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The purpose of this investigation was to describe the just noticeable difference (JND) in perceived exertion during cycle exercise. Males ( n = 20) and females ( n = 26) (21.4 ± 3.1 year) performed load-incremented cycle exercise to peak intensity. At the end of each minute, subjects rated their overall-body perceived exertion using the OMNI (0-10) rating of perceived exertion (RPE) scale. Individual regression derived the power output (PO) corresponding to RPE 5. This PO served as the standard stimulus (SS). On a separate occasion, four 5-min cycling bouts were performed with 5 min rest between bouts. During bouts 1 and 3 subjects cycled at the SS. During bouts 2 and 4 subjects adjusted the resistance to achieve a level of exertion just noticeably above/below the SS. The difference in final 30-s oxygen consumption ( VO) and PO between each JND bout and the previous SS were the above (JND-A) and below (JND-B) perceived exertion JNDs. JND-A and JND-B were compared between genders and between subjects exhibiting lower versus higher ventilatory threshold (VT) and VO within genders for VO (l·min, % VO) and PO (W, %SS). JND-B was significantly ( P < 0.05) greater than JND-A for VO and PO, when expressed in absolute (l·min, W) and relative units (% VO, %SS). Males exhibited greater JND values than females in absolute, but not relative, units. Subjects with lower and higher VT and VO exhibited similar JND values. The JND can serve as an effective tool to measure perceptual acuity and to determine individual ability to self-regulate prescribed exercise intensities. [ABSTRACT FROM AUTHOR]

This study examined whether critical power (CP) in adolescents: (1) provides a landmark for maximal steady-state exercise; and (2) can be determined using 'all-out' exercise. Nine active 14-15 year olds (6 females, 3 males) performed five cycling tests: (1) a ramp test to determine $$ \dot{V}{\text{O}}_{{2\,{\text{peak}}}} $$; (2) up to four constant power output tests to determine CP; (3-4) constant power output exercise 10% above and 10% below CP; and (5) a 3 min all-out cycle test to establish the end power (EP) at 90 and 180 s of exercise. All participants completed 30 min of exercise below CP and were characterized by steady-state blood lactate and $$ {\dot{V}\text{O}}_{2} $$ profiles. In contrast, time to exhaustion during exercise above CP was 15.0 ± 7.0 min and characterized by an inexorable rise in blood lactate and a rise, stabilization (~91% $$ {\dot{V}\text{O}}_{{2\,{\text{peak}}}} $$) and fall in $$ {\dot{V}\text{O}}_{2} $$ (~82% $$ {\dot{V}\text{O}}_{{2\,{\text{peak}}}} $$) prior to exhaustion. Eight out of nine participants completed the 3 min test and their EPs at 90 s (148 ± 29 W) and 180 s (146 ± 30 W) were not different from CP (146 ± 27 W) ( P = 0.98). The typical error of estimates for establishing CP using EP at 90 s or 180 s of the 3 min test were 25 W (19.7% CV) and 25 W (19.6% CV), respectively. CP in active adolescence provides a valid landmark for maximal steady-state exercise, although its estimation on an individual level using the 3 min all-out test may be of limited value. [ABSTRACT FROM AUTHOR]

A bout of eccentric exercise confers protection against subsequent bouts of the same exercise. This study investigated whether the protective effect would be produced similarly between old and young adults. Eight old men (70.5 ± 4.1 years) and ten young men (20.4 ± 2.0 years) performed two bouts of eccentric exercise of the elbow flexors (six sets of five eccentric actions) separated by 4 weeks. Changes in maximal isometric strength, range of motion (ROM), upper arm circumference (CIR), plasma creatine kinase (CK) activity, myoglobin (Mb) concentration, and muscle soreness (SOR) before, immediately after, and 1, 24, 48, 72 and 96 h following exercise were compared between bouts, and between groups by a two-way repeated measures ANOVA. Changes in the measures following the first bout were significantly ( P < 0.05) smaller for the old than the young group. The young group showed significantly ( P < 0.05) smaller changes in all measures following the second bout than the first bout; however, the old group had the protective effect only for ROM, Mb, and SOR. The magnitude of the effect observed for ROM and Mb concentration in the old group was significantly ( P < 0.05) smaller compared with that of the young group. These results suggest that the protective effect conferred by the first bout was less for the old than the young group. This may be due to the less muscle damage after the first bout in the old subjects, but it is also possible that the protective effect of old adults does not last as long as that of young adults. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to test the hypothesis that daily physical activity over a period of 15 years has been beneficial to aerobic fitness in young male and female participants (13-27 years) in the Amsterdam Growth and Health Longitudinal Study. Only subjects with the maximal data of six sets of measurements were included (83 male and 98 female participants). Daily physical activity was assessed using a standardized interview on activity and expressed as a weighted activity score. Aerobic fitness was assessed using a maximal running test on a treadmill and measuring the maximal oxygen uptake (VO2max) and the maximal slope of the track (Smax) To assess the longitudinal relationship between daily physical activity and aerobic fitness a real longitudinal analysis was carried out with generalized estimating equations, adjusting for differences in initial aerobic fitness at age 13, and for other lifestyle (dietary intake, smoking and alcohol consumption) and biological parameters (biological age, body fat, blood pressure and concentration of serum cholesterol). A significant relationship (P < 0.01) was observed between daily physical activity and both VO2max and Smax. It can be concluded that the development of aerobic fitness between the age of 13 and 27 years is independently and positively related to daily physical activity in this group of male and female participants in the study. The functional implications, however, are small: a relatively high increase in the weighted physical activity score of 30% over a period of 15 years results in a 2%-5% increase in aerobic fitness. [ABSTRACT FROM AUTHOR]