Freely Chosen Cadence is Increased during Repeated Bouts of Submaximal Ergometer Pedalling.

It was investigated whether the phenomenon of repeated bout rate enhancement occurs during submaximal ergometer cycling. Repeated bout rate enhancement is defined as an increase of the freely, or spontaneously, chosen cadence during repeated bouts of pedalling and has previously been reported for finger tapping. This is relevant to study since cadence can affect biomechanical and physiological responses. Recreationally active individuals (n=27) performed five consecutive 5-min bouts of cycling at 100 W using freely chosen cadence. All bouts were separated by 10-min rest. Cadence, pedal force profile characteristics, heart rate, tympanic temperature, and rate of perceived exertion were determined during cycling. The primary result was that cadence at the end of 5. bout was statistically significantly higher than at the end of all other bouts. Overall, the cadence at the end of 5. bout was 15.6%±20.4% higher than at the end of 1. bout. The altered rhythmic motor behaviour was accompanied by a statistically significant effect of bout on the pedal force profile. Also, there was a statistically significant effect of bout on heart rate, which amounted to 125±17 and 131±26 beats/min at the end of 1. and 5. bout, respectively. Perhaps the observed increase of cadence occurred as a nonconscious rhythmogenesis process in form of a net excitation of relevant parts of the nervous system. In conclusion, repeated bout rate enhancement during submaximal ergometer cycling occurred. The freely chosen cadence showed an increase of on average about 15%, or 10 rpm, as accumulated values across five bouts of cycling.

On voluntary rhythmic leg movement behaviour and control during pedalling.

The overall purpose of the present dissertation was to contribute to the understanding of voluntary human rhythmic leg movement behaviour and control. This was achieved by applying pedalling as a movement model and exposing healthy and recreationally active individuals as well as trained cyclists to for example cardiopulmonary and mechanical loading, fatiguing exercise, and heavy strength training. As a part of the background, the effect of pedalling frequency on diverse relevant biomechanical, physiological, and psychophysiological variables as well as on performance was initially explored. Freely chosen pedalling frequency is considerably higher than the energetically optimal pedalling frequency. This has been shown by others and was confirmed in the present work. As a result, pedal force is relatively low while rates of VO2 and energy turnover are relatively high during freely chosen pedalling as compared to a condition where a lower and more efficient pedalling frequency is imposed. The freely chosen pedalling frequency was in the present work, and by others, found to most likely be less advantageous than the lower energetically optimal pedalling frequency with respect to performance during intensive cycling following prolonged submaximal cycling. This stimulates the motivation to understand the behaviour and control of the freely chosen pedalling frequency during cycling. Freely chosen pedalling frequency was in the present work shown to be highly individual. In addition, the pedalling frequency was shown to be steady in a longitudinal perspective across 12 weeks. Further, it was shown to be unaffected by both fatiguing hip extension exercise and hip flexion exercise as well as by increased loading on the cardiopulmonary system at constant mechanical loading, and vice versa. Based on this, the freely chosen pedalling frequency is considered to be characterised as a highly individual, steady, and robust innate voluntary motor rhythm under primary influence of central pattern generators. The last part of the characterisation is largely based on, and supported by, work of other researchers in the field. Despite the robustness of the freely chosen pedalling frequency, it may be affected by some particular factors. As an example from the present work, freely chosen pedalling frequency during treadmill cycling increased by on average 15 to 17 rpm when power output was increased from a value corresponding to 86% and up to 165% of Wmax . This phenomenon is supported by other studies. As another example from the present work, freely chosen pedalling frequency decreased by on average 9 to 14 rpm following heavy strength training that involved both hip extension and hip flexion. Further, the present work suggested that the latter phenomenon occurred within the first week of training and was caused by in particular the hip extension strength training rather than the hip flexion strength training. The fast response to the strength training indicated that neural adaptations presumably caused the observed changes in movement behaviour. The internal organisation of the central pattern generator is by some other researchers in the field considered to be functionally separated into two components, in which, one is responsible for movement frequency and another is responsible for movement pattern. For the present dissertation, the freely chosen pedalling frequency was considered to reflect the rhythmic movement frequency of the voluntary rhythmic leg movement of pedalling. The tangential pedal force profile was considered to reflect the rhythmic movement pattern. The present work showed that fatiguing hip flexion exercise in healthy and recreationally active individuals modified the tangential pedal force profile during cycling at a pre-set target pedalling frequency in a way that the minimum tangential pedal force became more negative, the maximum tangential pedal force increased, and the phase with negative tangential pedal force increased. In other words, the legs were "actively lifted" to a lesser extent in the upstroke phase. Fatiguing hip extension exercise did not have that effect. And none of the fatiguing exercises affected the freely chosen pedalling frequency. The present work furthermore showed that the primary effect of hip extension strength training was that it decreased the freely chosen pedalling frequency. An interpretation of this could be that the hip extension strength training, in particular, influenced the output from the component of the central pattern generator that may be responsible for rhythmic movement frequency.