**2. Methods**

the timing of the single fibre action potentials. Thus the surface EMG reflects both peripheral and central properties of the neuromuscular system [4]. For many muscles, optimal firing rate, which is that elicited by a maximal voluntary effort, is sufficient to generate a fused tetanus in individual motor units. In predominantly fast-twitch muscles (e.g. biceps brachii), this firing rate is ~30Hz whereas in predominantly slow-twitch muscles (e.g. soleus), this firing rate is ~10Hz [5]. This electromyographic signature is warranted in order for the muscle to express its maximal force generating capabilities, and there have been many studies carried out that have reported a significant increase in agonist SEMG recordings following a resistance training program in both males and females, and in the young as well as the elderly [3, 6-12]. As mentioned previously, muscle adapts in a specific manner to the stimulus provided, and in the case of the aforementioned studies, increases in agonist muscle activation has been shown to be specific to the mode of muscular contraction employed during the resistance training period, and has been fairly well characterised. It is however unclear whether chronic changes

One aspect of resistance training that is scarcely reported in the literature is the acute (and/ or chronic) responses to resistance training programs whereby the length of the muscle when it is loaded is being manipulated. Acutely, it has been demonstrated that there are significantly different responses to exercising at different joint-angles (and thus different muscle lengths).

found that maximal muscle oxygen consumption was reached significantly later, and was on

found that when performing isometric contractions at 50% MVC to failure at either 50o or

present both when the exercise was performed with the local circulation occluded and not occluded, thereby highlighting local events as being key to the performance of the musculature at discrete knee angles (or muscle lengths). In addition to this, the slope of the iEMG-time to

that one of the reasons for an increase in oxygen consumption at longer muscle lengths (or more flexed joint angles) is that to produce the same external torque, the internal mechanical

because the moment arm of the in-series elastic component (i.e. the distance between the tendon and the joint centre of rotation, a factor which impacts on the forces required at the muscle) is shorter [16] at more flexed angles. The above studies provide compelling evidence of the link between the muscle length during a bout of resistance exercise and the acute impact on muscle activation levels, energetic provision, fatigability, as well as torque production. It has therefore been important to determine the nature of the acute effects of length-specific training because it is the accumulation of the acute responses that ultimately are reflected in

, 60o

; 199±22Nm, 30o

(298±41Nm). A subsequent study [14]

than 50o

and 90o knee flexion. Furthermore, Hisaeda et al.[15]

condition compared to 50o

) compared to extended angles (30o

, and 90o of knee

. This effect was

. It is proposed

 or 50o )

than the other

; 199±29Nm)

in the magnitude of the EMG signal occur with training.

De Ruiter et al. [13] showed that during isometric MVC exercise at 30o

of knee flexion, endurance time was significantly shorter at 90o

the chronic muscle adaptations (known as the repeated bout effect).

two angles, despite having identical torque production as 30o (90o

and significantly lower torque production than 60o

fatigue regression was significantly greater in the 90o

stress must be higher at more flexed angles (90o

average ~60% less at 30o compared to 60o

156 Electrodiagnosis in New Frontiers of Clinical Research

90o

flexion, maximal activation of the knee extensors was significantly greater at 90o
