External Mechanical Indices of Resistance Exercise and the O2 Cost

Abstract

PURPOSE: (1) To measure external mechanical indices of Work & Power during bouts of resistance exercise (RE) completed at 3 relative intensities (RI). (2)To determine the relationship between external measures of Work & Power during RE & O2 uptake (VO2) & CO2 production (VCO2). METHODS: 9Ss, 7 female, who were RE untrained volunteered. Ss underwent assessments to determine VO2max, body composition (BodPod), & 1-RM for Chest Press (CP) & Leg Press (LP). RI were set at 33, 50, & 75% 1-RM; 22, 15, & 10 reps were performed, respectively, in an attempt to control for volume of work during RE. Experimental procedures consisted of: 5min Rest, followed by RE, & 10min Post RE Rest; RE & Post RE Rest were repeated for LP & CP at each RI. RE-RI combinations were counterbalanced. VO2, VCO2 & HR were recorded using a Cosmed K4b2. Work (W), Work Integral (IntW), Power (P), & Total RE Time (T) was measured with an ultrasound sensor (used to measure Distance & Time of weight stack movement) and NI’s Labview software platform. RESULTS: Age=21.5±0.5yrs, Ht=166.5±6.2cm, Mass=65.4±11.7kg, BMI=23.5±3.7, BodyFat%=20.7±7.5, FM=13.8±7.5kg, LM=51.5±7.7kg, VO2max=46.4±8.4ml/kg/min, RERmax=1.13±0.03, & HRmax=200±6.2. Total O2 cost (TVO2) was measured as the O2 used during RE & 10min Post RE Rest using Integral estimation of breath-by-breath intervals. W, IntW & P during LP & CP was not significantly different (sd) by RI. T during LP & CP was sd by RI [LP75<LP50<LP33 & CP75<CP50<CP33; p<0.005]. W, IntW & P for LP compared to CP at each RI was significantly greater (p<0.01). T during LP75 vs CP75 was not sd while T for LP vs CP was significantly greater at 50% & 33% RI (p<0.005). W & IntW for Rep1 vs last Rep were not sd for LP or CP by RI. P for Rep1 vs last Rep was sd for LP75 & CP75 (p<0.05). W, IntW & P were significantly, positively correlated with VO2 & VCO2 during RE for CP at each RI & for LP50. W, IntW & P for LP or CP were not correlated with TVO2. CONCLUSIONS: Measurement of W & P was actually held constant during RE bouts at each RI, but W & P during LP was greater at each RI. Only during CP were W & P related to VO2 & VCO2 at each RI; however, TVO2 was not related to W & P during either LP or CP. This suggests a disassociation between W & P and the dynamics of VO2, VCO2 & TVO2 and ultimately the O2 deficit & debt incurred during & following RE.