TRAIL RUNNING,SPORT,RUNNING,HIKING,TRAIL,THE UNITED KINGDOM,IRELAND,MOUNTAIN,FELL RUNNING,ROAD RUNNING,TRACK RUNNING,GENERALLY,TAKES,HIKING TRAILS,MOUNTAINOUS,TERRAIN,DISTINGUISH,CROSS COUNTRY RUNNING,GENERAL,CROSS COUNTRY,IAAF,GOVERNED,DISCIPLINE,RACED,SHORTER,KILOMETERS,RUN OVER,LONGER,ROUTES,RUNNERS,INCREASING,THE UNITED STATES,ALONE,AMOUNT,ORGANIZED,RACES,THE PAST,THE WORLD NOW,THE HUNDREDS,NORTH AMERICA,CITE,LESS,IMPACT,STRESS,LANDSCAPE,URBAN ENVIRONMENT,PRIMARY,REASONS,MOVE,NATURE,INCREASE,COMPETITORS,TRADITIONAL,OFF ROAD,TRIATHLONS,ADVENTURE RACING,FIVE YEARS,NUMBER,PEOPLE,SOLO,BACKCOUNTRY,TRIPS,ULTRALIGHT,BACKPACKING,TYPE,COMMON,ORDINARY,DANGEROUS,FIND,CHALLENGES,REWARDING,ALSO KNOWN AS,HILL RUNNING,THE SPORT,RACING,UPLAND,COUNTRY,GRADIENT,COMPONENT,NAME,ORIGINS,THE ENGLISH,FELL,NORTHERN BRITAIN,THE LAKE DISTRICT,PREMISE,NAVIGATION,SKILLS,CARRY,ADEQUATE,SURVIVAL EQUIPMENT,THE ORGANIZER,SPECIAL,REPORT,PUBLISHED,OUTDOOR,INDUSTRY,FOUNDATION,AMERICANS,AGES,OLDER,RESEARCH,SHOWS,PARTICULARLY,HEAVY,THE MOUNTAIN,THE WESTERN,CALIFORNIA,THE NATURAL,SERENE,SETTING,VIEWED,SPIRITUAL,ACTIVITY,ROADSIDE,REASON,POPULARITY,ACKNOWLEDGMENT,RACE,KEEP,GREEN OR,ENVIRONMENTALLY FRIENDLY,DISTURBANCE,ENVIRONMENT,SHOES,AGGRESSIVELY,RIGID,COMPOUND,MIDSOLE,LIGHTWEIGHT,NYLON,PLASTIC,LAYER,PROTECT,FEET,PUNCTURE WOUNDS,SHARP,ROCKS,GRASS,DIRT,ROAD,CUSHIONING,THE SHOES,COUNTERPARTS,TARMAC,THE GROUND,THE BEST,STABILITY,UNEVEN,RECENTLY,SOLE,RUNNING SHOES,GAINING,ULTRA,MARATHONS,EVENTS,MILES,SHOE,EQUIPMENT,GARMENTS,WATER BOTTLES,SUNSCREEN,SUNGLASSES,GAITERS,INSECT REPELLANT,SPRAY,IVY BLOCK,ATTACH,CRAMPONS,THE BOTTOM,TRACTION,THE SNOW,ICE,ALTERNATIVE,WATER,BLADDER,DRINKING,TUBE,BACKPACK,WAISTPACK,CARRYING,THE TEN ESSENTIALS,REDUCE,THE HAZARDS,INHERENT,WILDERNESS,TRAVEL,LIGHT,HIKING POLES,COMPETITION,SPEED,ORGANISED,GLOBALLY,SHORT,HISTORY OF,BODIES,EXAMPLE,THE AMERICAN,ASSOCIATION,THE US,THE INTERNATIONAL,HIGH PROFILE,ULTRAMARATHON,DISTANCE,SIMILAR,TERMS,COMPARE,CONTRAST,TIMES,STANDARD,MARATHON,AID STATION,FOOD,BEVERAGES,THE COURSE,STAGE,TIMED,ENTIRE,DURATION,RUN,STOPS,STATIONS,STAGE RACES,EXIST,COMPLETE,SUPPORT,RUNNER,AMENITIES,STAGES,APART,MEDICAL,SLEEPING BAG,CHANGE,CLOTHES,EMERGENCY,FLARE,COMPASS,FLASHLIGHT,THE MARATHON,FEWER,AS NUMBER,LIMITED,TRAILS,NATIONAL PARKS,LIMITS,SAFETY AND ENVIRONMENTAL,POPULAR,THE ULTRA,DU MONT,EUROPE,ENDURANCE,RUN IN,FORCED,LIMIT,DEMAND,FISH RIVER CANYON,ULTRA MARATHON,KALAHARI AUGRABIES EXTREME,MOUNT CAMEROON RACE OF HOPE,PENINSULA ULTRA FUN RUN,RHODES TRAIL RUN,MOUNT FUJI,UTMF,TRANS JAPAN ALPS RACE,TRANSVULCANIA,BADWATER ULTRAMARATHON,BEAR,MILE,HARDROCK HUNDRED MILE,LEADVILLE,WESTERN STATES ENDURANCE RUN,KEPLER CHALLENGE,GRUNT,NEW ZEALAND,KOKODA,CHALLENGE,HILLWALKING,SKYRUNNING,