Leg Muscle Activity and Perception of Effort before and after Four Short Sessions of Submaximal Eccentric Cycling

Abstract

Background: This study tested muscle activity (EMG) and perception of effort in eccentric (ECC) and concentric (CON) cycling before and after four sessions of both. Methods: Twelve volunteers naïve to ECC cycling attended the laboratory six times. On day 1, they performed a CON cycling peak power output (PPO) test. They then carried-out four sessions comprising two sets of 1 to 1.5-min cycling bouts at 5 intensities (30, 45, 60, 75, and 90% PPO) in ECC and CON cycling. On day 2 and day 6 (two weeks apart), EMG root mean square of the vastus lateralis (VL), rectus femoris (RF), biceps femoris (BF), and soleus (SOL) muscles, was averaged from 15 to 30 s within each 1-min bout and perception of effort was asked after 45 s. Results: Before the four cycling sessions, while VL EMG was lower in ECC than CON cycling, most variables were not different. Afterwards, ECC cycling exhibited lower RF EMG at 75 and 90% PPO (all p < 0.02), lower VL and BF EMG at all exercise intensities (all p < 0.02), and inferior SOL EMG (all p < 0.04) except at 45% PPO (p = 0.07). Perception of effort was lower in ECC cycling at all exercise intensities (all p < 0.03) but 60% PPO (p = 0.11). Conclusions: After four short sessions of ECC cycling, the activity of four leg muscles and perception of effort became lower in ECC than in CON cycling at most of five power outputs, while they were similar before.

Keywords: electromyography; familiarization; interindividual variability; semi-recumbent cycling.

Figure 1

Overview of the protocol. In panel A, each of the six squares represents a session in the laboratory. Measurements were carried out in eccentric and concentric cycling during the first set of the first session (PRE-test) and during the sixth session (POST-test). EMG of the rectus femoris, vastus lateralis, biceps femoris, and soleus muscles, as well as perceptions of effort and of the difficulty to pedal at the instructed cadence (60 rpm), were recorded. Panel B shows an example of a raw and unfiltered EMG signal (at PRE during CON cycling at 60% PPO), with the timing of physiological (EMG and heart rate) and perceptual measurements (perceived effort and difficulty to pedal at the instructed cadence). PPO: Peak power output; CON: concentric cycling; ECC: eccentric cycling.

Figure 2

Individual difference in EMG between concentric and eccentric cycling. This figure shows the difference (percentage point) in the root mean square of the EMG between CON and ECC cycling, averaged for all exercise intensities per muscle and per individual, before (PRE) and after (POST) the four sessions of cycling. Note that the scale of the abscissa differs for each chart. A negative score means that EMG RMS was greater in ECC than CON cycling. ^$: Difference between PRE and POST at a given power output (p < 0.05). Error bars represent the standard error.

Figure 3

Muscle activity. Panel A displays the scattered muscle activity (EMG RMS) of the rectus femoris (RF) muscle before (PRE) and after (POST) the four sessions of cycling. Panels B–D show the EMG RMS of the vastus lateralis (VL), biceps femoris (BF), and soleus (SOL) muscles, respectively. Data were normalized to the EMG RMS in CON cycling at 30% of the peak power output the same day. Only three exercise intensities are displayed for sake of clarity. Difference between CON and ECC cycling value at a given power output: * means p < 0.05; ** means p < 0.01. Error bars represent the standard error.

Figure 4

Heart rate and perceptual responses. Panel A represents the heart rate before (PRE) and after (POST) the four sessions of cycling. Panel B shows perceived effort, and panel C the perceived difficulty to pedal at the requested cadence (“motor control difficulty”). Only three exercise intensities are displayed for sake of clarity. Difference between CON and ECC cycling values at a given power output: * means p < 0.05; ** means p < 0.01. Error bars represent the standard error.