**3. Results**

#### **3.1. Acute responses**

*Muscle Activation*; As expected *Vastus lateralis* activation increased linearly with absolute external load, with activation being significantly greater (P<0.05) when lifting 40Kg compared to 20Kg, and also when lifting 60Kg compared to 40Kg (P<0.05) and 20Kg (P<0.001). When comparing activation between ranges-of-motion as a percentage of MVC, activation of the muscle was significantly (P<0.05) less at SL (59±6%, 63±7%) compared to LL (73±7%, 77±5) and LX (70±7%, 75±6%) at 40Kg and 60Kg loads respectively (Figure 2A). During relative loading, performing exercise at 60% 1RM did not increase activation compared to 40% 1RM (P>0.05), though activation was increased at 80% 1RM compared to 60% (P<0.05), and 40% (P<0.001). There were no significant differences in activation at 40% and 60% 1RM between the three ranges-of-motion (P>0.05), whilst at 80% 1RM, VL activation was significantly greater during exercise in LL and LX compared to SL (Figure 2B; P<0.05). It is notable that these effects were similar for all two 'long muscle' training protocols so that there were no significant differences between the longer muscle length ROM and the complete ROM under any loading conditions (P>0.05).

however there were no significant differences between LL and LX, or SL and LX at this loading

**Figure 2.** Vastus Lateralis activation in SL (black bars), LL (white bars) and LX (grey bars) following varying magnitudes

40 60 80

**Relative Load (% 1RM)**

20 40 60

\* \* <sup>A</sup>

**Absolute Load (Kg)**

\*

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Heart rate & Blood Pressure; There was a significantly greater (P<0.05) mean heart rate difference between LL (139±10 beats per minute) and LX (136±11bpm) compared to SL (118±12bpm) in both absolute and relative loading conditions, with no difference between LL and LX (P>0.05). Mean systolic blood pressure yielded no significant differences (P>0.05) between the three ROMs under relative loading conditions, however LX (148±8 mmHg) mean systolic blood pressure was significantly greater than both SL (138±6 mmHg) and LL (135±8

Agonist (VL) Muscle Activation; Figures 4 and 5 shows absolute (i.e. raw RMS\_EMG signal) and relative (i.e. RMS\_EMG normalised for values at baseline) changes in muscle activation at baseline and post-training. At week 8, absolute maximal agonist activation did not appear

mmHg) following loading under absolute loads (P<0.05).

**3.2. Prolonged resistance training responses**

B

of absolute and relative loading. \* Significantly different to SL

**VL Activation (% MVC)**

**VL Activation (% MVC)**

intensity (P>0.05).

Oxygen Consumption (VO2); There was no significant changes in VO2 between any of the absolute loading conditions or between any ROM (P>0.05). Furthermore, in the relative loading conditions, mean VO2 was significantly greater at 80% 1RM compared to 40% 1RM (6.4±0.9 ml/kg-1/min-1 vs. 9.93±1.3 ml/kg-1/min-1, P<0.05). VO2 was greater at 40% and 60% 1RM in LL and LX than SL, however there were no significant differences between these ROMs. At 80% 1RM there was a significantly greater VO2 (Figure 3) in the LL ROM compared to SL (P<0.05), How Deep Should You Squat to Maximise a Holistic Training Response?... http://dx.doi.org/10.5772/56386 161

**Figure 2.** Vastus Lateralis activation in SL (black bars), LL (white bars) and LX (grey bars) following varying magnitudes of absolute and relative loading. \* Significantly different to SL

however there were no significant differences between LL and LX, or SL and LX at this loading intensity (P>0.05).

Heart rate & Blood Pressure; There was a significantly greater (P<0.05) mean heart rate difference between LL (139±10 beats per minute) and LX (136±11bpm) compared to SL (118±12bpm) in both absolute and relative loading conditions, with no difference between LL and LX (P>0.05). Mean systolic blood pressure yielded no significant differences (P>0.05) between the three ROMs under relative loading conditions, however LX (148±8 mmHg) mean systolic blood pressure was significantly greater than both SL (138±6 mmHg) and LL (135±8 mmHg) following loading under absolute loads (P<0.05).

#### **3.2. Prolonged resistance training responses**

femoris was also recorded during graded maximal contractions in order to assess antagonist

*Resistance Training Program (RT)*; RT was carried out 3 days per week for 8 weeks and ceased during the 4 week detraining period. RT included performing 3-4 sets of 8-12 reps (depending on the stage of the training program) of exercises designed to overload the knee extensors muscle group. Exercises included the barbell back squat, leg extension, leg press, Bulgarian split squat, and forward lunge. 1RMs were assessed and recorded every two weeks to progress

*Muscle size measurements*; VL muscle widths were measured using B-mode ultrasonography (AU5, Esaote Biomedica, Italy) at 25%, 50% and 75% of femur length. The ultrasound probe was held in the transverse plane and used to locate the borders of either side of the VL muscle. Each of these junctures was marked on the skin and the distance between them measured. In addition, at each of the aforementioned sites, thigh girths were also measured using standard anthropometric techniques. All data is presented as mean ± standard deviation (S.D.).

*Muscle strength measurements*; Throughout the training program, 1RM of the knee extensors

*Muscle Activation*; As expected *Vastus lateralis* activation increased linearly with absolute external load, with activation being significantly greater (P<0.05) when lifting 40Kg compared to 20Kg, and also when lifting 60Kg compared to 40Kg (P<0.05) and 20Kg (P<0.001). When comparing activation between ranges-of-motion as a percentage of MVC, activation of the muscle was significantly (P<0.05) less at SL (59±6%, 63±7%) compared to LL (73±7%, 77±5) and LX (70±7%, 75±6%) at 40Kg and 60Kg loads respectively (Figure 2A). During relative loading, performing exercise at 60% 1RM did not increase activation compared to 40% 1RM (P>0.05), though activation was increased at 80% 1RM compared to 60% (P<0.05), and 40% (P<0.001). There were no significant differences in activation at 40% and 60% 1RM between the three ranges-of-motion (P>0.05), whilst at 80% 1RM, VL activation was significantly greater during exercise in LL and LX compared to SL (Figure 2B; P<0.05). It is notable that these effects were similar for all two 'long muscle' training protocols so that there were no significant differences between the longer muscle length ROM and the complete ROM under any loading conditions

Oxygen Consumption (VO2); There was no significant changes in VO2 between any of the absolute loading conditions or between any ROM (P>0.05). Furthermore, in the relative loading conditions, mean VO2 was significantly greater at 80% 1RM compared to 40% 1RM (6.4±0.9 ml/kg-1/min-1 vs. 9.93±1.3 ml/kg-1/min-1, P<0.05). VO2 was greater at 40% and 60% 1RM in LL and LX than SL, however there were no significant differences between these ROMs. At 80% 1RM there was a significantly greater VO2 (Figure 3) in the LL ROM compared to SL (P<0.05),

systematically monitored on a knee extension machine (Technogym, Bracknell, UK).

muscle co-activation.

160 Electrodiagnosis in New Frontiers of Clinical Research

the exercise loads.

**3. Results**

(P>0.05).

**3.1. Acute responses**

Agonist (VL) Muscle Activation; Figures 4 and 5 shows absolute (i.e. raw RMS\_EMG signal) and relative (i.e. RMS\_EMG normalised for values at baseline) changes in muscle activation at baseline and post-training. At week 8, absolute maximal agonist activation did not appear

post-training or following detraining at 25% and 50% femur length (SL; 12±13%, LL; 11±7%, LX; 13±11%). However, LL and LX groups had a greater significant (P<0.05) relative increase in muscle width at week 10 (LL; 26±13%, LX; 21±9%) compared to SL (13±8%) at 75% femur length. This was also the case at week 12, however only LL group was significantly greater (P<0.05) than SL group at this measurement site. Thigh girths increased following training at week 8 in all training groups and at all sites (mean over three sites SL; 3±2%, LL; 4±3%; LX; 4±2%), however this was not significantly different to baseline values (P>0.05) with no differences between groups. Thigh girths also did not differ significantly at weeks 10 or 12

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**Figure 4.** Absolute Changes in VL activation at baseline (pre) and week 8 (post) training at 50o (black bars), 70o (white

bars) and 90o (grey bars) knee flexion in A) SL, B) LX and C) LL groups.

compared to baseline or between groups.

**Figure 3.** Oxygen consumption (VO2) during relative loading in SL (black bars), LL (white bars) and LX (grey bars). \* Significantly different to 40% 1RM. # Significantly different to SL.

to increase significantly in chronic response to the training protocols, with no significant difference between training groups at any knee angle (P>0.05, Figure 4). However, on further investigation, it was found that in fact, post-training there was a significant relative increase in activation at 50o (23±15%, P<0.05), 70o (26±15%, P<0.01) and 90o (16±13%, P<0.05) in the LX group and at 70o (24±9%, P<0.01) and 90o (25±9%, P<0.01) in LL group. In the SL group there was no significant change at 50o , although there were significant (P<0.05) reductions in VL activation at both 70o (-15±6%) and 90o (-13±5%). Following detraining, muscle activation at 70o decreased at week 10, and levelled off for the remainder of the detraining period (week 12) in both LL and LX groups with no significant changes compared to week 8. In the SL group, activation reduced at both weeks 8, 10 and 12 compared to baseline, however despite larger decrements in this group, there was no significant differences between all three training groups (Figure 6, P>0.05).

*Muscle widths and thigh girths*; Changes in muscle widths are shown in Table 1. At week 8, VL muscle widths had increased significantly at all three measurement locations in all training groups compared to baseline (P<0.001). Following the first period of detraining at week 10, the SL group had returned to baseline values at all three measurement sites (P>0.05), however both LL and LX groups retained adaptations at this juncture relative to baseline (P<0.01). At week 12 LX group had returned to baseline levels at 25% and 50% width but still remained signifi‐ cantly hypertrophied at 75% femur length compared to baseline (P<0.05). The LL group retained their significant gains in muscle width at all three sites for the duration of detraining (P<0.01). There were no significant (P>0.05) mean relative changes between training groups post-training or following detraining at 25% and 50% femur length (SL; 12±13%, LL; 11±7%, LX; 13±11%). However, LL and LX groups had a greater significant (P<0.05) relative increase in muscle width at week 10 (LL; 26±13%, LX; 21±9%) compared to SL (13±8%) at 75% femur length. This was also the case at week 12, however only LL group was significantly greater (P<0.05) than SL group at this measurement site. Thigh girths increased following training at week 8 in all training groups and at all sites (mean over three sites SL; 3±2%, LL; 4±3%; LX; 4±2%), however this was not significantly different to baseline values (P>0.05) with no differences between groups. Thigh girths also did not differ significantly at weeks 10 or 12 compared to baseline or between groups.

to increase significantly in chronic response to the training protocols, with no significant difference between training groups at any knee angle (P>0.05, Figure 4). However, on further investigation, it was found that in fact, post-training there was a significant relative increase in activation at 50o (23±15%, P<0.05), 70o (26±15%, P<0.01) and 90o (16±13%, P<0.05) in the LX group and at 70o (24±9%, P<0.01) and 90o (25±9%, P<0.01) in LL group. In the SL group there

**Figure 3.** Oxygen consumption (VO2) during relative loading in SL (black bars), LL (white bars) and LX (grey bars). \*

**40 60 80**

**Relative Load (% 1RM)**

 decreased at week 10, and levelled off for the remainder of the detraining period (week 12) in both LL and LX groups with no significant changes compared to week 8. In the SL group, activation reduced at both weeks 8, 10 and 12 compared to baseline, however despite larger decrements in this group, there was no significant differences between all three training groups

*Muscle widths and thigh girths*; Changes in muscle widths are shown in Table 1. At week 8, VL muscle widths had increased significantly at all three measurement locations in all training groups compared to baseline (P<0.001). Following the first period of detraining at week 10, the SL group had returned to baseline values at all three measurement sites (P>0.05), however both LL and LX groups retained adaptations at this juncture relative to baseline (P<0.01). At week 12 LX group had returned to baseline levels at 25% and 50% width but still remained signifi‐ cantly hypertrophied at 75% femur length compared to baseline (P<0.05). The LL group retained their significant gains in muscle width at all three sites for the duration of detraining (P<0.01). There were no significant (P>0.05) mean relative changes between training groups

, although there were significant (P<0.05) reductions in VL

(-13±5%). Following detraining, muscle activation at

**\***

**\* #**

**\***

was no significant change at 50o

**0**

**2**

**4**

**VO2 (ml/ kg-1/ min-1)** 

**6**

**8**

**10**

**12**

**14**

162 Electrodiagnosis in New Frontiers of Clinical Research

(-15±6%) and 90o

Significantly different to 40% 1RM. # Significantly different to SL.

activation at both 70o

(Figure 6, P>0.05).

70o

**Figure 4.** Absolute Changes in VL activation at baseline (pre) and week 8 (post) training at 50o (black bars), 70o (white bars) and 90o (grey bars) knee flexion in A) SL, B) LX and C) LL groups.

**Figure 5.** Relative changes in VL activation at week 8 at three knee joint-angles in SL (black bars), LX (white bars) and LL (grey bars). \* Significantly different to baseline. # Significantly different to SL group.

Strength measures; 1RM in knee extension did not increase significantly compared to baseline until week 4 of the training program (data pooled, P<0.05) with each training group making similar increments in weight (SL; 11±4%, LL; 9±5%, LX 12±5%). There were further significant increases at week 6 (mean of groups 16±6%, P<0.01) and week 8 (mean of groups 22±8%, P<0.001), with no significant difference in the rate of relative increase in 1RM between groups (P>0.05). When muscle activation was normalised against torque at week 8 (Figure 7) as a marker for muscle efficiency, both LL and LX groups showed significantly better improved

**Figure 6.** Absolute changes in VL activation throughout training and detraining periods at 70o knee flexion. No signifi‐

and LX were not significantly different to each other in terms of the degree of muscle efficiency

Resistance training presents a medium through which muscular function can be enhanced. In order to devise an appropriate and effective resistance training program tailored with functional and structural enhancement objectives, it is necessary to understand the responses to both an acute bout of exercise, and the adaptations to exercise over a prolonged period of training. An important aspect for muscular performance is the degree to which the muscle can

of knee flexion, however there were no

following training (P>0.05). LL

or 70o

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muscle efficiency compared with SL (P<0.01) at 90o

cant were detected between phases or training groups (P>0.05).

increase.

**4. Discussion**

differences in muscle activation per unit torque at 50o


**Table 1.** Changes in Vastus Lateralis muscle width at each measurement site throughout training and detraining. \* Significantly different to baseline (P<0.05) \*\* Significantly different to baseline (P<0.01)

**Figure 6.** Absolute changes in VL activation throughout training and detraining periods at 70o knee flexion. No signifi‐ cant were detected between phases or training groups (P>0.05).

Strength measures; 1RM in knee extension did not increase significantly compared to baseline until week 4 of the training program (data pooled, P<0.05) with each training group making similar increments in weight (SL; 11±4%, LL; 9±5%, LX 12±5%). There were further significant increases at week 6 (mean of groups 16±6%, P<0.01) and week 8 (mean of groups 22±8%, P<0.001), with no significant difference in the rate of relative increase in 1RM between groups (P>0.05). When muscle activation was normalised against torque at week 8 (Figure 7) as a marker for muscle efficiency, both LL and LX groups showed significantly better improved muscle efficiency compared with SL (P<0.01) at 90o of knee flexion, however there were no differences in muscle activation per unit torque at 50o or 70o following training (P>0.05). LL and LX were not significantly different to each other in terms of the degree of muscle efficiency increase.
