Hamstring strain injuries (HSIs) remain common in various sports. The injury affects
the player’s well-being and may adversely impact team performance and the financial situation
of sporting organisations. Most HSIs occur during high-speed running, either in the
acceleration or the maximal velocity phase. Sprinting is a challenging task for the hamstrings
from biomechanical and neuromuscular perspectives. This observation has led to the
suggestion that sprinting biomechanics may be a hamstring strain injury (HSI) risk factor. Two
prospective studies have reported that participants who sustained a HSI had different sprinting
biomechanics compared to the participants who did not sustain a HSI, while other studies have
not found any differences. Overall, the evidence supporting the relationship between sprinting
biomechanics and hamstring strain injuries is scarce. Therefore, this doctoral thesis aims to
examine further the relationship between sprinting biomechanics and HSIs. The findings may
inform future research, rehabilitation protocols and HSI prevention strategies.
The first study was a narrative review that evaluated the scientific evidence
underpinning the potential link between sprinting biomechanics and HSIs. The aim of this
review was not only to summarise the current knowledge but also to examine the quality of the
available findings. Sixteen studies examining a wide range of biomechanical variables were
included. The biomechanical variables identified in the studies were ground reaction forces,
trunk and lower-limb joint angles, hip and knee joint moments and powers, hamstring muscle
tendon unit stretch, as well as surface electromyographic activity from various trunk and thigh
muscles. This review concluded that the overall quality of the articles was low and that the
current evidence could not provide a non-conflicting perspective on this issue. Moreover, the
review also highlighted the need for more quality research and provided some
recommendations to improve the quality of the research on sprinting biomechanics and HSIs.
The second study of this thesis explored expert opinion to identify the components of
sprinting technique believed to be risk factors for HSIs. Concept mapping was used to identify
components of interest that were determined the most important and actionable from the
perspective of the stakeholders. Concept mapping is a mixed-method participatory approach,
meaning that a qualitative approach was used to collect the data and a quantitative approach to
analyse them. This method involves four steps (i.e., preparation, brainstorming, structuring and
data analysis) that are all done in a dedicated web platform. We recruited practitioners (i.e.,
physiotherapists, strength and conditioning coaches, sport physician and sprint coaches) and
researchers who were considered experts if they had more than five years of experience in
professional or semi-professional sport organisations at h time of data collection. The
recruitment process was done through our professional network via emails and social media.
In total, twenty-three experts brainstormed to conclude that the five components of sprinting
technique believed to be a risk for HSIs were (in order of most to least important): training
prescription, neuromuscular and tendon properties, kinematics parameters/technical drills,
kinetics parameters and hip mechanics. The statement: “low exposure to maximal sprint
running” from the “training prescription” cluster received the highest mean importance and
confidence rating from the group of experts. This study also highlighted some discrepancies
between practitioners and researchers during the structuring step which suggests the need for
more research involving all the stakeholders.
The third study aimed to investigate if a previous HSI affects the lower limb’s joints’
biomechanical characteristics during sprinting. Participants were 23 male elite and sub-elite
Football (Soccer), Australian Rules Football, Rugby Union, and Rugby League players. Threedimensional motion capture and ground reaction force data informed a musculoskeletal model
to calculate the hip, knee, and ankle joint biomechanics variables via a “bottom-up” inverse
dynamics approach. The model output was calculated during two running conditions (i.e., high
acceleration and low acceleration). The uninjured participants had a speed of 4.76 ± 0.3 m.s-1
and an acceleration of 3.69 ± 0.6 m.s-2 during the high acceleration trials (ACCHi) while the
speed was 8.10 ± 0.6 m.s-1
and acceleration was 0.69 ± 0.4 m.s-2 during the low acceleration
trials (ACCLo). Injured participants had a speed of 4.77 ± 0.2 m. s-1
and acceleration time of
3.91 ± 0.6 m.s-2 during ACCHi while during ACCLo the speed was 8.14 ± 0.5 m.s-1
and
acceleration was 0.75 ± 0.5 m.s-2
. The average time since the HSI was 32.6 ± 36.0 months and
the average severity was 34.7 ± 22.0 days. The lower limb biomechanical characteristics of
participants with a history of HSI (n=13) were compared with those of participants with no
history of HSI (n=10). Nineteen discrete variables of interest were calculated, a majority of
which did not differ significantly between groups. Injured participants in the low acceleration
condition displayed a greater peak propulsive ground reaction force during the low acceleration
condition trials.
In conclusion, the data from this program of research will inform the direction of future
research on hamstring strain injury. This thesis highlighted the need for more quality research
involving all stakeholders. Additionally, this thesis may inform injury rehabilitation and injury
prevention strategies which should perhaps consider positive ground reaction force during
sprint running as a complementary element to monitor.”
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