title: Effect of rolling resistance on poling forces and metabolic demands of roller skiing.
abstract: OBJECTIVE
  To examine the effect of an increase in roller ski rolling resistance on the physiological and upper body demands of roller skiing with the V2-alternate technique.
  
  
  METHODS
  Nine highly skilled cross-country skiers roller skied at three paced speeds on a flat oval loop using roller skis with high (HiR) and low (LowR) rolling resistance. Oxygen uptake (VO2), heart rate, and poling forces were measured during the last 30 s and rating of perceived exertion (RPE) was requested immediately after each 4-min bout of roller skiing.
  
  
  RESULTS
  VO2 and all force-related variables increased significantly with speed and were higher (P < 0.01) for HiR at given speeds. Poling time was similar between HiR and LowR, whereas poling recovery time was shorter (P = 0.0002) and cycle rate was higher (P = 0.002) for HiR. For given VO2 levels, peak and average forces, heart rates, and RPE values were similar between HiR and LowR, whereas average poling force across the cycle was greater (P = 0.006) and duty cycle (i.e., percentage of cycle when poling forces were applied) was higher (P = 0.0001) with HiR.
  
  
  CONCLUSIONS
  1) The decrease in poling recovery time and increase in cycle rate associated with an increase in roller ski rolling resistance is comparable to the effect previously observed from increasing grade and probably occurs as a means of limiting deceleration. 2) Since changes in rolling resistance do not alter the relationships of RPE and heart rate with VO2, the central cardiovascular adaptations from roller ski training should not be affected by the rolling resistance of the roller skis. 3) Higher resistance roller skis are likely to induce greater upper body aerobic adaptations than lower resistance roller skis.
authors.affiliation: Department of Physical Medicine and Rehabilitation, The Medical College of Wisconsin and VA Medical Center, Milwaukee 53295, USA.
authors.forename: G Y
authors.initials: GY
authors.lastname: Millet
authors.forename: M D
authors.initials: MD
authors.lastname: Hoffman
authors.forename: R B
authors.initials: RB
authors.lastname: Candau
authors.forename: J B
authors.initials: JB
authors.lastname: Buckwalter
authors.forename: P S
authors.initials: PS
authors.lastname: Clifford
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D004734:Energy Metabolism; D006339:Heart Rate; D006801:Humans; D019344:Lactic Acid / Q000097:blood / Q000378:metabolism; D008297:Male; D010101:Oxygen Consumption; D010809:Physical Fitness / Q000502:physiology; D012865:Skiing / Q000502:physiology*
chemical_list: D019344:Lactic Acid