Abstract

Purpose:

We aimed to evaluate the acute physiological effects of high-load deadlift exercise on the lumbar intervertebral discs using MR diffusion-weighted imaging (DWI).

Methods:

Fifteen volunteers (11 men and 4 women; 23.2 ± 3.3 years) without lumbar intervertebral disc degeneration performed deadlift exercise (70% of 1 repetition maximum, 6 repetitions, 5 sets, 90 s rest between sets) using a Smith machine. Sagittal MR diffusion-weighted images of the lumbar intervertebral discs were obtained using a 1.5-Tesla MR system with a spine coil before and immediately after the exercise. We calculated apparent diffusion coefficient (ADC; an index of water movement) of the nucleus pulposus from diffusion weighted images at all lumbar intervertebral discs (L1/2 through L5/S1).

Results:

All lumbar intervertebral discs showed significantly decreased ADC values immediately after deadlift exercise (L1/2, −2.8%; L2/3, −2.1%; L3/4, −2.8%; L4/5, −4.9%; L5/S1, −6.2%; P < 0.01). In addition, the rate of ADC decrease of the L5/S1 disc was significantly greater than those of the L1/2 (P = 0.017), L2/3 (P < 0.01), and L3/4 (P = 0.02) discs.

Conclusion:

The movement of water molecules within the lumbar intervertebral discs is suppressed by high-load deadlift exercise, which would be attributed to mechanical stress on the lumbar intervertebral discs during deadlift exercise. In particular, the L5/S1 disc is subjected to greater mechanical stress than the other lumbar intervertebral discs.

Keywords: magnetic resonance diffusion-weighted image, intradiscal water movement, lumbar spine, lifting, mechanical stress

Introduction

A deadlift is a popular exercise that is frequently incorporated into athletic training programs. This exercise is effective in strengthening the back and lower extremity muscles, but the lumbar spine is subject to mechanical stress such as shear and compression forces during deadlift.^1–4 The stress is expected to become greater with increasing exercise weight. Therefore, the lumbar region is most susceptible to injury during high-load deadlift.^5,6 In addition, the repeated lifting of heavy weights has been identified as a risk factor for lumbar intervertebral disc degeneration/herniation.⁵ The lumbar intervertebral discs are thought to gradually degenerate through high-load deadlift training. However, to the best of our knowledge, little is known about the acute physiological changes of the lumbar intervertebral discs resulting from high-load deadlift exercise.

MRI has been used as a noninvasive method to investigate the status of the intervertebral discs in both clinical and experimental settings. In particular, diffusion-weighted imaging (DWI) can quantitatively evaluate the movement of water molecules (water

Acute Physiological Response of Lumbar Intervertebral Discs to High-load Deadlift Exercise

Osamu Yanagisawa, Tomoki Oshikawa, [...], and Koji Kaneoka

Additional article information

Abstract

Purpose:

We aimed to evaluate the acute physiological effects of high-load deadlift exercise on the lumbar intervertebral discs using MR diffusion-weighted imaging (DWI).

Methods:

Fifteen volunteers (11 men and 4 women; 23.2 ± 3.3 years) without lumbar intervertebral disc degeneration performed deadlift exercise (70% of 1 repetition maximum, 6 repetitions, 5 sets, 90 s rest between sets) using a Smith machine. Sagittal MR diffusion-weighted images of the lumbar intervertebral discs were obtained using a 1.5-Tesla MR system with a spine coil before and immediately after the exercise. We calculated apparent diffusion coefficient (ADC; an index of water movement) of the nucleus pulposus from diffusion weighted images at all lumbar intervertebral discs (L1/2 through L5/S1).

Results:

All lumbar intervertebral discs showed significantly decreased ADC values immediately after deadlift exercise (L1/2, −2.8%; L2/3, −2.1%; L3/4, −2.8%; L4/5, −4.9%; L5/S1, −6.2%; P < 0.01). In addition, the rate of ADC decrease of the L5/S1 disc was significantly greater than those of the L1/2 (P = 0.017), L2/3 (P < 0.01), and L3/4 (P = 0.02) discs.

Conclusion:

The movement of water molecules within the lumbar intervertebral discs is suppressed by high-load deadlift exercise, which would be attributed to mechanical stress on the lumbar intervertebral discs during deadlift exercise. In particular, the L5/S1 disc is subjected to greater mechanical stress than the other lumbar intervertebral discs.

Keywords: magnetic resonance diffusion-weighted image, intradiscal water movement, lumbar spine, lifting, mechanical stress

Introduction

A deadlift is a popular exercise that is frequently incorporated into athletic training programs. This exercise is effective in strengthening the back and lower extremity muscles, but the lumbar spine is subject to mechanical stress such as shear and compression forces during deadlift.^1–4 The stress is expected to become greater with increasing exercise weight. Therefore, the lumbar region is most susceptible to injury during high-load deadlift.^5,6 In addition, the repeated lifting of heavy weights has been identified as a risk factor for lumbar intervertebral disc degeneration/herniation.⁵ The lumbar intervertebral discs are thought to gradually degenerate through high-load deadlift training. However, to the best of our knowledge, little is known about the acute physiological changes of the lumbar intervertebral discs resulting from high-load deadlift exercise.

MRI has been used as a noninvasive method to investigate the status of the intervertebral discs in both clinical and experimental settings. In particular, diffusion-weighted imaging (DWI) can quantitatively evaluate the movement of water molecules (water diffusion) within the intervertebral disc by calculating an apparent diffusion coefficient (ADC). The intradiscal water movement is partially associated with intervertebral disc composition. Degenerated intervertebral discs show significantly lower ADC values than normal discs mainly due to reduced absolute intradiscal water content.^7–10 In addition, the intradiscal water movement is sensitive to mechanical stress placed on the intervertebral disc. It was confirmed using ovine lumbar intervertebral discs¹¹ or cadaveric human lumbar intervertebral discs¹² that the ADC value of the lumbar intervertebral disc decreases under compressive loads. Thus, the ADC value is thought to be a useful parameter for noninvasively evaluating the acute stress responses of the lumbar intervertebral discs to high-load deadlift exercise.

The purpose of this study was to investigate the acute physiological effects of high-load deadlift exercise on the lumbar intervertebral discs using MR DWI. The findings of this study would help to deepen our understanding of the mechanism by which the repeated lifting of heavy weights leads to lumbar intervertebral disc degeneration/herniation. We expected that the water movement within the lumbar intervertebral discs would decrease after high-load deadlift exercise as an acute stress response to repetitive mechanical stress.

Materials and Methods

Subjects

A total of 15 healthy volunteers (11 men and 4 women; mean age, 23.2 ± 3.3 years; age range, 19–30 years) with normal lumbar intervertebral discs participated in this study. The state of the lumbar intervertebral discs was assessed a few days before the measurement, according to the Pfirrmann scale¹³ for disc degeneration based on the  signal intensity (SI) on a midsagittal T₂-weighted MR image. Those with bulging, degenerated, and/or herniated discs were not included in this study. All of the participants were not regularly engaged in any sports activities at the time of measurement. No participants reported any pain and discomfort at the time of measurement and there was no previous history of surgery or injury in the lumbar region or lower extremities. Participants were instructed to refrain from any physical exercise beginning 48 h prior to the measurement.

This study was approved by the ethical committee of Waseda University and followed the ethical guidelines of the Declaration of Helsinki. Prior to the measurement, all participants were given a brief description of the study, the examination procedures, and the potential risks. Written informed consent was obtained from each participant.

 

Deadlift

After pre-exercise MRI measurements of the lumbar intervertebral discs, the participants performed a non-standardized warm-up including self-stretching and submaximal deadlift repetitions. The deadlift was performed without a weight belt using a Smith machine (Nautilus, Vancouver, WA, USA) (Fig. 1). The participants stood near the bar with a shoulder width stance on a stool placed in the Smith machine and squatted down to grasp the bar with an alternated grip, slightly wider than shoulder width with the arms straight and the hips lower than the shoulders. From the start position, they lifted a weight corresponding to 70% (69.2 ± 18.7 kg) of their 1 repetition maximum by extending the hips and knees and keeping the posture of the spinal column in a neutral position (a straight back), until a fully erect body position was established. Then, they lowered the bar maintaining the neutral spinal position. We instructed them to lift and lower the bar asnear to the body as possible. Verbal feedback regarding their deadlift technique was provided during the exercise. Each repetition was performed in a controlled manner by using a metronome with 2 s lifting and lowering phases. This 4 count action was repeated for 5 sets of 6 repetitions with a 90 s interval between sets, for a total of 30 repetitions.