A PSYCHOBIOLOGICAL APPROACH TO IMPROVE EXERCISE ADHERENCE

Study I Rating of perceived exertion (RPE) is a negative determinant of physical activity. This conscious sensation is related to the intensity of the performed task. It is well known that high-intensity exercise is associated to a lower rate of adherence when compared to a moderate intensity regimen. Caffeine is one of the most widely used drugs in the world. Furthermore, it has been well established that it can enhances performance in athletes either by a higher power production. The effect of caffeine on RPE in unfit people is poorly understood and controversial. It has been suggested that RPE could be not affected by caffeine in this population during a sub-maximal aerobic exercise. The aim of this study was to establish whether caffeine affects RPE in sedentary healthy subjects during a sub-maximal aerobic exercise. A secondary aim was to determine the effects of caffeine on cardiovascular and physiological variables. 16 healthy subjects were involved in the study. In this randomised cross-over study participants visited the laboratory four times. After a VO2MAX determination each subject was asked to perform a sub-maximal aerobic simulation taking in a randomised order 400,200mg and placebo. There was a significant treatment x workload interaction of caffeine on RPE(p<0.05,p=0.006). Pairwises comparisons indicated that a dosage of 200 mg(M=15.66,SD=1.69)(p<0.05,p=0.014) and 400mg (M=15.47,SD=1.26)(p<0.05,p=0.000) of caffeine were significantly different in reducing RPE compared to placebo (M=16.94,SD=1.94). No significant differences were found between the 200,400mg of caffeine(p=1.000). No significant treatment x workload interaction was found on VO2(p=0.480). There was a significant main effect of workload on VO2 on the three different conditions(p<0.05,p=0.000). No treatment x workload interaction on VCO2(p=0.408). Significant main effect of workload(p<0.05,p=0.000) was found. No treatment x workload interaction on VE(p=0.388). Significant main effect of workload(p<0.05,p=0.000) was found. No treatment x workload interaction on HR(p=0.548). Significant main effect of workload (p<0.05,p=0.000) was found. No treatment x workload interaction on La(p=0.390). Significant main effect of workload (p<0.05,p=0.045). No treatment x workload interaction on RPM(p=0.659). A significant main effect of workload(p<0.05,p=0.004) was found. No significant treatment x workload interaction on SV(p=0.284). A significant main effect of workload(p<0.05,p=0.049) was found. No significant treatment x workload interaction on CO(p=0.285). A significant main effect of workload (p<0.05,p=0.001) was found. No significant treatment x workload interaction on SBP (p=0.538) A significant main effect of workload(p<0.05,p=0.001) was found. No significant treatment x workload interaction on DBP(p=0.972). There was not any significant main effect of workload(p= .194). In conclusion, this study demonstrated that 200 mg of caffeine taken on a chewing-gum based pill 15 minutes before a sub-maximal aerobic exercise were able to reduce RPE in sedentary individuals. STUDY II: It is well known that physical activity improves physical fitness and several health outcomes whether performed on a regular basis, at the right intensity, duration and frequency. As reviewed by Dishman physical activity behaviour is determined by several factors. Previous studies on exercise adherence have been focused on psychological and behavioural interventions in order to improve this behaviour. To date, there are just few studies that used nutritional strategies in order to improve exercise adherence. The aim of the study was to implement in a randomized controlled trial a 3 times per week for 12 weeks aerobic training in order to test the hypothesis that 200 mg of caffeine assumed before each training session could increase the adherence to a vigorous aerobic training program. After randomization, subjects performed a VO2 MAX in order to define the PPO [W] and training intensities for the first 6 weeks of training. Same procedures for the mid-test and post-test. Was also asked to each subject to perform a baseline mid and post-test assessment of IPAQ, EMI-2 and BRUMS questionnaires in order to detect any difference on the general level of physical activity during daily activities and on mood and motivation. Adherence parameters were measured at 6 and 12 weeks of training in order to detect differences between caffeine and placebo group. Subjects visited the gym 3 times/week for 12 weeks. Results: Attendance to the exercise program were significantly different on the weeks 1 to 6 [CAF(12.92±3.75)PLAC(15.92± 2.54)t(23)=-2.99,p=0.030],6 to 12 [CAF(4.00±5.34) PLAC(8.67 ± 5.34) t(23) =-4.67,p= 0.040] and all the 12 weeks of training [CAF(16.92 ± 7.98)PLAC(24.58±6.49)t(23)=-7.66,p=0.040].The mean percentage of time completed was significantly different on the weeks 1 to 6 [CAF(68.01±19.46)PLAC(85.50±14.19) t(23) =-17.49,p=0. 018] and from week 1 to 12 [CAF(47.01 ± 22.18)PLAC(68.29 ± 18.02) t(23) = -21.28, p = 0.015]. The comparison of mean total time performed for each training was found significantly different at session 12,15,17,21,22,33,35(P<0,05). Results on BRUMS questionnaire did not reveal any significant treatment x time interaction between caf_pre and plac_pre compared to caf_post and plac_post on ANGER(p=0.700), CONFUSION(p= 0.976),DEPRESSION(p=0.807),FATIGUE(p=0.700),TENSION(p=0.582) and VIGOUR(p =0.867). Furthermore, there was not found any main effect of time for each tested variable (P>0,05). The EMI2 results did not show any interaction between the pre–post test comparisons between caf and plac groups on AFFILIATION(p = 0.370),APPEARANCE(p =0.685),ENJOYMENT(p = 0.643),HEALTHPRESSURE(p = 0.855),HILLHEALTH AVOIDANCE(p=0.394),NIMBLENESS(p=0.597),POSITIVEHEALTH(p=0.227), REVITALISATION(p=0.324),SOCIALRECOGNITION(p=0.364),STRENGTHENDURANCE(p=0.696)and WEIGHTMANAGEMENT(p=0.929). A significant main effect of time was found on AFFILIATION,POSITIVEHEALTH (P<0.05), whilst for all the other EMI-2 tested variables was not found any main effect of time (P >0.05). PACES scale results did not show any significant interaction between caf and plac on PACESSCALESCORING(p=0.794). No main effect of time (p= 0.095). The IPAQ results presented a significant treatment x workload interaction on the pre-post comparisons between caf and plac on IPAQHIGHINTENSITYDAYS (p< 0.05,p= 0.028),IPAQHIGHINTENSITYMINUTES(P<0.05,p=0.014). On the other hand, all the other parameters, like IPAQMODERATEINTENSITYDAYS(p=0.374),IPAQ MODERATEINTENSITYMINUTES(p=0.594),IPAQWALKINGDAYS(p=0.647),IPAQ WALKINGMINUTES(p=0.898) and IPAQSEATEDMINUTES(p=0.898) did not present any significant interaction (P>0.05). Main effect of time was found significantly different for IPAQHIGHINTENSITYDAYS,IPAQHIGHINTENSITYMINUTES (P<0.05) PHYSIOLOGICAL PARAMETERS: The pre-post test analysis of the PPO did not show a significant treatment x workload interaction between caf and plac (p = 0.683). Significant main effect of time (P<0.05)(p = 0.003). ANOVAs performed on VO2 PEAK and HR pre-post test did not reveal a significant treatment x workload interaction (VO2 PEAK (p = 0.462), HR (p = 0.856)). Significant main effect of time for HR (p< 0.05, p = 0.001). The data analysis of RPE pre-post test comparing caf and plac groups, did not reveal a significant difference accounted for the effort perceived during each training sessions (p = 0.487). Significant main effect of time(p< 0.05,p=0.001). All the data are presented by mean±SD. Conclusions: This study demonstrated that there is not any effect of caffeine on perception of effort and adherence improvement in sedentary subjects. From a physiological point of view, due to a reduction in total time of training and percentage of total training completed we do not have demonstrated an improvement in aerobic fitness. On the other hand, adherence for the placebo group was significantly different compared to caffeine.