#4 on this list
Polysorb Cross Trainer
Spenco
The Spenco Polysorb Cross Trainer has long been a go-to choice for outdoor enthusiasts who want reliable, everyday impact protection without spending $60 or more. Unlike insoles that rely on stiff nylon or carbon plates, the Polysorb uses a full-length polyurethane base paired with a softer EVA heel cushion and forefoot pad. Reviewers frequently award it top value honors for its immediate, out-of-the-box comfort. Underfoot, this insole emphasizes pure shock absorption. The polyurethane layer absorbs the repetitive sting of trail gravel, packed dirt, and pavement, making it a reliable drop-in replacement for worn factory insoles in day-hiking boots or cross-trainers. The arch support is gentle and flexible rather than rigid, which makes it forgiving for a wide variety of arch shapes, including people who find stiff composite footbeds uncomfortable. The clear trade-off is biomechanical control. If you struggle with severe overpronation, plantar fasciitis, or need rigid rearfoot stabilization under a 40-pound backpack, the soft Polysorb cap will compress under load where a rigid composite insole would hold firm. It also runs slightly thick through the forefoot, which can tighten the toe box in snug shoes. **Highlights** * Dual-density polyurethane and EVA design delivers reliable shock absorption * Targeted heel and forefoot pads provide dependable impact dampening * Flexible, non-intrusive arch profile accommodates diverse foot shapes out of the box * 4-way stretch fabric top cover reduces blister-causing friction * Budget-friendly price point makes it an economical replacement for worn stock footbeds **Watch-outs** * Lacks the rigid torsional support needed for heavy backpacking loads * Slightly thick forefoot can cramp shallow toe boxes
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#5 on this list
Running
Enertor
The Enertor Running insole is engineered around serious impact reduction for high-mileage runners and fast-moving hikers. Its defining feature is the integration of D3O smart material technology—a shock-absorbing polymer that remains flexible under low pressure but locks together to dissipate forces during sharp impacts. Outlets like GearJunkie recommend it specifically for athletes dealing with shin splints, heel pain, or joint wear from hard surfaces. In real-world running and fastpacking, the Enertor provides a noticeably different feel than traditional EVA or polyurethane insoles. The heel strike feels remarkably muted, actively dulling harsh ground shock without the spongy instability common in overly soft gel inserts. The arch support is contoured but flexible, bending with your foot through the entire gait cycle rather than holding your foot in a static, locked-down position. However, because the construction relies heavily on specialized dense foam rather than a hard thermoplastic arch shell, it does not correct heavy overpronation. It also weighs slightly more than minimalist running insoles, and the rubbery compound underfoot can feel firmer on cold mornings until your body heat warms the material up. **Highlights** * Integrated D3O material dampens repetitive impact shock through the heel strike * Dynamic flexibility supports natural foot mechanics throughout the running gait * Helps reduce joint and tendon strain during high-impact trail descents * Durable foam construction resists premature packing down over long seasons * Low-profile forefoot fits cleanly into standard running shoe volumes **Watch-outs** * Provides limited correction for severe overpronation or flat arches * Material can feel notably firm in freezing weather until warmed by your foot
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Specs side by side
| Spec | Polysorb Cross Trainer | Running |
|---|---|---|
| Arch Profile | Moderate and flexible | Medium flexible contour |
| Base Material | Dual-density polyurethane and EVA | Shock-absorbing foam with D3O polymer |
| Volume Profile | Medium to high volume | — |
| Top Cover | 4-way stretch friction-reducing fabric | — |
| Price Point | Approximately $30 | — |
| Trim Style | Cut-to-fit forefoot sizing | — |
| Support Mechanism | — | Dynamic impact dispersion |
| Footwear Type | — | Running shoes and light hikers |
| Sizing Method | — | Trim-to-fit forefoot |
| Primary Focus | — | Joint and heel impact reduction |
What our reviewers liked and didn't
Polysorb Cross Trainer
- Reliable impact shock absorption from dual-density polyurethane and EVA
- Gentle, flexible arch contour requires zero break-in period
- Friction-reducing stretch fabric top cover helps prevent hot spots
- Significantly more affordable than rigid composite insoles
- Lacks rigid torsional support needed for heavy backpacking loads
- Forefoot stack height can crowd shoes with shallow toe boxes
- Provides minimal motion control for severe overpronation
Running
- D3O polymer dampens harsh heel and forefoot impacts efficiently
- Flexible contour permits unrestricted, natural foot articulation
- High-density compound resists compressive packing out over high mileage
- Low-profile forefoot preserves normal toe-box space in running shoes
- Lacks rigid arch support needed to correct severe overpronation
- Material feels stiff in sub-freezing temperatures until warmed by the foot
- Slightly heavier than minimalist EVA replacement insoles
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