Nordic Hamstring and Repeated-sprint Ability in Football (Soccer) Players

Study Overview
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Brief Summary
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The purpose of the study is to investigate the efficacy of a 10-week intervention, using the Nordic Hamstring exercise, on repeated-sprint ability in male sub-elite football players. The primary outcome measure is total sprint time during 4x6 sprint of 10 meters measured using dual-beam photoelectric cells. Additionally, eccentric knee flexor strength is measured using the Nordbord hamstring strength measure. The hypothesis is that strength training of the knee flexor muscles elicited by the Nordic Hamstring exercise will result in enhanced repetitive sprint-ability expressed as a decrease in total sprint time. Furthermore, baseline data is used to assess to correlation between eccentric hamstring strength and active hamstring flexibility AND sprint performance.

Official Title
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The Efficacy of a 10-week Intervention, Using the Nordic Hamstring Exercise, on Repeated-sprint Ability in Football (Soccer) Players - a Randomized Controlled Trial

Conditions
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Repeated-sprint Ability

Intervention / Treatment
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* Other: Nordic Hamstring
* Other: Control


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Sub-elite Danish football player Age 17-35. Able to participate fully in competitive football activities at the time of testing Exclusion Criteria: Hamstring pain resulting in loss of training and matches 2 months prior to study initiation. Specific systematic strength training of the hamstring muscles (>1/week) in the preceding 2 months before study initiation. Specific systematic sprint training (>1/week) in the preceding 2 months before study initiation. Longstanding injury (>6 weeks) in the lower extremities in the preceding 6 months to study initiation.

Ages Eligible for Study
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Minimum Age: 17 Years
Maximum Age: 35 Years

Sexes Eligible for Study
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Male

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Other
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Nordic Hamstring<br>The Nordic Hamstring group performs a progressive strengthening program (Mjolsnes et al., 2004) comprising of the Nordic Hamstring exercise during a period of 10 weeks. The training load increases from one session per week in week 1 to 3 sessions per week in week 3-10. Number of sets and repetitions progressively increase from 2 to 3 and 5 to 12, respectively. The exercise program is performed in the end of a regular football training session. | Other: Nordic Hamstring<br> <br> * Other names: Hamstring Curl;|
| Other: Control<br>The control group are asked not to perform the exercise or any other specific strength training for the hamstring muscles and to continue to play football as usual. | Other: Control<br> <br> |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Total sprint time measured during 4x6 sprints of 10 meters. The sprints are performed every 15s and the sets are separated by 3 minutes of rest. |  | Measured prior to and after the intervention period (at week 0 & 10) | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Single sprint times (best sprint time, sprint time during last sprint). |  | Measured prior to and after the intervention period (at week 0 & 10) | 
| Maximal eccentric knee flexor strength measured using Nordbord device |  | Measured prior to and after the intervention period (at week 0 & 10) | 
| Eccentric knee flexor strength endurance measured during 12 repetitions of the Nordic Hamstring exercise using Nordbord device. |  | Measured prior to and after the intervention period (at week 0 & 10) | 
| Active range of motion of hamstring muscles measured using inclinometer. |  | Measured prior to and after the intervention period (at week 0 & 10) | 
| Correlation between eccentric hamstring strength and active hamstring flexibility AND sprint performance. |  | Measured prior to the intervention (at week 0) | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Repeated-sprint ability, Nordic Hamstring exercise, Eccentric hamstring muscle strength