During the exercise bouts conducted at 60% MPO, the maximal values of RER were 0.93 ± 0.02 in Y and 0.92 ± 0.02 in O, indicating a major contribution of aerobic pathways to energy expenditure.
The effect of cadence and power output on GE in the two study groups is depicted in Figure 2. At all pedal rates and at both levels of power output, GE was higher in Y than that in O (P < 0.01).
GE was significantly influenced by pedaling cadence (F = 137, P < 0.0001), and this effect was different in Y versus O (F = 7.772, P < 0.01).
The cadence resulting in the highest value of GE was 60 rpm in Y, whereas in O GE at 40 and 60 rpm was not significantly different. This trend was observed at both levels of power (60% and 40% MPO).
From 60 to 120 rpm and at 40% MPO, GE decreased by 21% ± 5% in Y and by 30% ± 5% in O (P < 0.01). The difference between groups in the reduction of GE when increasing cadence from 60 to 120 rpm was even more pronounced at 60% MPO (11% ± 3% in Y and 23% ± 5% in O) and was meaningful, as indicated by an effect size of 1.8 and 2.6 at 40% and 60% of MPO, respectively.
With the increase in power output, GE increased in both groups and at all pedaling rates. Peak efficiency (at 60 rpm) increased from 21.2% ± 1.9% to 23.7% ± 1.8% in Y and from 18.3% ± 0.6 % to 20.7% ± 1.7 % in O.
A significant interaction between cadence and power output was found (F = 3.225, P = 0.016). This was evident as an attenuation of the reducing effect of high cadences on GE (difference between 60 and 120 rpm), which was, however, more pronounced in Y than that in O (P < 0.05).
Figure 3 shows the mean fractional utilization of V˙O2max as a function of cadence. From 60 to 120 rpm, relative exercise intensity increased by 9% ± 2% in Y and 22% ± 6% in O (P < 0.001) and by 4% ± 4 % in Y and 18% ± 5% in O (P < 0.001) at 40% and 60% MPO, respectively.
In the present study, we investigated cycling GE differences between young and older cyclists, with a special emphasis on verifying the effect of adopting different pedaling rates. The main findings were a) a lower cycling efficiency at the same relative workload in O than that in Y for a wide spectrum of cadences, b) a lower freely chosen pedal rate and most efficient cadence in O than that in Y, and c) a higher reduction in GE with the increase in pedaling rate in O than that in Y. This effect was attenuated by the increase in power output more in Y than that in O.
Among the different factors affecting cycling endurance performance, those resulting in a high mechanical efficiency are considered to play a key role (15). Despite thorough investigation of cycling efficiency in young volunteers, there is a paucity of data concerning older individuals, athletes either trained or untrained. Most of the studies available on efficiency in master athletes have been performed in runners and suggest that running economy may be similar between young and older athletes (29). However, running economy and cycling efficiency are influenced by different factors, such as the capacity of the muscles to store and release elastic energy in the former (35) or the possibility of modulating the force exerted at a given power output using different cadences in the latter (26).
In the present study, we found a lower GE in O than that in Y at the same relative workload for a wide spectrum of cadences. To date, few studies have examined cycling efficiency in older individuals, with a variety of populations investigated. Peiffer et al. (31) reported a similar cycling economy in master cyclists of different ages. However, in that study, cadence was not controlled, subjects were only tested at the same absolute workload, and the caloric equivalent of V˙O2 at a given RER was not considered. These factors make the comparison with the results of the present study very difficult. Conversely, Bell and Ferguson (4) recently measured cycling efficiency at different cadences in older and young women and found, in agreement with the present results, a trend for a lower efficiency at same relative workload in the former. Conversely, Astrand (3) reported a similar cycling efficiency irrespective of age. On the other hand, it should be recognized that the choice of the cadence and the power output used to test cycling efficiency in the different studies represent a critical issue and make the comparison very difficult. Moreover, because of the effect of power output on efficiency and the lower absolute power output used in the older cyclists, we cannot rule out the possibility of a similar efficiency when testing the two groups at the same absolute workload.
To the best of our knowledge and in contrast to the plethora of data available in younger cyclists, no studies have investigated the relation between pedaling rate and GE in older cyclists.
The most efficient cadence recorded in our younger cyclists was within the range (60-80 rpm) previously reported (5,8,14). Moreover, in accordance with previous observations in young individuals (7,32), GE decreased with the increase in cadence, both in Y and in O. However, despite a similar trend, GE in O peaked already at 40 rpm whereas was maximal at 60 rpm in Y. These results are in line with Bell and Ferguson's (4) observations in young and elderly untrained women and suggest a shift of the most efficient cadence toward lower values with aging. Furthermore, the decline in GE at high cadences was steeper in O than that in Y, indicating a lower advantage of the older cyclists in using shorter gears, that is, those resulting in shorter distances covered in each pedal cycle, for a given speed.
With regard to the relationship between efficiency and FCC, several investigations indicated that young cyclists normally choose to pedal on the road at higher cadences (27,34) than those resulting as the most efficient in the laboratory setting (5,7,8,16,18,28,32,37). In contrast, despite the common observation that older cyclists pedal on the road at lower rates than their younger training companions, this has never been translated into scientific evidence. We found that FCC throughout the incremental maximal cycling test was nearly constant in both groups but was significantly lower in O than that in Y. On the basis of a recent report (25), we cannot rule out that using cadence and gears to control the work rate instead of relying on a fixed power output maintained independently of cadence would have resulted in a different trend in FCC during the incremental test; however, the divergence discovered in the absolute FCC values between Y and O remains. The present data, therefore, raise the possibility that the peculiarity of the cadence-efficiency relationship in O may be linked to their lower FCC.
An interesting observation of the present study is the different effect of the increase in cadence on the fractional utilization of V˙O2max in Y versus O. A significant difference in efficiency was found at 40 rpm and both at 40% and 60% MPO when the two groups were exercising at exactly the same relative intensity. At all other cadences (especially at 100 and 120 rpm), O were pedaling at a higher %V˙O2max. The higher increase in relative workload with the increase in pedaling rate in the older cyclists implies that cadence has a different effect on endurance performance potential with respect to the young.
It is possible that young cyclists with a higher V˙O2max do not necessarily have to try to maximize efficiency because a greater metabolic power output at higher cadences may be more relevant to performance than the concomitant, but marginal, decrease in efficiency. The situation is likely to be very different for the master cyclists who respond to an increase in cadence with a higher metabolic cost and possess a more limited maximal aerobic power. Therefore, for the older cyclist, pedaling outside of the most efficient cadence range may be much more demanding and detrimental to performance than for young athletes. This might explain the choice of older cyclists to pedal at lower rates than their younger counterpart. Indeed, the pronounced effect of even small variations in GE on cycling performance has been previously highlighted in relation to time trials (22,30) or to performance changes throughout the same (20) or several competitive seasons (10,33). From this point of view, the differences in GE between groups and with cadence appear relevant for performance.
In accordance with previous reports in young cyclists (7,17,32), in the present study the increase in power output resulted in a higher GE at all cadences in both Y and O. However, whereas the reduction in efficiency from 60 to 120 rpm was attenuated with the increase in power in young cyclists, this was less evident (about half) in older cyclists (7,32).
A proposed explanation for the reduction of the cadence effect at high power outputs is that the cost of moving the legs with a high frequency represents a lower proportion of the total energy expenditure (32). Along this line, it is possible to speculate that the cost of moving the legs could be more influential in O than that in Y because of their lower maximal aerobic power. This was reflected also in the observed higher increase in the fractional utilization of V˙O2max with cadence in O than that in Y at the lower level of power output.
In addition, a difference in the share of noneffective forces with the increase in power output cannot be excluded because it has been reported to lessen with the increase in power output in young (38). Finally, the increase in the cost for stabilizing the upper body at the higher cadences (19) and power outputs might differ between Y and O. Taken together, these data suggest that O cyclists, differently from Y, would not benefit from pedaling at high pedaling rates when riding at higher power outputs. Hence, the choice of using a given cadence to minimize energy expenditure appears more crucial for young than for older cyclists.
In conclusion, the results of the present study indicate that GE is lower in older than that in young cyclists when pedaling at the same relative intensities and for a wide spectrum of cadences. The increase in pedaling rate reduces GE more in older than that in young cyclists, and it is metabolically more demanding in the former than that in the latter. Moreover, the increase in power output mitigates the effect of higher cadences in reducing GE more in young and less in older cyclists. In addition, older cyclists are most efficient at a lower cadence than the young ones.
Taken together, these data suggest that controlling cadence is more crucial for older than for the young cyclists and may help explain why the former choose to pedal at lower rates than the latter.
The study was supported by the Università degli studi di Roma Foro Italico (grant No. N.250-07).
The results of the present study do not constitute endorsement by the American College of Sports Medicine.
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Keywords:©2010The American College of Sports Medicine
MASTER ATHLETE; PEDAL RATE; FREELY CHOSEN PEDAL RATE; CADENCE-EFFICIENCY RELATIONSHIP; AGING