๐ŸŽพ Equipment Audit ยท Honest Review

5 Forearm Tools Every Tennis Player Considers. Here's What Each One Actually Gets Right โ€” and Where Each One Falls Short.

The FlexBar. The spring gripper. The Powerball. Resistance bands. If you've had tennis elbow or you're trying to prevent it, you've probably researched all of them. This is the honest breakdown โ€” what each tool does well, what it misses, and why the gap matters for tennis specifically.

Rob Callahan
4.5 USTA ยท Former tennis elbow sufferer ยท Equipment researcher  ยท  May 2026  ยท  10 min read

The honest answer: most of these tools work โ€” for the one thing they were designed for. The problem is that tennis elbow is a three-plane problem, and no single-plane tool fully solves it. That's the gap this audit is designed to show.

The Full Scorecard โ€” All 5 Tools Against Tennis-Specific Criteria

Tool Flexion / Extension Pronation / Supination Radial / Ulnar Progressive Overload Tennis Elbow Rehab Verdict
FlexBar (Tyler Twist) โœ“ Strong โœ— None โœ— None ~ Limited ~ Partial 1 of 3 planes
Spring Gripper โœ— None โœ— None โœ— None โœ“ Adjustable โœ— Wrong system 0 of 3 planes
Powerball / Gyroball ~ Partial โœ“ Moderate โœ— None โœ— Momentum-based โœ— Not progressive 1.5 of 3 planes
Resistance Bands โœ“ Good ~ Awkward โœ— None ~ Variable ~ Partial 1.5 of 3 planes
Dumbbell Wrist Curl โœ“ Good โœ— None โœ— None โœ“ Progressive ~ Partial 1 of 3 planes
โœ“ Gripzilla Tornado โœ“ Full โœ“ Full โœ“ Full โœ“ Adjustable friction โœ“ All 3 planes 3 of 3 planes

Every alternative tool covers at most one of the three wrist planes that tennis demands. The audit below explains exactly what each one does well โ€” and why the missing planes matter.

Tool 01 of 05

โš– Honest Verdict: The FlexBar< /span>

1. The FlexBar Is the Best-Researched Tool in Tennis Elbow Rehab โ€” and It Still Only Covers One Plane.

The FlexBar deserves its reputation. The Tyler Twist protocol โ€” gripping the bar in both hands and twisting in opposite directions to eccentrically load the wrist extensors โ€” is backed by peer-reviewed research and recommended by a significant portion of physiotherapists treating lateral epicondylitis. If you've done your research on tennis elbow, you've almost certainly been told to try it. That recommendation is not wrong.

 

But the FlexBar is a flexion/extension tool. It loads the extensor carpi radialis brevis eccentrically in one plane โ€” and that is exactly what it was designed to do. It does not load the pronators or supinators, and it does not train radial or ulnar deviation. For a player who has isolated flexion/extension weakness at the tendon insertion, it's effective. But for a tennis player whose elbow broke down through three-dimensional rotational loading across thousands of strokes, addressing one plane and leaving two untreated means the tendon's capacity still doesn't match the demand the game places on it.

 

The result is the pattern most long-term tennis elbow sufferers know: the FlexBar helps, pain reduces, they return to play โ€” and six months later they're back in the same position. The other two planes never caught up.

Flexion / Extension

โœ“ Covers

Pronation / Supination

โœ— Misses

Radial / Ulnar

โœ— Misses

"I used the FlexBar for eight months. Pain went down, I went back to playing, came back in four months with the same problem. My physio said I'd treated the symptom, not the whole deficit."

โ€” r/tennis user, 4.0 USTA, 2025

Tool 02 of 05

โœ— Honest Verdict: The Spring Gripper

2. The Spring Gripper Builds Grip Strength. Tennis Elbow Is Not a Grip Strength Problem.

The spring gripper is the most commonly purchased forearm tool โ€” and the one most likely to do nothing for tennis elbow, and potentially make it worse. It's compact, cheap, and intuitive: squeeze it, build your grip, get stronger. The problem is that grip strength โ€” the force produced by the finger flexors โ€” is a completely different system from the wrist extensors that degenerate in lateral epicondylitis.

 

Squeezing a spring gripper actually contracts the muscles on the opposite side of the forearm from where the tendinopathy lives. The extensor carpi radialis brevis, which is the tissue causing your lateral elbow pain, is not recruited by grip compression โ€” it's recruited by wrist extension and forearm rotation. Heavy grip work with a spring gripper can in fact increase the load on an already compromised tendon by recruiting adjacent forearm tissue and creating pull at the lateral epicondyle. It is, for many tennis elbow presentations, the wrong tool at the wrong time applied to the wrong system.

 

This is not the spring gripper's fault. It was designed to build grip, and it does that. The error is in thinking that grip strength and forearm health are the same thing โ€” they're not, and for tennis elbow specifically, treating them as interchangeable is a consistently repeated mistake.

Flexion / Extension

โœ— Misses

Pronation / Supination

โœ— Misses

Radial / Ulnar

โœ— Misses

Tool 03 of 05

โš– Honest Verdict: The Powerball / Gyroball

3. The Powerball Creates Rotational Load โ€” But It's Momentum-Based, Not Progressive. That's the Critical Difference.

The Powerball is the most misunderstood tool in this category. It does generate rotational resistance โ€” the gyroscopic mechanism produces a real pronation/supination load as the rotor spins. For wrist rehabilitation, it has legitimate applications, and players who use it report reduced elbow soreness compared to using nothing. The sensation of rotation is real. It's not a useless device.

 

The problem is control. Powerball resistance is momentum-dependent โ€” it increases as the rotor spins faster, which means the load is determined by how fast the user moves, not by a calibrated setting. This makes it very difficult to apply the graded, progressive overload that tendon rehabilitation requires. Tendons adapt to mechanical load best when that load can be precisely increased over time โ€” a protocol that requires the resistance to be reliable and controllable. The Powerball's feedback loop is essentially "spin faster for more resistance," which doesn't give the tendon the controlled loading curve it needs to rebuild collagen density systematically. It also doesn't cover radial and ulnar deviation at all.

 

For general wrist mobility and warm-up, it's fine. For structured tendon rehabilitation in the context of returning from tennis elbow, it lacks the progressive overload control the process requires.

Flexion / Extension

~ Partial

Pronation / Supination

โœ“ Moderate

Radial / Ulnar

โœ— Misses

"The Powerball felt like it was doing something but I had no idea if I was overloading or underloading the tendon. With tennis elbow, that uncertainty is a problem."

โ€” TennisWarehouse community forum, verified player, 2025

Why the Gap Exists in Every Alternative

Every tool above was designed for one plane. Tennis loads all three simultaneously on every shot.

Plane 1

Flexion / Extension

Drives topspin snap and backhand control. Covered by FlexBar, bands, and dumbbell curls โ€” but only in isolation.

Plane 2

Pronation / Supination

Drives serve power and forehand follow-through. Partially covered by Powerball โ€” but not with controllable progressive load.

Plane 3

Radial / Ulnar Deviation

Drives racket face stability on contact. Covered by zero alternative tools. This is the plane every competitor leaves completely unaddressed.

Tool 04 of 05

โš– Honest Verdict: Resistance Bands

4. Resistance Bands Are Versatile and Portable โ€” but They Apply Linear Force to a Rotational Problem.

Resistance bands are genuinely useful for shoulder and scapular work in tennis, and for general upper-body prehab. For forearm rehabilitation specifically, they're a reasonable starting point โ€” more so than grippers, slightly less so than the FlexBar โ€” because at least they can be configured to load the wrist extensors in a controlled way. Wrist extension against a band anchored underfoot does provide eccentric load to the relevant tendon. Physiotherapists use them in early-stage rehab for this reason.

 

The problem is that bands apply linear resistance along a single vector โ€” the direction of the band's pull. Wrist extension against a band is a straight-line exercise. Forearm rotation, radial deviation, ulnar deviation โ€” these require the resistance to rotate with the joint, which a band anchored to a fixed point cannot do. The more rotational the motion, the more the band goes slack or pulls in the wrong direction. Attempts to load pronation and supination with a band require awkward anchor positions that compromise both safety and load consistency. The result is a tool that does flexion/extension adequately and everything else poorly.

 

Bands are a useful addition to a complete protocol. They are not a complete protocol on their own โ€” and for the rotational demands of tennis specifically, they cover at most half of what needs to be trained.

Flexion / Extension

โœ“ Good

Pronation / Supination

~ Awkward

Radial / Ulnar

โœ— Misses

Tool 05 of 05

โœ“ Honest Verdict: Gripzilla Tornado

5. The Tornado Is the Only Tool That Loads All Three Planes Simultaneously โ€” With Adjustable, Progressive Friction.

The Tornado's mechanism is fundamentally different from every tool in this audit. Rather than resistance in a fixed direction, it uses adjustable friction applied through a ball-and-socket joint โ€” which means the resistance follows the wrist through any direction of motion. Flexion, extension, pronation, supination, radial deviation, ulnar deviation โ€” all of these can be trained in a single session with the same tool, at whatever friction level the tendon is ready for at that point in the protocol.

 

This matters for two reasons. First, it means all three planes of the tennis-specific wrist loading problem are addressed together, not in separate sessions with separate tools. Second, the friction can be dialled from near-zero (for early rehabilitation when the tendon is sensitive) to high resistance (for off-season loading above match-load levels). Progressive overload โ€” the core principle of tendon rehabilitation and strength adaptation โ€” is controllable, repeatable, and measurable. You know exactly what load you applied last session and you can precisely increase it this session.

 

The honest assessment: the Tornado does one job โ€” three-dimensional, progressive forearm loading โ€” and it does it better than anything else available for that specific purpose. It is not the cheapest option. It is not the tool with the most research attached to its brand name. It is the only tool that closes all three planes of the deficit that tennis creates in the forearm. That's the criteria that matters, and it's the one no alternative passes.

Flexion / Extension

โœ“ Full

Pronation / Supination

โœ“ Full

Radial / Ulnar

โœ“ Full

"I'd tried the FlexBar, bands, the Powerball. The Tornado was the first thing where I could feel all the right muscles working, not just one of them."

โ€” Chris W., 4.0 USTA, Tornado verified buyer

0 of 4

Alternative tools that cover all 3 wrist planes relevant to tennis elbow

Plane 3

Radial / ulnar deviation โ€” the plane zero alternatives address, and the one that controls racket face stability on contac

6 wks

Average time to measurable improvement on the full 3-plane protocol โ€” per Tornado user reports
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