Trainer fungi. Coloured scanning electron micrograph (SEM) of fungal spores cultured from a used trainer. Footwear is a breeding ground for athlete's foot (tinea pedis), onychomycosis, fungus spores, and fungal infection. All may continue to thrive in the warm, dark, and moist environment of an infected and unsanitized pair of shoes. Fungus can live in your shoes for up to 20 months. Magnification: x2000, when printed 10 cm wide