What Are The Upper And Midsole Of A Shoe?

The upper and midsole are two core components of the shoe, and their functions are different: the upper is the outer structure that wraps and anchors the foot, while the midsole is the cushioning and supporting layer between the upper and the outer sole. Its specific definitions, functions and characteristics are as follows:
I. Upper layer: ``external barriers' 'for packaging and safety
The upper is the part of the shoe that comes into direct contact with the foot and ankle. Its main function is to wrap the foot, lock the shape of the foot, and protect the foot from external friction and impact.
Core Functions
* Packaging and security measures: The upper has a front box, collar and lacing/Velcro to stabilize the feet and prevent slipping during exercise (e.g. running shoes with dynamic flylines for added support).
Foot protection: Isolates external debris (such as dust and small rocks) and cushions the impact between the foot and external surfaces (such as thick leather on top of work shoe to prevent scratches).
Comfortable breathability: Through materials or structural design (such as mesh fabric and ventilation holes), it helps your feet lose heat and sweat and improves comfort (such as turtlenecks, commonly used in sneakers).
Commonly used materials:
Textiles: Lightweight breathable Flyknit fabric (suitable for trainers), canvas (durable, versatile, suitable for canvas shoes), mesh fabric (high breathability, suitable for summer shoes).
Leather: Genuine leather (soft texture, suitable for dress shoes and work shoes), synthetic leather (cost-effective, easy to clean, suitable for casual shoes), microfiber leather (durable and soft, often used to support the shoe uppers of sneakers).
Other:
TPU (transparent or coloured plastic material used for upper decoration or partial support, such as head protectors on roller skates), neoprene rubber (for upper elasticity in water shoes and loafers).
Key Structures:
Toes: Protect your toes; common types include round toes (comfortable without constricting), pointy toes (to make your feet look longer) and square toes (retro and for casual footwears). Vamp: The area covering the ankle is divided into high-top (ankle protection, such as combat boots and basketball shoes), medium (balance, protect and bend, such as hiking shoes) and low (help and bend, such as roller skates and canvas shoes).
Closure methods: Tie (adjustable size, wide range), Velcro (easy to open and remove, suitable for children's shoes and loafers), slider (not closed, commonly used in light shoes).
ii. Middle-sole: a "core shock absorber" that cushions and supports. The middle of the sole, located in the upper and lower parts of the shoe, acts as the "shock absorber core" of the shoe, absorbing the effects of walking or movement while providing foot support to prevent fatigue or injury.
Core features: cushioning and shock absorption: absorbs the impact of foot impacts through the elastic deformation of the material (e.g. impact of foot landing while running; the midsole relieves pressure on knees and ankles). Support and stability: prevent excessive foot deformation through material stiffness or structural design (for example, arch support reduces foot fatigue in flat feet and torsion plates prevent foot deformation during exercise).
Height Adjustment: The thickness of the middle sole determines the overall height of the shoe. Thicker midsoles (such as high-soled and flat shoes) make the wearer look taller, while thinner midsoles (such as dress shoes and canvas shoes) are closer to the ground, improving walking stability.
Commonly used materials:
EVA: Lightweight, flexible and cost-effective, EVA is the most commonly used midsole material (such as most loafers and entry-level sneakers), but is prone to compression deformation over time, reducing shock absorption effect.
Foamed Rubber: Elastic, wearable and pressure-resistant, it absorbs shocks better than EVA (e.g., Adidas Boost, Nike ZoomX, uses special foam process to improve rebound performance, suitable for professional sneakers).
Polyurethane: Harder than EVA, better support, less yellowing (suitable for midsole, balance support and comfortable clothing and work shoes), but slightly heavier.
Other: Carbon fiber plate (lightweight and rigid, used on the middle soles of professional running and basketball shoes for high torsion stiffness and propulsion), latex paint (soft and smooth for casual and sneaker feet).
Key Structures:
Arch support: Add a rigid material (such as a TPU support plate or carbon fiber plate) to a mid-arch or design a raised structure to relieve pressure on flat or high-arched human feet.
Torsion Plate: Embedding long strips of rigid material (mostly TPU or carbon fiber) in the midsole to prevent excessive torsion during exercise (such as the midsole of basketball and running shoes to reduce the risk of ankle sprains).
Zoned Design: Use materials of different densities according to foot pressure (e.g. soft material for front foot bounce and hard material for back foot support common in professional running shoes). Bottom line: Simply put, the upper is responsible for "wrapping and protecting the foot," which determines the shoe's appearance, comfort and support; the middle sole is responsible for "cushioning and supporting the foot," which determines the shoe's shock absorption, support and feel. The experience of shoes (e.g., whether they are tight or shock absorption) depends largely on the material / structure of the upper and sole.