechanical requirements of lifting weights are diametrically opposed to those of running.

When an athlete performs a squat or a deadlift, the primary need is a stable surface area that minimizes center-of-pressure excursions (swaying) to prevent torque on the knees and lower back.^[1] Conversely, during the stance phase of running, the foot must absorb vertical ground reaction forces that can exceed 2.5 times body weight.^[2] Traditionally, this required two different pairs of shoes: a flat, hard sole for lifting and a soft, high-drop foam sole for running. The On Cloud X 3 enters the market as a “quiver killer,” designed to mediate these opposing forces.

Data suggests that using unstable, highly cushioned running shoes during heavy loading can increase instability at the ankle joint, potentially compromising force output and increasing injury risk. Alternatively, running in rigid lifting shoes lacks the necessary shock attenuation, increasing the transmission of impact shock to the tibial bone and knee joint. The relationship between the Cloud X 3 and the athlete is one of compromise: it provides a stable enough platform for moderate lifting (squats, box jumps) while retaining the mechanical characteristics needed for short-distance displacement (running 1–4 miles).

How it works

The biomechanical function of the Cloud X 3 relies on three specific engineering elements: the CloudTec sole, the Speedboard, and the upper construction. Understanding these helps explain why the shoe functions differently than a standard maximalist runner.

CloudTec and impact forces

The proprietary “CloudTec” cushioning system consists of hollow open tubes of rubber and foam on the outsole. Upon impact, these elements compress specifically to absorb vertical shock and then lock firm to provide a solid base for the push-off phase. In clinical terms, this variable density attempts to alter the rate of loading—how quickly force is applied to the foot.

For the runner, this reduces peak impact transient forces, which are often implicated in stress fractures.^[3] However, because the Cloud X 3 is designed for versatility, the foam is denser than in distance-specific models. This density prevents the “marshmallow effect” during lifting, where soft foam collapses under a barbell, leading to valgus collapse (inward buckling) of the knee.

The Speedboard and energy return

Embedded within the midsole is a semi-rigid plate known as the Speedboard. In biomechanical studies, midsole longitudinal bending stiffness (how hard the shoe is to bend) has been shown to improve running economy by acting as a lever arm for the plantar flexor muscles (calves).^[4]

In the context of the Cloud X 3, the Speedboard serves a dual purpose. During dynamic movements like box jumps or burpees, it loads with potential energy and releases it, aiding in explosive power. During static lifts, it provides torsional rigidity, preventing the foot from twisting mid-lift. This is critical for preventing plantar fascia strain during lateral movements.

Proprioception and stack height

Proprioception is the body’s ability to sense its position in space. High-stack shoes (thick soles) can blunt the sensory feedback from the mechanoreceptors on the sole of the foot. The Cloud X 3 maintains a relatively low profile compared to maximalist runners. Enhanced plantar sensation has been linked to better balance control and reduced risk of ankle inversion injuries.^[5]

For athletes performing functional fitness, this ground feel is essential. When you can feel the floor, you can better engage the intrinsic foot muscles to stabilize the arch. However, users should note the minimal arch support inherent in the design, which places greater demand on the posterior tibialis tendon to maintain arch height.

Conditions linked to it

Choosing the correct footwear is a preventive measure against several lower-extremity pathologies. The Cloud X 3 is positioned to mitigate specific risks associated with cross-training, though its design introduces limitations for certain populations.

Tibial Stress Syndrome (Shin Splints): This condition involves inflammation of the muscles, tendons, and bone tissue around the tibia. It is often caused by repetitive loading without adequate shock absorption. While the Cloud X 3 provides adequate cushioning for short runs (1–4 miles), systematic reviews suggest that runners with higher body mass or those running longer distances may require greater dampening to prevent tibial stress.

Plantar Fasciitis: This is the inflammation of the thick band of tissue that runs across the bottom of your foot. The Cloud X 3 has been noted for its lack of aggressive arch support. For athletes with flexible flat feet (pes planus), the lack of structural support during heavy loading or high-repetition bounding can exacerbate plantar fascia strain. Conversely, for those with strong intrinsic foot muscles, the neutral bed allows natural foot function without artificial propping.

Patellofemoral Pain Syndrome (Runner’s Knee): Instability at the foot often translates up the kinetic chain to the knee. By providing a wider, more stable base than a traditional narrow running shoe, the Cloud X 3 may help reduce internal tibial rotation, a key contributor to anterior knee pain during squats and lunges.^[6]

Symptoms and signals

Determining if a hybrid shoe like the Cloud X 3 is working for your specific biomechanics requires monitoring for subtle physiological signals. Pain is a lagging indicator; pay attention to these early warning signs during or after training.

Medial shin pain: Tenderness along the inner shin bone after a run suggests the cushioning may not be sufficient for your running volume or biomechanics.
Heel slippage: If the heel slides up and down during lunges or sled pushes, the heel counter may not be locking the calcaneus (heel bone) effectively, reducing power transfer.
Lateral foot cramping: Cramping on the outside of the foot often indicates the shoe is too narrow, compressing the metatarsals.
Knee wobble (Valgus): If your knees cave inward during squats, the shoe’s foam may be too soft for the weight you are lifting, or the lateral support is insufficient.
Hot spots: Localized redness or blistering on the toes or ball of the foot indicates friction, possibly due to the upper mesh not containing the foot securely during lateral cuts.

What to do about it

If you are considering the Cloud X 3 as your primary training shoe, follow this evidence-based protocol to ensure it matches your physiological needs and training intensity.

Perform the “Wet Test” or Single-Leg Stance Test

Before transitioning to a neutral shoe with minimal arch support, assess your foot type. Wet your foot and step on a piece of cardboard. If you see the entire imprint of your sole, you likely have low arches. Alternatively, stand on one leg barefoot. If your ankle immediately rolls inward, you may need an aftermarket insole to use the Cloud X 3 safely, as it lacks built-in corrective support.
Implement a graded transition protocol

Do not immediately run your maximum distance in these shoes if you are coming from a maximalist (highly cushioned) shoe. The lower drop and firmer ride increase the load on the Achilles tendon and calf musculature.^[7] Start with walking and gym sessions, then introduce running in 0.5-mile increments to allow tendon stiffness to adapt.
Limit usage by activity type

Restrict the Cloud X 3 to its intended “sweet spot”: mixed-modal workouts (HIIT), lifting sessions involving moderate weights (up to 1.5x bodyweight squats/deadlifts), and runs under 4 miles. For marathon training or powerlifting (1-3 rep max effort), switch to specialist footwear to minimize injury risk.

Myth vs Fact

Myth: “More cushioning is always better for your joints.”

Fact: Excessive cushioning can actually increase impact forces because the brain senses instability and tells the legs to strike the ground harder to find a stable platform.
Myth: “You can use running shoes for heavy deadlifts.”

Fact: Compressible running soles absorb the force you generate, reducing your lift capacity and creating instability that can lead to lower back injury.
Myth: “The Cloud X 3 prevents all impact injuries.”

Fact: No shoe prevents injury on its own. Load management (how much you train) and biomechanics (how you move) are the primary drivers of injury; shoes are merely tools to assist.

Bottom line

The On Cloud X 3 represents a successful biomechanical compromise for the hybrid athlete. It offers enough stability for safe movement in the gym and sufficient dampening for short, tempo-based running. However, its lack of aggressive arch support and firmer ride means it requires the wearer to have adequate intrinsic foot strength and ankle mobility. It is an excellent tool for CrossFit-style training or gym-goers who run to warm up, but it should not replace specialized equipment for long-distance endurance runners or competitive powerlifters.

References

Sato K, Fortenbaugh D, Hydock DS. Kinematic changes using weightlifting shoes on barbell back squat. Journal of strength and conditioning research. 2012;26:28-33. PMID: 22201687
Nilsson J, Thorstensson A. Ground reaction forces at different speeds of human walking and running. Acta physiologica Scandinavica. 1989;136:217-27. PMID: 2782094
Milner CE, Ferber R, Pollard CD, et al. Biomechanical factors associated with tibial stress fracture in female runners. Medicine and science in sports and exercise. 2006;38:323-8. PMID: 16531902
Stefanyshyn DJ, Nigg BM. Influence of midsole bending stiffness on joint energy and jump height performance. Medicine and science in sports and exercise. 2000;32:471-6. PMID: 10694134
Robbins S, Waked E, Gouw GJ, et al. Athletic footwear affects balance in men. British journal of sports medicine. 1994;28:117-22. PMID: 7921911
Barton CJ, Bonanno D, Levinger P, et al. Foot and ankle characteristics in patellofemoral pain syndrome: a case control and reliability study. The Journal of orthopaedic and sports physical therapy. 2010;40:286-96. PMID: 20436240
Kulmala JP, Kosonen J, Nurminen J, et al. Running in highly cushioned shoes increases leg stiffness and amplifies impact loading. Scientific reports. 2018;8:17496. PMID: 30504822