Changes in running kinematics and kinetics after a 12-week running program for beginners

ABSTRACT

The effect of running training on running kinematics and kinetics in novice runners has not yet been investigated. Previous studies have shown that novice runners are less economical and more prone to injury compared to well-trained runners. Since running economy (RE) and running injury risk have been associated with biomechanical variables that may be trainable, the purpose of this study was to determine the effect of a 12-week training program for beginners on running kinematics and kinetics. It was hypothesised that participants would evolve towards running kinematics and kinetics that have previously been associated with better RE and lower injury risk. 27 participants underwent a full-body, three-dimensional running analysis before and after a 12-week running program. Outcome variables included peak joint angles, joint moments, and ground reaction forces (GRF) in three planes. After training, hip external rotation moment increased significantly with 0.01 Nm/kg. Peak vertical GRF decreased with 0.9 N/kg (4.05%). There were no significant changes in peak joint angles. In conclusion, results show that a 12-week running program for beginners aimed to increase running endurance does not lead to changes in running kinematics or kinetics that have previously been associated with better RE and lower injury risk.

KEYWORDS:

• Biomechanics
• training
• novice runners

Introduction

Running is a feasible and time-efficient way to become physically active. Therefore, running programs for beginners have become popular over the last decades. For most participants, the aim of these programs is to increase physical fitness and to improve running performance. In order to construct training programs that are optimal for improving running performance while minimising injury risks, it is important to understand the kinematic and kinetic adaptations that take place during a training program for beginners.

Running performance is, amongst other variables, influenced by maximal oxygen uptake (VO₂-max) and running economy (RE), which is defined as the oxygen consumption while running at a given speed. RE can be improved with a training intervention (Beneke & Hütler, 2005; Gonzalez-Mohino et al., 2016; Moore, Jones, & Dixon, 2012) and is therefore perceived as a ‘trainable’ parameter. It is known that well-trained runners have a better RE compared to untrained runners (Bransford & Howley, 1977; Morgan et al., 1995; Saunders, Pyne, Telford, & Hawley, 2004). In addition, it has been hypothesised that through a process of self-optimisation, runners develop a running gait that is most economical for them (Cavanagh & Williams, 1982). It is therefore likely that RE in novice runners will change with training.

RE is influenced by many biomechanical variables, including spatio-temporal variables, kinematics, kinetics, neuromuscular variables and storage of elastic energy. Optimal stride frequency and stride length (Cavanagh & Williams, 1982), a decrease in vertical oscillation of the centre of mass (Tseh, Caputo, & Morgan, 2008) and decreased leg extension at toe-off (Moore et al., 2012; Williams & Cavanagh, 1987), which can be achieved by a decrease in hip or knee extension, or less ankle plantar flexion, have been identified as good strategies to improve RE. Furthermore, an increased stride angle, which is defined as the angle of the parable tangent of the centre of mass at toe-off, has been associated with better RE (Santos-Concejero et al., 2014). Kinetic variables associated with better RE in experienced runners include a decrease in vertical peak impact force (Williams & Cavanagh, 1987), peak medio-lateral force (Williams & Cavanagh, 1987) and peak braking force (Kyröläinen, Belli, & Komi, 2001), as well as higher propulsive force (Moore et al., 2012) and increased leg stiffness (peak vertical GRF/centre of mass displacement during contact time; Dalleau, Belli, Bourdin, & Lacour, 1998). If RE improves with training, these variables are likely to change as novice runners become more experienced.

A recent review study has shown that untrained runners are at higher risk of developing overuse injuries compared to more experienced recreational runners (Videbaek, Bueno, Nielsen, & Rasmussen, 2015). Some biomechanical risk factors have been identified in the literature, which include increased hip internal rotation and adduction angle (Ferber, Noehren, Hamill, & Davis, 2010; Noehren, Davis, & Hamill, 2007), knee internal rotation (Noehren et al., 2007) and knee adduction angle, and ankle pronation (Willems, Witvrouw, De Cock, & De Clercq, 2007). These factors are possibly related to a lack in hip strength and endurance, which may increase with training. To our knowledge, there is no study that examines whether novice runners change their running style with training.

Longitudinal studies on changes in running biomechanics in novice runners are scarce. Moore et al. (2012) found that female novice runners ran with a less extended knee and ankle at toe-off after 10 weeks of training. Furthermore, they found that after training, the ground reaction force (GRF) vector was pointed more horizontally (Moore, Jones, & Dixon, 2016). Both variables were linked to a better running economy after training. However, Lake and Cavanagh (1996) found no change in running mechanics, which may be due to the short follow-up time of 6 weeks. Bailey and Messier (1991) found no change in stride length in 13 male novice runners after a 7-week training period, but stride length was the only biomechanical variable included in the study.

The aim of the present study was to study the influence of a 12-week running program on running kinematics and kinetics in beginner runners. A follow-up period of 12 weeks was chosen since this is a typical duration for a running program for beginners. It was hypothesised that participants would adopt a running pattern including characteristics that have previously been associated with lower injury risk and better running economy, such as decreased hip internal rotation and adduction angle and lower vertical peak impact forces. Insight in the natural adaptation processes following running training will help to improve training methods and running performance, and to reduce injury risk in beginner runners.

Methods

Participants

71 healthy participants were recruited for this study using flyers, social media and an advertisement in a local newspaper. Participants were included if they were between 18 and 60 years old, not obese (BMI below 30), and not doing any structural training in sports in the year prior to participation. Participants were excluded if they had sustained an injury to the lower limb in three months prior to participation. Participants signed informed consent prior to the first measurement. This study was approved by the ethics committee of the KU Leuven under approval number S55656.

Training program

The training program consisted of two supervised training sessions per week during 12 weeks. Participants were encouraged to do a third training session individually. Participants were allowed to choose between a training program that led from 1 to 30 minutes of continuous running, and a training program that led from 10 to 45 minutes of continuous running. Participants were instructed to run at a self-chosen, comfortable pace and were allowed to run in their own running shoes.

During the training program, participants kept a log book of their training sessions. In this log book, they were also instructed to note all pains, aches and possible injuries. In case of an injury, participants informed the researchers and were referred to a sports physician.

Measurements

Participants were tested within two weeks prior to and after finishing the 12-week running program. During testing, participants wore standardised, neutral running shoes (Asics Landreth 7®, Japan), provided by the researchers. 48 reflective markers were placed on anatomical landmarks of the participant’s body (Figure 1). Markers on the feet protruded through holes in the shoes, in order to measure the motion of the feet rather than the motion of the shoes. Marker trajectories were captured at 150 Hz. The marker model included 14 body segments: trunk, pelvis, left and right upper arm, lower arm + hand, thigh, shank, rearfoot, and forefoot + midfoot. Rearfoot motion was determined using a rigid heel cluster containing three markers, attached to the heel. The longitudinal axis of the rearfoot segment runs from the ankle joint centre (defined as the middle between the two malleoli) to the middle heel cluster marker and the horizontal axis between the malleoli. Motion of the forefoot segment was defined by the markers on the navicular bone, 1^st metatarsal head and 5^th metatarsal head. This multi-segment foot model was adopted from the study of Chard, Greene, Hunt, Vanwanseele, & Smith (2013).

Figure 1. Marker placement

After warming up on a treadmill (5 minutes walking, two minutes jogging at 1.94 m/s and two minutes running at self-selected speed), participants were instructed to run across the floor of the lab, in which a force platform (AMTI, type OR6-7, USA), capturing at 900Hz, was embedded. The participants were not aware of the presence of the force platforms and were instructed to keep their gaze straight ahead in order to prevent them from aiming to strike the force platform and altering their pace and/or stride length.

Data processing

For each participant, three successful trials from each test were selected for further analysis. A trial was considered successful if the participant’s entire foot was within the edges of the force plate and markers were sufficiently visible during a whole stride. Events (foot strike and toe-off) on the force plate were detected based on vertical GRF with a threshold of 10 N. Marker trajectories were filtered using a 4^th order low-pass Butterworth filter. Joint angles and moments were calculated in Vicon Bodybuilder version 3.6.1 (UK). Joint angles and moments were calculated with respect to the proximal segment. For the foot segments specifically, the two joints of the rearfoot (the talocrural joint and the subtalar joint) were considered as one single joint with the centre located midway between the markers on the medial and lateral malleoli. The forefoot angle was defined as the angle between the midfoot + forefoot segment and the rearfoot. Joint moments were normalised to body weight. Peak joint angles and moments were calculated for each trial and averaged over the three trials using Matlab version 2014a (Mathworks, USA). Other outcome variables included spatio-temporal parameters (running speed, stride length and contact time), peak GRF in three directions, loading rate and total stiffness. Instantaneous vertical loading rate (IVLR) and mean vertical loading rate (LR) were defined as the respectively the maximum and the mean slope of the vertical GRF curve between 20 and 80 percent of the interval between foot strike and impact peak (Milner, Ferber, Pollard, Hamill, & Davis, 2006). Total stiffness was calculated as the peak vertical GRF divided by the vertical movement of the centre of mass during the stance phase (Moore, 2016).

Statistical analysis

One leg per participant, being the leg with the best quality trials, was included in the statistical analysis. All dependent variables (peak joint angles, peak joint moments, peak GRF, running speed, stride length, contact time, LR, IVLR and total stiffness) were checked for normal distribution with a Shapiro-Wilk test. Differences between the pre- and post-test were analysed using a paired t-test for the normally distributed variables and a Wilcoxon signed-rank test for the not normally distributed variables. For the variables in which an overall training effect was found, a repeated measures ANOVA was used to determine the interaction effects between training and sex to detect possible different training responses between men and women. Also, the interaction effect of training and the training program that was followed was calculated to see if there was an effect of training group on training responses. All statistical analyses were done using SPSS version 20 (IBM, USA). Alpha level was set at 0.05.

Results

Out of the 71 recruited participants, 41 finished the training program. Out of these 41, only 27 participants were included in the present study due to technical problems with the force platform (Figure 2). 18 female and 9 male runners were analysed, with a mean age of 31 years (SD: 12), and a mean height of 174 cm (SD: 9). Mean weight of the participants was 70.7 kg (SD: 13.4) at the time of the pre-test and 71.1 kg (SD: 14.0) at the time of the post-test. There were no differences in sex, age, or weight between participants who finished the program and participants who dropped out.

Figure 2. Flowchart of the participants included in the study

Of the 27 participants, 14 chose the beginner training program, which led from 0 to 30 minutes of continuous running. Thirteen participants chose the more advanced program, leading from 10 to 45 minutes of continuous running. The older participants tended to choose the beginner program (average age 39, SD: 12 years), while the younger participants favoured the more advanced program (average age 25, SD: 7 years). On average, participants performed 27 (SD: 7) training sessions over the 12-week period. The preferred running speed did not change between the pre- and the post-test: mean speed of the pre-test was 2.87 m/s (SD: 0.31) and mean speed of the post-test was 2.85 m/s (SD: 0.35).

No changes in stride length, contact time, or centre of mass displacement were found. Changes in joint angles are shown in Table 1. No significant changes were found in peak joint angles after the running program (Figure 3). For peak joint moments, a significant increase in peak hip external rotation moment from 0.02 to 0.03 Nm/kg was found (Table 2). GRF in three dimensions are shown in Figure 4. There was no difference between pre- and post-test in medio-lateral or antero-posterior GRF. However, peak vertical GRF decreased from 23.1 (SD: 1.9) N/kg to 22.2 (SD: 1.8) N/kg (effect size = 0.52; p < 0.001). There was no interaction effect for time * sex or time * training program for peak vertical GRF. There were no differences in vertical impact peak, IVLR, LR, or total stiffness.

Table 1. Peak joint angles during the whole stride in degrees before and after a 12-week running program for beginners. *Non-parametric tested variable

Joint angle (°)		Pre	Post	Change	Effect size	p
Hip	flexion	40.9 ± 7	38.8 ± 8	−2.2 ± 6	−0.36	0.075
	extension	10.1 ± 4	10.5 ± 6	+0.5 ± 5	−0.10	0.623
	abduction	7.3 ± 3	7.1 ± 3	−0.2 ± 3	0.07	0.708
	adduction	12.0 ± 4	11.8 ± 3	−0.2 ± 3	−0.05	0.794
Knee	flexion	93.4 ± 11	91.7 ± 10	−1.6 ± 8	0.21	0.296
	extension	−3.0 ± 5	−2 ± 6	+1 ± 5	0.22	0.286
	abduction	7.1 ± 6	7.0 ± 6	−0.1 ± 7	0.01	0.952
	adduction*	6.7 ± 7	5.6 ± 5	−1.2 ± 6	−0.13	0.341
Forefoot	plantar flexion*	28.1 ± 8	29.3 ± 8	+1.2 ± 8	−0.09	0.523
	dorsiflexion*	24.0 ± 8	25.6 ± 6	+1.6 ± 7	−0.15	0.316
	eversion*	8.3 ± 4	9.1 ± 5	+0.7 ± 4	−0.12	0.412
	inversion*	7.6 ± 5	5.9 ± 5	−1.7 ± 5	−0.19	0.199
	abduction	20.8 ± 12	20.1 ± 10	−0.7 ± 10	−0.07	0.726
	adduction*	7.2 ± 8	5.9 ± 7	−1.2 ± 7	−0.19	0.191
Ankle	plantar flexion	26.3 ± 8	24.1 ± 10	−2.2 ± 7	0.30	0.176
	dorsiflexion	18.4 ± 8	21.2 ± 8	+2.8 ± 7	0.38	0.090
	eversion*	7.7 ± 9	8.1 ± 9	+0.3 ± 8	−0.07	0.638
	inversion	11.2 ± 7	12.8 ± 9	+1.6 ± 8	0.20	0.363
	abduction	22.2 ± 10	24.1 ± 9	+1.9 ± 11	0.17	0.439
	adduction*	4.7 ± 8	3.6 ± 9	−1.1 ± 8	−0.08	0.615

Table 2. Peak joint moments in N*m/kg before and after a 12-week running program for beginners. *Non-parametric tested variable. **significant difference: p < 0.05

	Joint moments (Nm/kg)	Pre	Post	Change	Effect size	p
Hip	flexion	0.64 ± 0.24	0.70 ± 0.18	+0.05 ± 0.17	0.32	0.108
	extension	0.78 ± 0.23	0.73 ± 0.24	−0.06 ± 0.26	0.21	0.276
	abduction	1.90 ± 0.22	1.87 ± 0.28	−0.03 ± 0.24	0.12	0.532
	adduction	0.11 ± 0.12	0.09 ± 0.11	−0.02 ± 0.11	−0.21	0.283
	internal rotation	0.38 ± 0.10	0.38 ± 0.09	+0.00 ± 0.10	0.04	0.830
	external rotation	0.02 ± 0.02	0.03 ± 0.02	+0.01 ± 0.02	−0.56	0.008**
Knee	flexion	0.21 ± 0.09	0.24 ± 0.08	+0.02 ± 0.08	−0.29	0.148
	extension	2.12 ± 0.41	2.18 ± 0.40	+0.06 ± 0.37	0.15	0.435
	abduction	0.54 ± 0.27	0.49 ± 0.34	−0.05 ± 0.36	0.14	0.458
	adduction*	0.08 ± 0.07	0.06 ± 0.05	−0.02 ± 0.07	−0.13	0.353
	internal rotation*	0.04 ± 0.02	0.04 ± 0.05	−0.00 ± 0.04	−0.05	0.694
	external rotation*	0.09 ± 0.07	0.09 ± 0.07	−0.00 ± 0.05	−0.04	0.751
Ankle	plantar flexion	1.95 ± 0.29	1.94 ± 0.29	−0.01 ± 0.27	0.04	0.842
	dorsiflexion*	0.16 ± 0.08	0.14 ± 0.07	−0.02 ± 0.05	−0.22	0.113
	eversion*	0.03 ± 0.04	0.04 ± 0.07	+0.01 ± 0.07	−0.10	0.439
	inversion*	0.26 ± 0.20	0.27 ± 0.16	+0.02 ± 0.15	−0.11	0.400
	abduction*	0.40 ± 0.37	0.33 ± 0.33	−0.07 ± 0.30	−0.17	0.220
	adduction*	0.12 ± 0.13	0.10 ± 0.12	−0.01 ± 0.10	−0.10	0.493

Figure 3. Comparison of the waveforms of joint angles [degrees] during the whole stride before (blue solid lines) and after (pink dashed lines) a 12-week training program for beginners. No significant changes in peak joint angles were found after training

Figure 4. Comparison of GRF in three directions before (blue solid lines) and after (pink dashed lines) a 12-week running program for beginners. A significant difference (*) in peak vertical GRF after training was found

Discussion and implications

This study aimed to determine the changes in running kinematics and kinetics after a 12-week training program for beginners. It was hypothesised that runners would change their running kinematics and kinetics towards a running style that, according to the literature, is more economical and less injury-prone.

After 12 weeks of running, no changes were observed in either of the spatio-temporal or kinematic variables. This indicates that participants did not change their stride length towards a more optimal stride length, as is suggested by Cavanagh & Williams as a strategy to improve RE (Cavanagh & Williams, 1982), or that they were already at their optimal stride length at baseline. Moore et al. (2012) found a decrease in knee extension and ankle plantar flexion at toe-off after a 10-week running program in 14 female beginner runners. This was suggested to be more economical because the muscles can operate at a point closer to the optimal on the force-length relationship, which causes a more efficient propulsion. These findings were not reproduced in the present study, even though the training programs were quite similar. In concordance with the present study, Lake and Cavanagh (1996) did not find any changes in running kinematics after a 6-week training program. Although the variables measured in the study of Lake & Cavanagh were limited to only sagittal plane joint angles on the left side of the body, some of these (shank angle at foot strike, ankle plantar flexion angle, knee flexion angle) are associated with RE. The authors suggested that 6 weeks of training would not be sufficient to cause changes in running mechanics. The present study confirms this and suggests that even a 12-week period may be too short.

An increase in hip internal exorotator moment was found after training (Table 2). Since excessive hip internal rotation is related to higher injury risk (Ferber et al., 2010; Noehren et al., 2007), which can be prevented by an increase in hip exorotator moment, this could be a positive adaptation. However, there was no change in the hip rotation angle after training. Furthermore, this peak external rotator moment occurred during toe-off, while the peak hip internal rotation angle (which is the risk factor) occurs during mid-stance. Therefore, further investigation is necessary to determine which factors lead to a decrease in injury risk as runners achieve a better training status.

A significant decrease in peak vertical GRF was found after the training program. This indicates that there is a redistribution of forces on the body after a 12-week running program: even though the differences may not be significant at joint level, they are present in the vertical GRF signal. There were no changes in the other planes, nor was there a change in GRF vector angle at peak propulsion, as was found by Moore et al. (2016). Unlike impact peak GRF, a lower peak vertical GRF is generally not associated with injury risk (van der Worp, Vrielink, & Bredeweg, 2016), although one cross-sectional study found a relationship between peak vertical GRF and a history of tibial and femoral neck stress fracture (Grimston, Engsberg, Kloiber, & Hanley, 1991) and one study found a relationship between peak vertical GRF and history of Achilles tendinopathy (McCrory et al., 1999). These two studies are outnumbered by studies that did not find an association between injury and peak vertical GRF, so careful interpretation with regard to injury risk is necessary.

Although performance was not measured objectively, data from the log books suggested that total weekly running time increased significantly and that participants were able to run much longer distances after 12 weeks of training. This self-reporting of training data is a limitation of this study, since participants may overstate their training efforts or report them inaccurately. Another limitation of this study was that the measurements were done in a lab setting, which is different from running outside. Especially with overground running in a motion lab, the participants might not reach their usual steady training pace due to space limitation. Finally, participants were measured in standardised, neutral running shoes, while they ran in their own shoes during the training program. This may have influenced the running kinematics slightly (Lilley, Stiles, & Dixon, 2013).

Conclusion

In conclusion, after a 12-week running program for beginners, we did not find significant changes in running kinematics or kinetics that could indicate a progression towards a more economical and less injury prone running style. This indicates that even in novice runners, running style is resistant to change when a running program designed solely to increase endurance is used. In order to change running technique in novice runners, added interventions such as strength training or technical drills may be necessary, although this remains to be further investigated.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by KU Leuven, under Grant LNE-SKBMW1-O2010.