Vertical ground reactions of two types of lunges according to foot axis

1

Keywords:

• Lunge performance
• ground reaction force
• joint powers

1. Introduction

Lunging is an integral part of the movement repertoire of competitive athletes in sports such as fencing, squash and badminton (Cronin et al. 2003). A lunge consists of a weight acceptance (braking) and recovery (accelerating) phase and forms an integral part of the start-stop recover cycle (Kuntze et al. 2010). In the present study, we investigate the kinetics difference obtained during a standard lunge (SL) and a ‘break-foot’ lunge (BFL) (Figure 1).

Figure 1. a) Standard lunge; b) ‘Break-foot’.

2. Methods

All data are presented as mean (SD). In this study, 8 elite players (21.4 (3.1) years; 177.6 (3.7) cm; 71.4 (3.9) kg) free of injury participated in this study with national and international experiences (8.1 (2.7) years). The experiment was approved by the local ethical committee.

A Kistler (Type 9286 A, Kistler, Switzerland) mobile multi-component force plate, integrated into the walkway, was used to record ground reaction force (GRF) at 500 Hz.

Participants were instructed to perform different lunges at different intensity (low, medium and high). Each participant performed four lunge tasks. The lunge was recorded after a run-in. Successful task consisted of correct foot placement at the lunge start line, dominant limb with the centre of the force plate and recovery to the starting position. Task order was randomized to mitigate order effects.

Assumptions of normality were verified using the Shapiro-Wilk W Test. The effect of types of lunges according to the velocity was assessed by a one-way ANOVA. All statistical analyses were performed with Statistica software (version 10; Statsoft, Inc., Paris, France). Statistical significance was set at p < 0.05.

3. Results and discussion

Mean GRF for SL and BFL are presented in Figure 2 for a representative participant. Following the classification by (Lees and Hurley 1994), five phases can be clearly identified in all lunges:

Figure 2. Vertical GRF in two different lunges. 1) Low velocity; 2) Moderate velocity; 3) High velocity.

1. Initial impact peak

2. Secondary impact peak

3. Amortization

4. Weight acceptance

5. Drive-off

Our results showed significant differences between the two types of lunge (p < 0.001). This is likely due to the initial contact with the ground made using two different ‘techniques’. During SL, the initial impact peak corresponds of the heel strike and the second impact peak corresponding of the movement of the foot to the toe (Hong et al. 2014). In SL condition, mean peak GRF reported is lower (∼189% of body weight) and comparable during BFL (∼225%) than previous studies by Kuntze et al. (2010) (∼225%) and Hong et al. (2014) (∼220–230%). However, typical forces were in excess compared to the study of Lees and Hurley (1994). This difference can be explained by the difference in movement magnitude between each study and a different sampling frequency used (100 Hz). Lunge movements appeared to be dynamically similar at the level of GRF (Kuntze et al. 2010).

Differently, during BFL used the medial side of the foot generated the initial impact peak and the stabilization with the lateral side generated the second peak. In addition, high impact forces are attenuated by eccentric action of knee and gastrocnemius (Jönhagen et al. 2009). Moreover, higher ground reaction is obtained during a BFL, suggesting a higher joint loading on the knee. In our knowledge, no study has analysed BFL (Table 1).

Table 1. Ground reaction force for both lunge at different velocity and different phases.

Velocity	a	b	c	d	e
Low SL	.92 (.31)	1.13 (.19)	1.01 (.16)	1.11 (.13)	1.29 (.18)
Low BFL	1.22 (.19)**	1.30 (.18)*	1.16 (.18)	1.15 (.16)	1.50 (.24)*
Δ%	24.6	13.1	12.9	3.5	14
Medium SL	1.28 (.10)	1.48 (.11)	1.32 (.17)	1.30 (.09)	1.53 (.11)
Medium BFL	1.45 (.12)**	1.38 (.09)	1.25 (.04)	1.24 (.08)	1.47 (.18)**
Δ%	11.7	−7.2	−5.6	−4.8	−4.1
High SL	1.89 (.30)	1.56 (.09)	1.36 (.12)	1.61 (.14)	1.64 (.18)
High BFL	2.25 (.14)**	1.71 (.14)*	1.36 (.06)	1.36 (.12)**	2.04 (.25)**
Δ%	16.1	8.8	0.0	−18.4	19.6

* p < 0.05;

** p < 0.01 between SL and BFL.

There were no significant differences during the amortization and the weight acceptance phase (except at high velocity) between different velocity by the fact that the entire foot is in contact with the ground. Complementary, during the deceleration of the lunge, a quasi-isometric action of the hamstrings assist of the deceleration and minimize forces placed upon the anterior cruciate ligament (Jönhagen et al. 2009). Thus, participants were able to apply larger vertical forces to the ground to maintain balance of the upper body. The weight acceptance phase exposes the lower limb to the greatest forces and rates of loading during SL.

There was significant difference during the drive-off phase (p < 0.01). The foot position is different for the two types of lunge during the acceptance phase resulting of a lower reaction force at push-off (Kuntze et al. 2010). Moreover, the non-dominant limb aids the dominant limb during this phase and reduces the vertical force. Furthermore, higher vertical loading rates is recorded during lunges and increased the risk of knee pain through the frontal and transverse planes.

4. Conclusion

This study compares two types of lunges according to the foot axis on a force plate. Based on our analysis, we found that the footstep has a great difference on the vertical ground reaction at the initial and secondary impact of the foot and on the drive-off. The coupling of eccentric and concentric muscle action is in line with stretch-shortening cycle tasks. The lunge can be separated in three phases: 1) weight acceptance (eccentric); 2) amortization (isometric); and 3) recovery (concentric). Finally, this study suggests that BFL produced higher ground reaction than SL and could increase joint loading on the patellar tendon.

Additionally, SL seems to reduce eccentric muscular contraction with lower values, thus reducing muscular fatigue and injury risk potential. Thus, during the initial impact phase, the force on the loading joint is more important during a BFL than SL during a short time. However, during the weight acceptance phases, BFL have lower values than SL but longer.