Cycling Cadence Alters Exercise Hemodynamics

Abstract

mmma Previous studies on cycling cadence have focused on the economy of the cadence. in search of the optimal pedal cadence. The purpose of this study was to determine the hemodynarnic changes associated with varylng pedal cadence at a constant workload. It was hypothesized that increased pedal cadence would enhance the skeletal muscle pump, resulting in elevation of cardiac output. Seven cycllsts were enlisted to cycle at 200 watts at pedal cadences of 70.90 and 110 rpm (random order). Oxygen uptake. heart rate. stroke volume, cardiac output. blood pressure. and vascular resistance were determined. As has been previously shown, oxygen uptake increased with increased cadence (70. 90. 110 rpm) at this workload. Heart rate. stroke volume. cardiac output and blood pressure were increased. and vascular resistance decreased, with increased cadence. Cardiac output increased (34 %)in excessof theincrease in oxygen uptake (15 %) as shown by the decrease (-14.5 %) in the arterial-venous oxygen difference occurring with increasing cadence. Apparently, even though the workload was constant, the increase in pedal cadence resulted in a more effective skeletal-muscle pump which increased muscle blood flow and venous return. It is not known if this might contribute to the natural selection of higher cadences by cycling athletes. even though there is reduced economy.a Key words: Pedal frequency, cardiac output, skeletal-muscle pump, cycling economy, cardiovascular l ntrod udion The cadence used by cyclists has been investigated as to the most efficient or economic pedal frequency required for performance (3.7.12.18,19,24). A non-linear reltionship appean to exist between oxygen uptake and pedal cadence (3). In general, investigations have indicated that oxygen uptake increases at pedal cadences both below and above an "optimum" pedal cadence during a constant workload (3,24). This "optimum" pedal cadence increases linearly with increasingworkInt.

Cortical Brain Activity is Influenced by Cadence in Cyclists

“…These findings are consistent with those of other studies [11,12,22,23]. Despite decreasing pedal forces the need to stabilize the upper body and the trunk area more at higher frequencies results in increased cardiac stress [24].…”

“…was also found in previous studies [11][12][13]27]. Furthermore, it is already known that blood lactate increases with higher cadences and work load [28,29].…”

“…These facts depend on the activation of fast-twitch muscle fibres in the exercise program [32]. Due to a higher heart rate with increasing cadence, some authors also state that a stronger and more efficient blood flow is elicited in stressed muscles, which causes an increased washout of lactate in the blood [11,23,25].…”

“…On the one hand cardiorespiratory and metabolic responses to varying movement frequencies were adequately investigated [11][12][13], but on the other hand the effect of different cadences on the central nervous system has not been studied so far during exercise. Therefore, the purpose of this study was to examine the influence of different cycling cadences on cortical brain activity, heart rate, blood lactate and perception of effort.…”

Cardiovascular and Metabolic Alterations in Mice Lacking Both β1- and β2-Adrenergic Receptors

“…The demonstration that humans under ␤-AR blockade can increase stroke volume via the Frank-Starling mechanism (while heart rate remains depressed) supports the idea that chronotropic and inotropic stimulation through ␤-ARs are not required for maximal exercise performance (45). Other studies have shown that during exercise, intrinsic mechanisms such as increased venous return enhances diastolic filling and hence cardiac output (46,47) and can be preferentially utilized over heart rate changes in some pathological states to maintain cardiac output (48). Together with our data in genetically altered mice, such results underscore the importance of intrinsic preload and afterload mechanisms and tend to mitigate the requirement for ␤-AR signaling in the adaptive responses to exercise.…”