Kinematic and electromyographic analysis of variations in Nordic hamstring exercise

Abstract

The purpose of this study was to present and biomechanically evaluate several variations of the Nordic hamstring exercise (NHE), achieved by altering the slope of the lower leg support and by asumming different hip flexion angles. Electromyographic and 2D kinematic measurements were conducted to analyse muscle activity (biceps femoris, semitendinosus, gluteus maximus, erector spine and lateral head of the gastrocnemius), knee and hip joint torques during 6 variations of NHE. The study involved 18 adults (24.9 ± 3.7 years) with previous experience in resistance training, but with little or no experience with NHE. Increasing the slope of the lower leg support from 0° (standard NHE) to 20° and 40° enabled the participants to perform the exercise through a larger range of motion, while achieving similar peak knee and hip torques. Instructions for increased hip flexion from 0° (standard NHE) to 25°, 50° and 75° resulted in greater peak knee and hip torque, although the participants were not able to maintain the hip angle at 50° nor 75°. Muscle activity decreased or remained similar in all modified variations compared to the standard NHE for all measured muscles. Our results suggest that using the presented variations of NHE might contribute to optimization of hamstring injury prevention and rehabilitation programs, by providing appropriate difficulty for the individual’s strength level and also allow eccentric strengthening at longer hamstring lengths.

Effects of eccentric training at long‐muscle length on architectural and functional characteristics of the hamstrings

“…Indeed, Hegyi et al 34 have recently demonstrated that the semitendinosus‐to‐BFlh activity ratio is higher during modified NHE (ie, hip flexed at 90°) compared with the standard NHE. It should be also noted that BFlh muscle activity during standard NHE (99.7% MVC) 7 is higher than during the modified NHE (80% MVC) 5 and the glider (50%‐60% MVC) 12 . Although we have added additional loads to both exercises during the intervention, it is possible that lower activity of BFlh in these exercises could have contributed to a smaller increase in BFlh muscle thickness.…”

“…The modified NHE was performed bilaterally in a custom‐designed device with adjustable slope of the lower leg support (S2P Ltd., Science to practice). The NHE device and the modified NHE variation were previously described by Sarabon et al, 7 who showed that adding hip flexion during the NHE can lengthen hamstrings at the time of peak knee and hip torque and peak hamstring electromyographic activity. Participants were instructed to maintain 75° of hip flexion during each repetition of the NHE.…”

“…These potential disadvantages could be solved with maintaining increased hip flexion during the NHE to enable strengthening in a lengthened position, as shown by Sarabon et al 7 Furthermore, in order to activate all biarticular hamstring muscles at lengths experienced during sprinting, a more holistic approach to hamstring training would require inclusion of both knee and hip‐dominant exercises at long‐muscle length 8 . However, such an approach to hamstring strengthening has been generally neglected in the scientific literature.…”

“…Contrary to isokinetic device, more accessible, feasible, and less time‐consuming exercises like the modified NHE 7 and the glider 9 could present a more practical approach for eccentric hamstring training in a lengthened position, while respecting its function as both knee flexor and hip extensor. Sarabon et al 7 have recently demonstrated that, compared with the traditional NHE, the modified NHE with hips flexed at 50‐75° allowed performing greater total ranges of motion with higher knee and hip joint torques. These conditions are likely to increase both the strain and the energy absorbed in MTUs of hamstring muscles.…”

The “Journal of Functional Morphology and Kinesiology” Journal Club Series: Highlights on Recent Papers in Corrective Exercise

“…In order to train greater knee extension angles, either assistance with resistance bands or cable machines or an increase in the slope of the lower leg support is recommended. These methods facilitate training at more specific muscle lengths while also increasing mechanical muscle loading (especially by increasing the time under tension) [ 12 , 13 , 14 ]. In general, prevention-oriented hamstring exercises performed at longer muscle lengths have been shown to be significantly better than conventional exercises [ 15 ].…”